Book of Abstracts

Eighteenth Conference on Electromagnetic & Light Scattering

Zhejiang University, Hangzhou city, Zhejiang province, China 10–14 June 2019

Edited by

Nadia Zakharova SciSpace, LLC New York, NY, USA © NASA 2019 All rights reserved outside of the United States; no part of this book may be reproduced or copied in any form or by any means – graphic, electronic, or mechanical, including photocopying, typing, or information storage and retrieval systems – without prior written permission of the copyright holder. Authors retain their individual rights and should be contacted directly for permission to use their material separately.

OBJECTIVE The 18th Electromagnetic and Light Scattering Conference (ELS-XVIII) was held at the Zhejiang University, Hangzhou city, Zhejiang province, China during the week of 10–14 June 2019. This conference followed the previous highly successful meetings held in Amsterdam (1995), Helsinki (1997), New York (1998), Vigo (1999), Halifax (2000), Gainesville (2002), Bremen (2003), Salobreña (2005), St.Petersburg (2006), Bodrum (2007), Hatfield (2008), Helsinki (2010), Taormina (2011), Lille (2013), Leipzig (2015), College Park (2017), and College Station (2018), as well as three closely related workshops held in Bremen (1996, 1998) and Moscow (1997). As with the other conferences, the main objective of the ELS-XVIII was to bring together scientists, engineers, postdocs, and PhD students studying diverse aspects of light scattering by particles and particle groups and thereby provide a stimulating atmosphere for thorough and comprehensive discussions of scattering theory, measurements, and practical applications.

SCOPE The specific topics covered by ELS-XVIII included (but were not limited to) the following: • new theoretical developments, numerical simulations, and laboratory measurements of light

scattering by nonspherical and morphologically complex particles and particle groups• detection and characterization of atmospheric particulates using laboratory, in situ, and remote

sensing techniques• scattering of light by terrestrial aerosols and clouds• scattering of light by oceanic particulates• scattering of light by solar system objects, exoplanets, and exoplanetary environments• scattering of light by various astrophysical objects• applications of light scattering methods in biology and biomedicine• light scattering in densely packed particulate media• near-field and coherent effects in light scattering, optical trapping, and manipulation• light scattering methods to control material properties and technological applications

INVITED PRESENTATIONS • Xiquan Dong, Baike Xi, Patrick Minnis, William Smith Jr, Norman Loeb, and Ping Yang, Can

active and passive instruments remotely sense the same clouds?• Oleg Dubovik, Pavel Litvinov, Tatyana Lapyonok, Fabrice Ducos, Xin Huang, David Fuertes,

Anton Lopatin, Yevgeny Derimian, Cheng Chen, Lei Li, Benjamin Torres, Yana Karol,Milagros Herrera, Jacques Descloitres, Stefan Amberger, Andreas Hangler, MichaelAspetsberger, and Christian Federspiel, Retrieval of aerosol properties from multi-angularPOLDER polarimetric observations

• Gérard Gouesbet, Generalized Lorenz-Mie theories and mechanical effects of laser light: a celebration of Arthur Ashkin’s pioneering work in optical levitation and manipulation

• Hiroshi Ishimoto, Satoru Adachi, and Kazuhiko Masuda, X-ray micro-CT imagery of deposited snow in optical modeling of atmospheric ice particles

• Michael Kahnert and Franz Kanngießer, Electromagnetic scattering by soot aerosols • Seiji Kato, Norman G. Loeb, Fred G. Rose, and David A. Rutan, Radiative transfer

computations in estimating surface and in-atmosphere radiation budget of Earth at a global scale

• Zhengqiang Li and Weizhen Hou, Directional Polarimetric Camera (DPC): Monitoring aerosol spectral optical properties over land from satellite observation

• Olga Muñoz, Jesús Escobar-Cerezo, Juan Carlos Gómez Martín, Daniel Guirado, and Fernando Moreno, Light Scattering Experiments at visible wavelengths

• Timo A. Nieminen, Anatolii V. Kashchuk, Isaac C. D. Lenton, Halina Rubinsztein-Dunlop, and Alexander B. Stilgoe, Direct optical measurement of force and torque in optical tweezers

• Fuzhong Weng, Yihong Duan, Jun Yang, Peng Zhang, Shouguo Ding, Chuanwen Wei, and Lei Bi, Advanced radiative transfer modeling system (ARMS) – a new generation of fast and accurate RT models in China

• Vladislav V. Yakovlev, Per aspera ad astra: getting light through highly scattering medium • Peng-Wang Zhai, Meng Gao, Bryan Franz, Jeremy Werdell, Yongxiang Hu, Kirk D.

Knobelspiesse, Brian Cairns, and Amir Ibrahim, Radiative transfer modeling of the hyperspectral and polarized reflectances for aerosol and ocean color remote sensing

CONVENERS Lei Bi, Zhejiang University, Hangzhou, China Michael Mishchenko, NASA GISS, New York, USA Jun Wang, University of Iowa, Iowa City, IA, USA Ping Yang, Texas A&M University, College Station, TX, USA PROGRAM COMMITTEE Gérard Gouesbet, National Institute of Applied Sciences, Rouen, France Joop Hovenier, University of Amsterdam, Amsterdam, The Netherlands Nikolai Khlebtsov, Russian Academy of Sciences, Saratov, Russia Gerhard Kristensson, Lund University, Sweden James Lock, Cleveland State University, OH, USA Hal Maring, NASA HQ, Washington, DC, USA M. Pinar Mengüç, Ozyegin University, Istanbul, Turkey Karri Muinonen, University of Helsinki & National Land Survey, Finland Christopher Sorensen, Kansas State University, Manhattan, KS, USA Gorden Videen, Army Research Laboratory, Adelphi, MD, USA Thomas Wriedt, University of Bremen, Germany Maxim Yurkin, Novosibirsk State University, Russia LOCAL ORGANIZING COMMITTEE Qunke Xia, Zhejiang University, Hangzhou, China Long Cao, Zhejiang University, Hangzhou, China

Weijun Li, Zhejiang University, Hangzhou, China Yang Du, Zhejiang University, Hangzhou, China Dawei Wang, Zhejiang University, Hangzhou, China Xiaoyu Zhang, Zhejiang University, Hangzhou, China

Invited Presentations Ordered alphabetically according to the first author’s last name

Can active and passive instruments remotely sense the same clouds?

Xiquan Donga, Baike Xia, Patrick Minnisb, William Smith Jrb, Norman Loebb,and Ping Yangc aUniversity of Arizona, 2880 Broadway, 1133 E. James E. Rogers Way, Tucson, AZ 85721, USA bNASA Langley Research Center, Mail Stop 420, 21 Langley Boulevard Hampton, VA. 23681,USA cTexas A&M University, College Station, TX 77843, USA

*Presenting author ([emailprotected])

It is a great challenge to derive true cloud fractions (CFs) from both active and passive remote sensing observations, and it is even more difficult to infer their vertical distributions globally and regionally. With the NASA Clouds and the Earth’s Radiant Energy System (CERES) Edition 4 cloud property products in conjunction with the availability of long-term DOE ARM ground-based and NASA CloudSat–CALIPSO spaceborne radar–lidar observations, we will tentatively answer the following two scientific questions: 1）Can space- and ground-based radar–lidar combinations observe the same types and amounts

of clouds over different climatic regions, such as those represented by the ARM SGP, NSA,ENA, and TWP sites?

2）Are clouds detected and analyzed using passive satellite remote sensing, such as in the CERESMODIS and GEO products, comparable to these actively sensed clouds over these four re-gions?

Our preliminary results show that the passively sensed CFs from CERES MODIS and GOES are approximately 10% lower than the CloudSat–CALIPO radar–lidar detected counterparts. This 10% difference is primarily due to the optically thin clouds detected by CALIPSO but not by passive remote sensors (MODIS and GOES). Comparing to ARM CFs, CERES-retrieved clouds have the same seasonal variations but CERES CFs are 5% and 7% lower than the ARM observa-tions at the ARM NSA and SGP sites, respectively. The CFs detected by the CloudSat–CALIPSO active sensors are 6.3% lower than ARM NSA observations because they missed some low-level clouds (below 1 km) over the Arctic. However, they are 2.3% higher than ARM SGP observations because CALIPSO can detect more optically thin high-level clouds. Therefore, knowing the limi-tation of platforms and retrieval methods, we have been endeavoring to uncover the physical mech-anisms underlying each measurement and retrieval method with the aid of multiple instruments on various platforms. In-depth analyses for ARM ENA and TWP sites are currently ongoing and will be presented at the ELX-XVIII.

Mode of presentation: Invited

Retrieval of aerosol properties from multi-angular POLDER polarimetric observations

Oleg Dubovika,*, Pavel Litvinovb, Tatyana Lapyonoka, Fabrice Ducosa, Xin Huanga,b, David Fuertesb, Anton Lopatinb, Yevgeny Derimiana, Cheng Chena, Lei Lia, Benjamin Torresa, Yana Karolb, Milagros Herreraa, Jacques Descloitresc, Stefan Ambergerd, Andreas Hanglerd, Michael Aspetsbergerd, and Christian Federspield aLaboratoire d’Optique Atmosphérique, UMR8518, CNRS – Université Lille, Villeneuve d’Ascq, France bGRASP-SAS, LOA, Université Lille 1, Villeneuve d’Ascq, France cICARE, CNRS, University of Lille, Villeneuve d’Ascq, France dCatalysts GmbH, High Performance Computing, Huemerstrasse 23, 4020 Linz, Austria

*Presenting author ([emailprotected])

Multi-angular polarimetric imagers are widely considered as the instruments that can provide most of the requisite information about global and regional properties of aerosol. Indeed, combined simultaneous spectral, angular, and polarimetric measurements of atmospheric radiation should maximize the sensitivity of observations to detailed aerosol properties. Numerous theoretical stud-ies concluded that multi-angular polarimetry can provide accurate characterization of aerosol with accuracy sufficient for many important applications. Nevertheless, the overall volume of polari-metric observations of the atmosphere remains small compared to that of photometric observa-tions. Furthermore, the currently available polarimetric observations are mostly considered as use-ful datasets for understanding the potential of polarimetry and for designing future missions rather than as aerosol information for specific climatological and environmental applications. This situ-ation is undoubtedly the result of the general complexity of polarimetric observations and the re-trieval theory. Polarimetry is highly sensitive to a large number of atmospheric parameters, and accounting adequately for all these sensitivities in the retrieval algorithm is very demanding, es-pecially in satellite applications wherein large volumes of data have to be processed. Therefore, the need to develop more robust algorithms for deriving aerosol properties from polarimetry has been clearly identified by the satellite community. As a result, several highly optimized algorithms have recently been developed and demonstrated to provide enhanced aerosol retrievals from sat-ellite polarimetry [1].

The main objective of this presentation is to discuss the achievements and challenges in provid-ing the accurate and complete aerosol retrievals from polarimetric observations. Specifically, 18 months of POLDER-1 and -2 and nine years of POLDER-3 observations have recently been pro-cessed with the GRASP algorithm [2,3] and provided to the community. In-depth analysis, vali-dation, and comparison with other data will be provided.

References [1] Dubovik, O., Z. Li, M. I. Mishchenko, et al., 2019: Polarimetric remote sensing of atmospheric aero-

sols:instruments, methodologies, results, and perspectives. J. Quant. Spectrosc. Radiat. Transfer 224,474–511.

[2] “Dubovik, O., T. Lapyonok, P. Litvinov, et al., 2014: GRASP: a versatile algorithm for characterizingthe atmosphere. SPIE Newsroom, DOI:10.1117/2.1201408.005558, http://spie.org/x109993.xml.

[3] Dubovik, O., M. Herman, A. Holdak, et al., 2011: Statistically optimized inversion algorithm for en-hanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations. At-mos. Meas. Tech. 4, 975–1018.

Mode of presentation: Invited

Generalized Lorenz–Mie theories and mechanical effects of laser light: a celebration of Arthur Ashkin’s pioneering work in optical levitation and manipulation

Gérard Gouesbet

CORIA-UMR 6614-Normandie Université, CNRS-Université et INSA de Rouen, Campus Universitaire du Madrillet, 76 800 Saint-Etienne du Rouvray, France ([emailprotected])

The generalized Lorenz–Mie theory (GLMT, more generally GLMTs) [1] had initially been developed to address issues in optical particle characterization, more particularly in optical particle sizing, in order to simultaneously measure velocities and sizes of individual particles embedded in flows, with applications to spray combustion or plasma spraying, among others. This line of research, however, has had two opportunities to meet with another line of research, namely the one by Arthur Ashkin dealing with optical levitation, trapping, and manipulation of macroscopic particles. The first opportunity has been that the GLMT (more generally the GLMTs) is able to deal with mechanical effects of light and indeed bridges the gap between the Rayleigh and ray-optics regimes to which the theoretical part of Ashkin’s work was limited. The second opportunity has been that optical levitation experiments promoted by Ashkin have been used to experimentally test the validity of the GLMT.

In this talk, as a celebration of Arthur Ashkin’s pioneering work concerning the mechanical effects of laser light, I shall offer a review and overview of the research devoted to the GLMTs and mechanical effects of laser light, both in Rouen where the GLMT had been developed, and all over the world.

Reference

[1] Gouesbet, G., and G. Gréhan, 2017: Generalized Lorenz–Mie Theories. Springer, Belrin.

Mode of presentation: Invited

X-ray micro-CT imagery of deposited snow in opticalmodeling of atmospheric ice particles

Hiroshi Ishimotoa,*, Satoru Adachib, and Kazuhiko Masudaa aMeteorological Research Institute, Nagamine 1-1, Tsukuba 305-52, Japan bNational Research Institute for Earth Science and Disaster Prevention, Snow and Ice Research Center,

Nagaoka 940-0821, Japan

*Presenting author ([emailprotected])

Cryogenic X-ray computed microtomography (micro-CT) is a powerful tool that can be used to analyze the detailed three-dimensional structure of deposited snow. To investigate the optical prop-erties of real snow particles, we developed a technique to extract individual shapes of snow parti-cles from X-ray micro-CT data, and we calculated their single-scattering properties using the con-ventional Geometrical Optics Method (CGOM) [1]. If we assume that the original shapes of fall-ing ice particles remain in a structure of new deposited snow, realistic models of some large ice particles in the atmosphere, such as snowflakes and graupels, are obtained from the micro-CT data. Moreover, the extracted shape data can be used for the modeling of inhom*ogeneous particles of an ice/water mixture by adopting numerical simulations of ice melting.

Microwave scattering properties for the modeled particles are calculated by applying the DDA or the FDTD method. On the other hand, the CGOM and the improved geometrical optics method (GOM2/GOIE) are basically applicable to the particles of large size parameters at visible and in-frared wavelengths, though some improvements for the numerical codes are necessary because of the two components for the particle material and of the complex shapes defined by a large number of facets. The approach of our particle modeling by using micro-CT data for the calculations of light scattering properties is discussed.

Reference [1] Ishimoto H., S. Adachi, S. Yamaguchi, T. Tanikawa, T. Aoki, and K. Masuda, 2018: Snow particles

extracted from x-ray computed microtomography imagery and their single-scattering properties. J.Quant. Spectrosc. Radiat. Transfer 209, 113–128.

Mode of presentation: Invited

Electromagnetic scattering by soot aerosols

Michael Kahnerta,b,* and Franz Kanngießerb

aResearch Department, Swedish Meteorological and Hydrological Institute, Folkborgsvägen 17, 601 76 Norrköping, Sweden

bDepartment of Space, Earth and Environment, Chalmers University of Technology, Maskingränd 2, 412 96 Gothenburg, Sweden

*Presenting author ([emailprotected])

Soot aerosols in the atmosphere are among the most important anthropogenic short-lived climate forcers that contribute to global warming. They can also cause respiratory health problems and degrade atmospheric visibility. The optical properties of these particles are of high interest in both climate modelling, remote sensing, and air-quality forecasting. However, modelling electromag-netic scattering by soot particles poses a formidable challenge on account of the particles’ mor-phological complexity and variability. Newly formed soot particles typically form relatively lacy fractal aggregates composed of small, (nearly) spherical monomers of amorphous carbonaceous material. After atmospheric aging, the aggregates become more compact and hydrophilic. This can lead to condensation of liquid-phase material, resulting in soot aggregates encapsulated in a shell of sulfate, organic material, water, salt, or mixtures thereof.

Modelling studies on the optical properties of soot often focus on (i) assessments of the impact of specific morphological features on the optical properties (e.g., [1]); (ii) attempts to achieve clo-sure of optical models and laboratory observations (e.g., [2]); and (iii) efforts to devise simple, yet accurate models that can be employed in environmental modelling and remote sensing (e.g., [3]). In this overview talk, the focus will be on the latter type, which, to a large extent, integrates results obtained from the former two types. The kinds of simplifications we can afford in a soot-optics model strongly depend on its intended use. Typically, we can introduce much more drastic simpli-fications in applications to climate modelling than in applications to remote sensing and chemical data assimilation. This will be illustrated in the talk by providing examples from each of these problems.

References [1] Liu, L., Mishchenko, M. I., and Arnott, W. P., 2008: A study of radiative properties of fractal soot

aggregates using the superposition T-matrix method. J. Quant. Spectrosc. Radiat. Transfer 109, 2656–2663.

[2] Kahnert, M., 2010: On the discrepancy between modeled and measured mass absorption cross sectionsof light absorbing carbon aerosols. Aerosol Sci. Technol. 44, 453–460.

[3] Kanngießer, F. and Kahnert, M, 2018: Calculation of optical properties of light-absorbing carbon withweakly absorbing coating: a model with tunable transition from film-coating to spherical-shell coating.J. Quant. Spectrosc. Radiat. Transfer 216, 17–36.

Mode of presentation: Invited

Radiative transfer computations in estimating surface and in-atmosphere radiation budget of Earth at a global scale Seiji Katoa,*, Norman G. Loeba, Fred G. Roseb, and David A. Rutanb aNASA Langley Research Center, Hampton, VA 23681-2199, USA bScience Systems and Applications, Inc., Hampton, VA, USA

*Presenting author ([emailprotected])

The NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project provides earth ra-diation budget data products. Top-of-atmosphere irradiances are derived from broadband radiance observations [1]. Surface and in-atmosphere irradiances are derived using a radiative model [2]. In order to understand radiation budget at a global scale, surface and in-atmosphere irradiances need to be estimated with a radiative transfer model.

Shortwave (solar) and longwave (emitted by the earth) irradiances are computed separately. The atmosphere is divided into ~50 vertical layers. Spectral region is separated into smaller spec-tral regions and absorptions by water vapor, ozone, carbon dioxide, and other trace gases are treated with the correlated-k approximation. Scattering by air molecules, aerosols and clouds are treated by two- and four-stream approximations applied to the integro-differential equation of ra-diative transfer. It is assumed that aerosol and cloud particles scatter radiation incoherently. Polar-ization state is ignored. Most inputs to the radiative transfer model come from observations, in-cluding temperature, humidity profiles, cloud and aerosol properties. Specifically, cloud and aer-osol properties used in the computations are derived from satellite observations of radiances meas-ured at discrete wavelengths.

Despite many approximations and assumptions made in the algorithm, computed surface irra-diances agree to within the uncertainty of surface irradiance observations taken at 36 land sites and 46 ocean buoys distributed globally when top-of-atmosphere irradiances are constrained by irra-diances derived from broadband radiance measurements by CERES instruments.

In this talk we summarize the method to compute surface and in-atmosphere irradiances, and how these irradiance estimates contribute to the understanding of the energy budget of the Earth and energy transport and hydrological cycle within the system.

References [1] Loeb, N. G., D. R. Doelling, H. Wang, W. Su, C. Nguyen, J. G. Corbett, L. Liang, C. Mitrescu, F. Rose,

and S. Kato, 2018: Clouds and the Earth Radiant Energy System (CERES) Energy Balanced and Filled(EBAF) Top-of-Atmosphere (TOA) Edition-4.0 data product. J. Climate 31, 895–918.

[2] Kato, S., F. G. Rose, D. A. Rutan, T. J. Thorsen, N. G. Loeb, D. R. Doelling, X. Huang, W. L. Smith,W. Su, and S.-H. Ham, 2018: Surface irradiances of Edition 4.0 Clouds and the Earth’s Radiant EnergySystem (CERES) Energy Balanced and Filled (EBAF) data product. J. Climate 31, 4501–4527.

Mode of presentation: Invited

Directional Polarimetric Camera (DPC): monitoring aerosol spectral optical properties over land from satellite observations

Zhengqiang Li and Weizhen Hou*

State Environment Protection Key Laboratory of Satellite Remote Sensing, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China

*Presenting author ([emailprotected])

The Directional Polarimetric Camera (DPC) is the first Chinese multi-angle polarized earth obser-vation satellite sensor, which will be launched onboard the GaoFen-5 Satellite in Chinese High-resolution Earth Observation Program [1]. GaoFen-5 runs in a sun-synchronous orbit with an in-clination angle of 98°, a 13:30 PM local overpass time, a 2-day revisiting period. The DPC em-ployed a charge coupled device detection unit with 512×512 effective pixels from the 544×512 useful pixels, realizing a spatial resolution of 3.3 km with a swath width of 1850 km. Furthermore, the DPC has three polarized channels (at 490, 670, and 865 nm) together with five non-polarized bands (at 443, 565, 763, 765, and 910 nm), and can obtain at least nine viewing angles by contin-uously capturing series images over the same target on orbit [2].

Based on the optimal estimation theory and improved bidirectional reflectance distribution function model, an inversion framework for the simultaneous retrieval of aerosol and surface pa-rameters is presented by taking full advantage of available radiometric and polarimetric measure-ments. The retrieved wavelength-independent fine-mode and coarse-mode aerosol volumes are used to assess the DPC performance on the inversion capability of spectral aerosol optical depth, from which the Ångström exponent and fine-mode fraction could be further obtained. In addition, based on the synthetic DPC data for various observation geometries, aerosol and surface types, the aerosol inversion capabilities are systematically evaluated, and the information content analysis results show that the aerosol spectral optical properties can be well retrieved over various land surfaces [2,3].

References [1] Gu, X., and X. Tong, 2015: Overview of China earth observation satellite programs. IEEE Geosci.

Remote Sens. Mag. 3, 113–129.[2] Li, Z., W. Hou, J. Hong, et al., 2018: Directional Polarimetric Camera (DPC): monitoring aerosol spec-

tral optical properties over land from satellite observation. J. Quant. Spectrosc. Radiat. Transfer 218,21–37.

[3] Zheng, F., W. Hou, and Z. Li, 2019: Optimal estimation retrieval for directional polarimetric cameraonboard Chinese Gaofen-5 satellite: an analysis on multi-angle dependence and a posteriori error. ActaPhys. Sin. 68, 040701.

Mode of presentation: Invited

Light Scattering Experiments at visible wavelengths

Olga Muñoza,*, Jesús Escobar-Cerezoa,b, Juan Carlos Gómez Martína, Daniel Guiradoa, and Fernando Morenoa aInstituto de Astrofísica de Andalucía (IAA), CSIC. Glorieta de la Astronomía sn, Granada 18008, Spain bDepartment of Physics, University of Helsinki, P.O. Box 64, FI00014, Finland

*Presenting author ([emailprotected])

Small solid particles are present in the atmospheres of planets, satellites, and comets in the form of aerosols, or cover their surfaces as regoliths. Dust particles absorb and scatter solar radiation and that coming from the surface affecting the atmospheric thermal structure. The strong de-pendence of the light scattered by those particles on their shape/structure, size and composition makes the measurements of the scattering pattern a powerful tool for particle characterization in remote sensing observations.

Over the last 10 years, the COsmic DUst LABoratory (CODULAB) [1] at the IAA-CSIC has produced an important number of high quality scattering matrices for clouds of randomly orient-ed cosmic dust analogues. The CODULAB measurements are performed at three different wave-lengths (448, 520, and 647 nm) covering the scattering angle range from 3° to 177°. The data are available in digital form in the Amsterdam–Granada light scattering database www.iaa.es/scattering [2]. In the database we combine the measurements from CODULAB and those previously obtained with the Amsterdam Light Scattering setup [3]. The samples presented in the database comprise a wide range of sizes (sub-micron up to mm-sized grains), shapes, and compositions. In this talk we will discuss our current efforts to disentangle the influence of size, shape, and composition on the scattering pattern measured in the lab to link remotely observed photo-polarimetric quantities at various wavelengths with dust properties. We will also present a set of test measurements intended for evaluating the performance of the experimental apparatus at the three wavelengths studied.

References [1] Muñoz, O., F. Moreno, D. Guirado, et al., 2011: The IAA Cosmic Dust Laboratory: experimental

scattering matrices of clay particles. Icarus, 211, 894–900.[2] Muñoz, O., F. Moreno, D. Guirado, et al., 2012: The Amsterdam–Granada Light Scattering Database.

J. Quant. Spectrosc. Radiat. Transfer 113, 565–574.[3] Hovenier, J. W., H. Volten, O. Muñoz, et al., 2003: Laboratory studies of scattering matrices for ran-

domly oriented particles. Potentials, problems, and perspectives. J. Quant. Spectrosc. Radiat. Trans-fer 79–80, 741–755.

Mode of presentation: Invited

Direct optical measurement of force and torque in optical tweezers Timo A. Nieminen*, Anatolii V. Kashchuk, Isaac C. D. Lenton, Halina Rubinsztein-Dunlop, and Alexander B. Stilgoe

The University of Queensland, Brisbane QLD 4072, Australia *Presenting author ([emailprotected]) A key contribution of optical tweezers to biology and biophysics, recognized by the award of the 2018 Nobel Prize in Physics to Arthur Ashkin, who invented optical tweezers in 1986 [1], has been the measurement of forces on the order of piconewtons in biological systems. There are two main routes to the measurement of forces. First, since the force depends on the position of the trapped particle, the force can be inferred from the position if this dependence is known. Especially in the case of small displacements such that the trap can be treated as a linear spring characterized by a spring constant, this dependence can be found. However, this requires a calibration for each type and size of particle, and needs to be repeated if the properties of the trap change.

The optical force results from the change in momentum of the trapping beam as it is scattered by the trapped particle. Therefore, measurement of the angular distribution of the scattered light allows the direct optical measurement of the force [2]. Most implementations of this make use of a per-particle calibration, but it is possible to calibrate a suitable detector once, and measure the force acting on arbitrary particles, even if the properties of the trap are changed.

In this talk we review the direct optical measurement of forces, including recent developments in calibrate-once methods. Noting that it is generally not possible to capture all of the scattered light, we discuss why, and to what extent, the forces can be accurately measured. We also consider the direct optical measurement of torque, which is straightforward in some cases [3], and a chal-lenge that has yet to be overcome in other cases. References [1] Ashkin, A., J. M. Dziedzic, J. E. Bjorkholm, and S. Chu, 1986: Observation of a single-beam gradient

force optical trap for dielectric particles. Opt. Lett. 11, 288–290. [2] Nieminen, T. A., H. Rubinsztein-Dunlop, and N. R. Heckenberg, 2001: Calculation and optical meas-

urement of laser trapping forces on non-spherical particles. J. Quant. Spectrosc. Radiat. Transfer 70, 627–637.

[3] Nieminen, T. A., N. R. Heckenberg, and H. Rubinsztein-Dunlop, 2001: Optical measurement of micro-scopic torques. J. Mod. Opt. 48, 405–413.

Mode of presentation: Invited

Advanced radiative transfer modeling system (ARMS) – a new generation of fast and accurate RT models in China

Fuzhong Wenga,*, Yihong Duana, Jun Yangb , Peng Zhang b, Shouguo Dinga,Chuanwen Weia , and Lei Bic

aState Key Laboratory of Severe Weather, No 46 Zhongguancun S. Ave., 100081, Beijing, China bNational Satellite Meteorological Center, No 46 Zhongguancun S. Ave., 100081, Beijing, China cZhejiang University, Zhejiang, China

*Presenting author ([emailprotected])

Many satellite instruments measure the radiation emitted by or reflected from the Earth at different spectral wavelengths. These observations – generally referred to as radiances – contain information about the Earth’s surface and atmosphere. Satellite radiances are not components of the atmos-pheric state vectors predicted by NWP models. In order for these radiances to be assimilated by the NWP models, a relationship between the model state vectors and the observed radiances is required. This relationship is derived from the forward radiative transfer model simulations (simply forward models) with the state vectors as input. In addition, the Jacobian vectors (or the derivative of radiance relative to the state vectors) are also needed in satellite data assimilation systems. For each satellite mission, a fast and accurate radiative transfer model is deemed neces-sary for the overall mission success. In the past two decades, the United States, Europe, and many other countries have already invested in the development of fast radiative transfer models through their space programs. These models have resulted in huge successes in uses of satellite data in operations.

In this presentation we review the current capabilities of fast radiative transfer models devel-oped in the numerical weather prediction community, summarize the full requirements on fast radiative transfer models for current and future satellite data assimilation, and propose new tech-niques for superfast computations of atmospheric and surface radiative transfer processes.

Mode of presentation: Invited

Per aspera ad astra: getting light through highly scattering medium

Vladislav V. Yakovleva,b,* a Texas A&M University, College Station, Texas 77843, USA b Zhejiang University, Hangzhou, Zhejiang, 310027, China

*Presenting author ([emailprotected])

Strong light scattering can make an optically non-absorbing object opaque. Many far-reaching applications, such as deep brain imaging, could greatly benefit from a better coupling of light into scattering medium and increased penetration depth resulting into greater transmission through a highly scattering medium. In this talk we discuss a simple, but efficient way of increasing light coupling through optical interface engineering [1–3]. Capitalizing on our prior work [4–9], we provide a theoretical foundation for our experimental findings and discuss potential applications for imaging and sensing [2,4,6–7].

This work was supported in part by the NSF (DBI-1532188 and ECCS-1509268) and DOD (FA9550-15-1-0517 and N00014-16-1-2578).

References [1] Thompson, J. V., B. H. Hokr, W. Kim, et al., 2017: Enhanced coupling of light into a turbid medium

through microscopic interface engineering. Proc. Natl. Acad. Sci. USA 114, 7941–7946.[2] Thompson, J. V., B. H. Hokr, W. Kim, et al., 2017: Enhanced optical coupling and Raman scattering

via microscopic interface engineering. Appl. Phys. Lett. 11, 201105.[3] Yamilov, A. G., R. Sarma, V. V. Yakovlev, and H. Cao, 2018: Coherent injection of light into an ab-

sorbing scattering medium with a microscopic pore. Opt. Lett. 43, 2189–2192.[4] Hokr, B. H., and V. V. Yakovlev, 2013: Raman signal enhancement via elastic light scattering. Opt.

Express 21, 11757–11762.[5] Hokr, B. H., J. N. Bixler, M. T. Cone, et al., 2014: Bright emission from a random Raman laser. Nat.

Commun. 5, 4356.[6] Hokr, B. H., J. N. Bixler, G. D. Noojin, et al., 2014: Single-shot stand-off chemical identification of

powders using random Raman lasing. Proc. Natl. Acad. Sci. USA 111, 12320–12324.[7] Thompson, J. V., G. A. Throckmorton, B. H. Hokr, and V. V. Yakovlev, 2016: Wavefront shaping

enhanced Raman scattering in a turbid medium. Opt. Lett. 41, 1769–1772.[8] Thompson, J. V., B. H. Hokr, and V. V. Yakovlev, 2016: Optimization of focusing through scattering

media using the continuous sequential algorithm. J. Mod. Opt. 63, 80–84.[9] Hokr, B. H., J. N. Bixler, G. Elpers, et al., 2015: Modeling focusing Gaussian beams in a turbid medium

with Monte Carlo simulations. Opt. Express 23, 8699–8705.

Mode of presentation: Invited

Radiative transfer modeling of the hyperspectral and polarized reflectances for aerosol and ocean color remote sensing

Peng-Wang Zhaia,*, Meng Gaob, Bryan Franzc, Jeremy Werdellc, Yongxiang Hud, Kirk D. Knobelspiessec, Brian Cairnse, and Amir Ibrahimb aJCET/Physics Department, University of Maryland Baltimore County, Baltimore, MD 21250, USA bSSAI, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA cNASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA dNASA Langley Research Center, Hampton, VA 23668 eNASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA

*Presenting author ([emailprotected])

Traditionally ocean color remote sensing relies on spaceborne spectrometers that view an image pixel with discrete spectral bands in only one viewing direction. A list of current ocean color sen-sors of this type include the Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIRS), Second Generation Global Imager (SGLI), and Geo-stationary Ocean Color Imager (GOCI), to name just a few. In order to further enrich the infor-mation content and characterize ocean biology and physiology better, the new generation of ocean sensors has evolved to include hyperspectral radiometers. In addition, co-located polarimeters have been proposed to better characterize aerosols and help atmospheric correction of ocean color sen-sors. One great example is the Ocean Color Instrument (OCI) that is planned to fly onboard NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission. The OCI is an advanced spectrometer that makes radiometric measurements with continuous spectral coverage from the ultraviolet (350 nm) to the near-infrared (890 nm), plus a set of discrete shortwave infrared bands (940, 1038, 1250, 1378, 1615, 2130, and 2260 nm). In addition, the PACE mission plans to include two multi-angle polarimeters: the UMBC Hyper Angular Rainbow Polarimeter (HARP-2) and the SRON Spectro-polarimeter for Planetary Exploration (SPEXone).

Radiative transfer modeling is an important tool for interpreting the advanced hyperspectral images and polarization measurements. In this talk we will present a vector radiative transfer pack-age for coupled atmosphere and ocean systems that can be used for the aerosol and ocean color retrieval using co-located spectroradiometer and polarimeter data. The package is flexible in both atmospheric and ocean compositions, includes both elastic and inelastic scattering, and incorpo-rates atmospheric gas absorptions. The radiative transfer code has been used to study the sensitivity of the hyperspectral measurements in response to different atmospheric and ocean configurations. It is particularly interesting to study the different contributions of hyperspectral water leaving sig-nals to the top-of-atmosphere measurements for different ocean water types, phytoplankton fluo-rescence strength, and most interestingly, non-photochemical quenching effects. Moreover, we will also present our current effort of retrieving aerosol and ocean color information simultane-ously using polarimeter data, and use that information in assisting the atmospheric correction of hyperspectral ocean color observations. We will present the properties of aerosols and water leav-ing radiances retrieved from the airborne Research Scanning Polarimeter data and share the lessons that we have learned from this retrieval activity.

Regular Presentations Ordered alphabetically according to the first author’s last name

Light scattering studies of composite interstellar dust analogues using computer simulation and laboratory setup Gazi A. Ahmeda,*, Manash J. Boruaha, and Ankur Gogoib

aDepartment of Physics, Tezpur University, Tezpur 784028, Assam, India bDepartment of Physics, Jagannath Barooah College, Jorhat 785001, Assam, India

*Presenting author ([emailprotected])

Dust particles found in the interstellar medium have been reported to be composed of amorphous silicate, graphite, amorphous carbon, carbonates, metal oxide grains, amorphous ice particles and even nanodiamonds. Study of the light scattering properties of such dust particles by using both computer simulations and laboratory experiments (with analogue samples) provide significant information for interpreting scattered light signals from unknown interstellar dust particles. Here we report the study done on light scattering by interstellar dust analogue mixtures of graphite and fayalite at three incident wavelengths, that is, 543.5, 594.5, and 632.8 nm, using two computational models for particle sizes ranging from 0.3 μm to 5.0 μm. The scattering and extinction efficiencies, single scattering albedo, asymmetry parameter, phase function and degree of linear polarization are calculated using the Discrete Dipole Approximation. A comparative analysis of the theoretical and experimental results of phase function and polarization shows that the percentage composition of a mixture model is very important while simulating interstellar dust particles. The developed computational models are successful in representing a two species mixture of interstellar dust analogues dispersed in both shapes and sizes. This technique can be applied to interpret observed astrophysical data, to study atmospheric aerosols and in remote sensing.

References [1] Boruah, M. J., and G. A. Ahmed, 2018: Visible light scattering properties of irregularly shaped silica

micro particles using laser based laboratory simulations for remote sensing and medical applications.Laser Phys. 28, 015701.

[2] Boruah, M. J., A. Gogoi, B. C. Nath, and G. A. Ahmed, 2017: Light scattering studies of randomlyoriented polycrystalline fayalite micro particles as interstellar dust analogues. J. Quant. Spectrosc.Radiat. Transfer 196, 213–221.

[3] Boruah, M. J., A. Gogoi, and G. A. Ahmed, 2016: Laboratory simulation and modeling of size, shapedistributed interstellar graphite dust analogues: a comparative study. Planet. Space Sci. 125, 27–36.

Preferred mode of presentation: Oral

Optimization of the discrete dipole approximation applied to particles on a plane substrate

Anna E. Akhmetyanovaa,b,* and Maxim A. Yurkina,b aVoevodsky Institute of Chemical Kinetics and Combustion, SB RAS, 3 Institutskaya Str., 630090

Novosibirsk, Russia bNovosibirsk State University, 1 Pirogova Str., 630090, Novosibirsk, Russia

*Presenting author ([emailprotected])

Investigating optical properties of particles on a substrate is relevant to different scientific and technical applications. On one hand, the synthesis and use of various nanoparticles commonly occur on a substrate. On the other hand, the substrate and/or interface itself enables one to develop new optical methods, for example, total internal reflection microscopy. The discrete dipole approximation (DDA) is an efficient method for simulating the interaction of the electromagnetic field with particles of arbitrary shape and internal structure. This method, derived from the frequency-domain volume-integral Maxwell equation, is numerically exact, i.e., achieves any required accuracy with sufficient computational resources.

The computational problem of the DDA consists in solving a large system of linear equations. High efficiency is achieved by applying a conjugate-gradient iterative solver with the matrix-vector product computed using the fast Fourier transform (FFT). The presence of the substrate requires one to replace the dipole–dipole interaction term with a more complicated expression including the so-called Sommerfeld integrals. The latter lacks a translational symmetry along the surface normal, seemingly breaking the FFT acceleration. Fortunately, this acceleration can be retained by cleverly rearranging the interaction terms [1]. This new formulation has been implemented in the open-source code ADDA [2], reaching the same computational complexity as in the free space (almost linear in the number of dipoles). Still, the calculation of four Sommerfeld integrals for every possible distance between two dipoles takes significant time, in some cases longer than the rest of the simulation.

The goal of this work is to optimize these calculations by using series expansions and asymptotic approximations of the integrals for small and large distances, respectively, and an interpolation over two cylindrical variables in the intermediate region. This approach significantly reduces the number of runs of the integration routines and, consequently, the simulation time, while keeping the same accuracy. We will present specific timing results and simulation examples at the conference.

References [1] Yurkin, M. A., and M. Huntemann, 2015: Rigorous and fast discrete dipole approximation for particles

near a plane interface J. Phys. Chem. C 119, 29088–29094.[2] Yurkin, M. A., and A. G. Hoekstra, 2011: The discrete-dipole-approximation code ADDA: capabilities

and known limitations. J. Quant. Spectrosc. Radiat. Transfer 112, 2234–2247.

Preferred mode of presentation: Oral

Remote sensing of droplet size profiles in cumulus clouds using the Research Scanning Polarimeter: tests on simulated data

Mikhail D. Alexandrova,b,*, Daniel J. Millerc, Chamara Rajapakshed, Ann Fridlindb, Bastiaan van Diedenhovena,b, and Brian Cairnsb

aColumbia University, 2880 Broadway, New York, NY 10025, USA bNASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA cNASA Goddard Space Flight Center, Greenbelt, MD 20771, USA dUniversity of Maryland, Baltimore County, 1000 Hilltop Cir, Baltimore, MD 21250, USA

*Presenting author ([emailprotected])

The Research Scanning Polarimeter (RSP) is an airborne along-track scanner measuring the po-larized and total reflectance in nine spectral channels. Its uniquely high angular resolution allows for the characterization of liquid water cloud droplet sizes using the rainbow structure observed in the polarized reflectance over the scattering angle range from 135° to 165°. We use two separate retrieval techniques. The first one is a parametric fit assuming that cloud droplet size distribution (DSD) has gamma-distribution shape and yielding its effective radius and variance. The second one, the non-parametric Rainbow Fourier Transform (RFT), is able to provide the entire DSD shape with no pre-assumptions. The RSP’s high angular resolution and frequency of measurements also allows for the estimation of cumulus cloud shape and position from the collection of view-lines tangent to the cloud surface.

In this study we introduce retrievals of vertical profiles of droplet size made along the illumi-nated side of the cumulus cloud. First, we use the RSP’s tangent view-lines to determine the posi-tion of the cloud surface. Then for each point on the bright side of this surface we aggregate view-lines passing through it, thereby constructing the polarized reflectance corresponding to that point (as a function of scattering angle). The rainbow part of this reflectance is analyzed yielding the shape and parameters of the cloud DSD. Finally, the retrievals made for all available points on the cloud surface are combined into vertical profiles.

This profiling algorithm was tested by simulating RSP measurements over LES-generated clouds using the MSCART 3D RT code. Towering cumulus clouds were selected for this numeri-cal experiment in preparation for analyses of real RSP measurements during the upcoming Cloud, Aerosol and Monsoon Processes Philippines Experiment. The results of the comparison between the virtual RSP retrievals and the actual microphysical parameters in the LES model show agree-ment in the effective radius and variance within 1 μm and 0.02, respectively. Also, the non-para-metric RFT algorithm was able to detect and characterize two different populations of cloud drop-lets: one convectively rising from cloud bottom to top, while growing in size; and the other being activated at cloud top due to condensation and consisting of small 5-μm particles. This opens the way to process-oriented remote sensing based on the RSP data.

Preferred mode of presentation: Oral

The application of realistic dust grain shapes to debris disk photometry

Jessica A. Arnolda,*, Alycia J. Weinbergera,*, Gorden Videenb, and E. Zubkoc aCarnegie Institution for Science, Department of Terrestrial Magnetism, 5421 Broad Branch Rd, Wash-

ington, DC 20015, USA bSpace Science Institute, 4750 Walnut St, Suite 205, Boulder, CO 80301, USA cFar Eastern Federal University, 8 Sukhanova Street, Vladivostok 690950, Russia

*Presenting author ([emailprotected])

Debris disks are dusty circ*mstellar disks analogous to our solar system’s Kuiper belt, asteroid belt, and zodiacal cloud [1]. The dust in these disks is produced by the destruction of comets, asteroids, and protoplanets. Understanding the composition of the material within these extrasolar systems may provide insight into the planet formation process. At visible and near-infrared (VNIR) wavelengths, dust within debris disks is detected via light from the host star scattered by these dust grains. As debris disks are typically too cold to produce key identifying silicate spectral features in thermal emission near 10 μm [2], scattered light in the VNIR wavelength range is important for making compositional determinations. To interpret scattered light observations of debris disks we need to model the light scattering properties of the constituent dust, which depend on grain com-position, size, and structure. Often these models assume compact, spherical particles (e.g., [3]), although other grain shapes such as ellipsoids and distributed hollow spheres have been considered (e.g., [4]). We use the discrete dipole approximation method [5,6] to calculate scattering efficien-cies for realistic grain shapes [6] and use these to model the optically thin disk AU Microscopii.

References [1] Hughes, A. M., G. duch*ene, and B. C. Matthews, 2018: Debris disks: structure, composition, and var-

iability. Annu. Rev. Astron. Astrophys. 56, 541–591.[2] Matthews, B. C., A. V. Krivov, M. C. Wyatt, et al., 2014: Observations, modeling and theory of debris

disks. In Protostars and Planets VI, University of Arizona Press, Tucson, AZ, pp. 521–544.[3] Kruegel, E., and R. Siebenmorgen, 1994: Dust in protostellar cores and stellar disks. Astron. Astrophys.

288, 929–941.[4] Min, M., J. W. Hovenier, and A.de Koter, 2003: Shape effects in scattering and absorption by randomly

oriented particles small compared to the wavelength. Astron. Astrophys. 404, 35–46.[5] Draine, B. T., and P. J. Flatau, 1994: Discrete dipole approximation for scattering calculations. J. Opt.

Soc. Am. A 11, 1491–1499.[6] Zubko, E., D. Petrov, Y. Shkuratov, et al., 2005: Discrete dipole approximation simulations of scatter-

ing by particles with hierarchical structure. Appl. Opt. 44, 6479–6485.

Preferred mode of presentation: Oral

Study of stochastic processes with time-dependent transition probabilities

J. C. Atenco-Cuautle*, I. Cazares-Aguilar, E. J. Alvarado-Letechipia,and G. Martinez-Niconoffa

Instituto Nacional de Astrofisica, Optica y Electronica INAOE, Dpto. de Optica, Postal 51 y 216, Puebla, Mexico

*Presenting author ([emailprotected])

In this work we show applications in the evolution of probabilistic trajectories when the transition probabilities acquire a stationary character which is interpreted as “probabilistic geodesics”.

The evolution of the stochastic process type Markov chain is described when transitions of probability are functions of time. The structure of the process is modeled with a stochastic matrix whose convergence generates stationary trajectories. The model is implemented to the synthesis of optical modes allowing to describe the processes of entanglement and revival of the fields them-selves. The fields evolution is describing by the entropy calculus. Computational simulations are shown as results.

Considering families of trajectories, morphological variability of optical fields is described, generating coherence and partial polarization processes.

Reference [1] Coleman, R., 1974: Stochastic Processes. Springer, Berlin.

Preferred mode of presentation: Poster

Electromagnetic interactions of anisotropic dye molecules surrounding a nanosphere

Baptiste Auguié* and Eric C. Le Ru

School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600 Wellington, New Zealand

*Presenting author ([emailprotected])

Nanostructures such as metal colloids can substantially affect the absorption and emission of light by vicinal molecules, raising considerable interest for such diverse applications as light-harvesting in solar cells, or surface-enhanced spectroscopies. The topic is also of great relevance to more fundamental pursuits such as strong coupling between light and molecules. Recent experimental results have revealed that molecular absorption can undergo considerable spectral changes when a molecule is adsorbed on a metal surface [1]. Such changes may be attributed to a variety of causes, some of a more chemical nature – a modification of the molecule interacting with the metal surface – and some that fall in the realm of classical electromagnetic scattering.

This contribution will present an original and rigorous computational model to describe the electromagnetic interactions between collections of anisotropic dye molecules and a core nano-sphere in experimentally-relevant configurations. Our model extends the coupled-dipole approxi-mation, which predicts important effects of orientation-dependent dye-dye interactions in a hom*o-geneous medium [2], with a rigorous multipolar description of dye-nanosphere interactions based on a generalised multipolar Mie theory [4]. The predictions of this model reveal a rich interplay between the relative orientation of the dye molecules, their concentration, and their interaction with the metallic core that strongly modifies the local electric field, in amplitude and polarisation. The model qualitatively confirms the results of a simpler core-shell approximation where the dyes are described as a hom*ogeneous effective-medium shell [1,3], but provides a much finer micro-scopic description of dye-dye interactions for different relative dye orientations and distances, and better insights into the subtle effects of dye-nanoparticle electromagnetic interactions.

References [1] Darby, B. L., B. Auguié, M. Meyer, A. E. Pantoja, and E. C. Le Ru, 2016: Modified optical absorption

of molecules on metallic nanoparticles at sub-monolayer coverage. Nat. Photon. 10, 40–45.[2] Auguié, B., and E. C. Le Ru, 2018: Optical absorption of dye molecules in a spherical shell geometry.

J. Phys. Chem. C 122, 110–115.[3] Tang, C., B. Auguié, and E. C. Le Ru, 2018: Modeling molecular orientation effects in dye-coated

nanostructures using a thin-shell approximation of Mie theory for radially anisotropic media. ACS Pho-ton. 5, 5002–5009.

[4] Auguié, B., B. L. Darby, and E. C. Le Ru, 2019: Electromagnetic interactions of dye molecules sur- rounding a nanosphere (submitted).

Preferred mode of presentation: Oral

Plasmonic responses of metallic/dielectric core–shell nanoparticles on a dielectric substrate Dilan Avşara, Hakan Ertürka, and M. Pinar Mengüçb,* aBoğaziçi University, Department of Mechanical Engineering, Bebek, 34342 Istanbul, Turkey bCenter for Energy, Environment and Economy (CEEE), Özyeğin University, 34794 Istanbul, Turkey *Presenting author ([emailprotected]) Core–shell nanoparticles can be classified as dielectric–metal, metal–dielectric, and metal–metal according to their material compositions for the core and shell, respectively. These nanostructures have various advantages: the plasmonic response of the nanoparticles can be tuned and/or hybrid-ized by changing the material composition, core/shell size ratio, and the surrounding medium. Such nanoparticles can offer unprecedented ways to exploit their optical properties with optimum field enhancement and tunable LSPR responses [1]. Their hybrid structures are promising for lo-calized heating applications that necessitate a detailed study of absorption mechanisms with ma-terial and size combination.

Although there are numerous numerical studies based on NPs and their LSPR responses, most of them based on geometries involving free space without surface interactions or in an aggregate form. A recent numerical study of silica core-gold shell NP being placed on a BK7 substrate showed that enhanced absorption efficiency and a redshift of the plasmon response can be achieved for selective heating and nano-manufacturing purposes [2]. There are, however, limited number of studies on material comparisons that will guide the experimentalists to the optimum configurations for the enhanced effects. The objective of the present paper is to focus on the spectral absorption profiles of core–shell nanoparticles with various core–shell material and size configurations ac-companied with surface interactions. Current study is the follow-up investigation of [2] with single core–shell nanoparticle placed on a semi-infinite BK7 glass substrate being illuminated by an EM light from bottom with total internal reflection. The spectral absorption behavior of core–shell nanoparticle is numerically studied with selected metal–dielectric, and dielectric–metal pairs for core and shell materials, respectively.

In this paper, the effects of material selection on the plasmonic response and local absorption are evaluated for core-shell nanoparticles placed over a BK7 glass substrate. Eight different core-shell pairs are studied using the vectorized version of discrete dipole approximation with surface interactions. Two classes of dielectric core–metallic shell and metallic core–dielectric shell parti-cles are considered. It is shown that core–shell structures with dielectric materials can have ab-sorption enhancement compared to the bare metallic nanoparticles. Moreover, it is observed that core–shell pairs yield multipeak localized surface plasmon resonance (LSPR) response due to their hybrid structure. Absorption enhancement and LSPR tuning ranges are shown with different die-lectric materials that can be used in localized heating of designated core–shell NPs placed over a surface for nanomanufacturing purposes. In order to determine the optimum size configurations, a number of core-shell pairs are explored with specified volumetric filling ratio of core materials.

References [1] Strobbia. P., E. Languirand, and B. M. Cullum, 2015: Recent advances in plasmonic nanostructures for

sensing: a review. Opt. Eng. 54,100902 [2] Talebi Moghaddam, S., H. Ertürk, and M. P. Mengüç, 2016: Enhancing local absorption within a gold

nano-sphere on a dielectric surface under an AFM probe. J. Quant. Spectrosc. Radiat. Transfer 178, 124–33

Preferred mode of presentation: Oral

Reversal of optical binding force between uniaxial anisotropic heterodimer based on the forced breaking of symmetry J. Bai, Z. S. Wu*, and C. X. Ge

School of Physics and Optoelectronic Engineering, Xidian University, Xi’an, Shaanxi, 710071, China Collaborative Innovation Center of Information Sensing and Understanding at Xidian University, Xi’an,

Shaanxi, 710071, China *Corresponding author ([emailprotected])

This study theoretically investigates the optical binding force exerted on uniaxial anisotropic het-erodimer induced by an arbitrarily polarized high-order Bessel beam (HOBB). Such non-diffract-ing light suppressed the influence of the axial intensity profile of the illuminating beams on the self-organization process which then depended critically upon the inter-particles interactions. Us-ing the generalized multi-particle Mie equation (GMM) [1,2], we analyzed the lateral binding force in terms of Maxwell’s stress tensor for various inter-particle distance at some specific wavelengths. The stimulating connection between the reversal of near-field binding force of uniaxial anisotropic heterodimer and the role of symmetry-breaking has not been investigated comprehensively in the literature. In this work, the symmetry of spherical uniaxial anisotropic heterodimer-setup is broken forcefully by shining the light from a specific side of the set-up instead of impinging it from the top. We demonstrate that for the forced symmetry-broken spherical heterodimer-configurations: reversal of lateral and longitudinal near-field binding force follow completely distinct mechanisms. Interestingly, the reversal of lateral binding force can be easily controlled changing the direction of light propagation or by varying their relative orientation. Besides, the polarizations of incident HOBB considerably influence the optical binding force of uniaxial anisotropic nanoparticles. In binding uniaxial anisotropic nanoparticles, the polarization of incident beams should be chosen in accordance with the anisotropic permittivity tensor elements. This simple process of controlling binding force may open a novel generic way of optical manipulation even with the anisotropic heterodimers of other shapes. Though it is commonly believed that the reversal of near-field bind-ing force should naturally occur for the presence of bonding and anti-bonding modes, our study based on Lorentz-force dynamics suggests notably opposite proposals for the aforementioned cases. Observations in this article can be very useful for improved sensors, particle clustering and aggregation. References [1] Gouesbet, G., and G. Gréhan, 1999: Generalized Lorenz–Mie theory for assemblies of spheres and

aggregates. J. Opt. A. Pure. Appl. Opt. 1, 706–712. [2] Gouesbet, G., L. Mees, and G. Gréhan, 2002: Generic formulation of a generalized Lorenz–Mie theory

for pulsed laser illumination. In Laser Techniques for Fluid Mechanics, Springer, Berlin, pp. 175–188. Preferred mode of presentation: Poster

Temperature dependence of ice particle refractive index and implications in sub-millimeter ice cloud retrievals Adam Bella,*, Ping Yanga, and D. L. Wub aTexas A&M University, College Station, TX 77843, USA bClimate and Radiation Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA *Presenting author ([emailprotected]) Ice clouds play a substantial role in the Earth’s climate system, particularly through their influence on the global energy budget. These influences, coupled with the spatiotemporal variability of ice clouds, impose difficulties in understanding their radiative effects and subsequently our current climate and potential future changes [1]. Fundamental ice cloud parameters for quantifying cloud radiative properties are the ice water path (IWP) and ice particle effective diameter. Current gen-eral circulation models vary in their estimation of the cloud IWP by as much as an order of mag-nitude. Imposing constraints from observations is challenging since ice mass retrievals are gener-ally ill conditioned (i.e., less information content in observations than in the requisite solution). Sub-millimeter (sub-mm) wave radiometry is an emerging technique for characterizing cloud properties due to high sensitivity to ice cloud parameters, in particular the IWP.

Even with this increased sensitivity, it is necessary to make assumptions in ice cloud retrievals, such as ice particle shape (habit) which effects particle single scattering properties. Previous stud-ies have also shown sensitivity of ice particle sub-mm single scattering properties to ice refractive index at certain temperatures [2,3].

In this work we present an information content based approach to understand temperature ef-fects on ice refractive index, and subsequent contributions to ice cloud property retrieval uncer-tainties over a wide range of sub-mm wavelengths. References [1] Xie, X., and J. Maio, 2011: Polarization difference due to nonrandomly oriented ice particles at milli-

meter/submillimeter waveband. J. Quant. Spectrosc. Radiat. Transfer 112, 1090–1098. [2] Tang, G., P. Yang, and D. L. Wu, 2015: Sensitivity study of ice crystal optical properties in the 874

GHz submillimeter band. J. Quant. Spectrosc. Radiat. Transfer 187, 416–421. [3] Ding, J., et al., 2016: Single-scattering properties of ice particles in the microwave regime: temperature

effect on the ice refractive index with implications in remote sensing. J. Quant. Spectrosc. Radiat. Transfer 190, 26–37.

Preferred mode of presentation: Poster

Advances in digital holography of aerosol particles Matthew J. Berga,*, Ramesh Giria, Yuli Heinsonb, Osku Kemppinena, Ryan Mersmanna, Jesse Laninga, Steve Hollerc, and Gorden Videend,e,f aKansas State University, Department of Physics, 1228 N. 17th St., Manhattan, KS 66506-2601, USA bDepartment of Energy, Environment & Chemical Engineering, Washington University in Saint Louis,

One Brookings Dr., Box 1180, Saint Louis, MO 63130, USA cDepartment of Physics and Engineering Physics, Fordham University, Bronx, NY 10458-5198, USA dSpace Science Institute, 4750 Walnut Street Suite 205, Boulder, CO 80301, USA eDeptartment of Astronomy and Space Science, Kyung Hee University, 1732, Deogyeong-daero, Giheung-

gu, Yongin-si, Gyeonggi-do 17104, South Korea fU.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783, USA *Presenting author ([emailprotected]) Digital holography has proven a powerful method to study aerosol particles. In the method, a par-ticle is illuminated by an expanded laser beam and the interference pattern produced by unscattered and forward-scattered light from the particle is recorded on a sensor such as a CCD. This interfer-ence pattern is the hologram, and from it, an image of the particle can be unambiguously rendered. However, we have recently shown that other useful information may be obtained from a particle’s hologram [1,2]. For example, we will explain here how the two-dimensional angular scattering pattern in the far-field can be generated from the hologram via Huygens’s principle [2]. We will also discuss our ongoing laboratory and instrument-development work applying digital holography to atmospheric aerosols [3]. References [1] Berg, M. J., N. R. Subedi, and P. A. Anderson, 2017: Measuring extinction with digital holography:

Nonspherical particles and experimental validation. Opt. Lett. 42, 1011–1014. [2] Giri, R., C. Morello, Y. W. Heinson, O. Kemppinen, G. Videen, and M. J. Berg, 2019: Generation of

aerosol-particle light-scattering patterns from digital holograms. Opt. Lett. 44, 819–822. [3] Berg, M. J., Y. W. Heinson, O. Kemppinen, and S. Holler, 2017: Solving the inverse problem for

coarse-mode aerosol particle morphology with digital holography. Sci. Rep. 7, 9400. Preferred mode of presentation: Oral

The invariant imbedding approach to the Debye series for light scattering by nonspherical particles Lei Bia*, Feng Xub, and Gérard Gouesbetc

aDepartment of Atmospheric Sciences, Zhejiang University, Zhejiang, China bJet Propulsion Laboratory, California Institute of Technology, USA cCORIA-UMR 6614-Normandie Université, CNRS-Université et INSA de Rouen, Campus Universitaire

du Madrillet, 76 800 Saint-Etienne du Rouvray, France

*Presenting author ([emailprotected])

The Debye series was first proposed for light scattering by an infinite circular cylinder [1]. It has been demonstrated to be valuable for optical interpretation of light scattering by spheres, coated spheres, and spheroids (e.g., [2–4]). By applying the extended boundary condition method (EBCM) [5,6] and expanding the Green’s dyadic into the third and fourth vector spherical wave functions, Xu et al. [7,8] derived the Debye series for a hom*ogeneous and coated nonspherical particle. However, like the EBCM-based T-matrix method for computing light scattering by nonspherical particles, the EBCM-based Debye series approach has similar numerical convergence issues in calculating light scattering when the particle size and/or aspect ratio (e.g., for spheroid) gets large. In this talk, we report the progress in using an invariant imbedding approach (IIA, [9]) to compute the Debye series for a large nonspherical particle. The IIA has been successfully applied to compute the T-matrix for large nonspherical particles [10] and found to be also applicable in the framework of the Debye series. First, we show that the T-matrix can be explicitly expanded in terms of an infinite series. To compute the IIA-based Debye series, we derive four matrices associated with the reflection and transmission of wave interaction upon the boundary from the medium to the particle and from the particle to the medium. Second, we demonstrate that the four matrices satisfy the Riccati differential equations which can be solved by the Runge–Kutta method. The results are analytically validated for a sphere and numerically validated for nearly spherical particles (against the results computed by the EBCM-based Debye approach). Finally, the new insights into light scattering by nonspherical particles gained from the Debye series approach are illustrated with representative examples, such as the optical interpretation of light backscattering by nonspherical particles.

References [1] Debye, P., 1908: Das elektromagnetische Feld un einen Zylinder und die Theorie des Regenbogens.

Phys. Z. 9, 775–778.[2] Lock, J. A., 2016: Linear system approach to the Debye series for electromagnetic scattering by a

multi-layer sphere: a tutorial. J. Quant. Spectrosc. Radiat. Transfer 178, 38–49.[3] Bi, L., P. Yang, G. W. Kattawar, and M. I. Mishchenko, 2015: Optical tunneling of arbitrary

macroscopic 3D objects. Phys. Rev. A 92,013814.[4] Bi, L., F. Xu, and G. Gouesbet, 2018: Depolarization of nearly spherical particles: the Debye series

approach. Phys. Rev. A 98, 053809.[5] Waterman, P. C., 1965: Matrix formulation of electromagnetic scattering. Proc. IEEE 53, 805–812.

[6] Mishchenko, M. I., and L. D. Travis., 1998: Capabilities and limitations of a current FORTRANimplementation of the T-matrix method for randomly oriented, rotationally symmetric scatterers. J.Quant. Spectrosc. Radiat. Transfer 60, 309–324.

[7] Xu, F., J. A. Lock, and G. Gouesbet, 2010: Debye series for light scattering by a nonspherical particle.Phys. Rev. A 81, 043824.

[8] Xu, F. J. A. Lock, and G. Gouesbet, 2010: Debye series for light scattering by a coated nonsphericalparticle. Phys. Rev. A 81, 063812.

[9] Johnson, B. R., 1988: Invariant imbedding T-matrix approach to electromagnetic scattering. Appl.Opt. 27, 4861–4873.

[10] Bi, L., and P. Yang, 2014: Accurate simulation of the optical properties of atmospheric ice crystalswith invariant imbedding T-matrix method. J. Quant. Spectrosc. Radiat. Transfer 138, 17–35.

Preferred mode of presentation: Oral

Measurement of the aspect ratio distribution of rigid arbitrary shaped nanoparticles using theTranslational–Rotational Image-based Dynamic Light Scattering

Paul Briarda,*, Chen Yuan Lib, and Xiao Shu Caib aXidian University, 2 South Tai Bai Road, 710071 Xi’an, P. R. China bUniversity of Shanghai for Science and Technology, 516 Jun Gong Road, 130012 Shanghai, P. R. China

*Presenting author ([emailprotected])

The Dynamic Light Scattering method (DLS) is a method which permits to measure the Stokes radius distribution of a sample of polydisperse arbitrary shaped nanoparticles in Brownian motion, where the Stokes radius of a particle is the radius of the spherical particle which have the same translational Brownian motion [1]. In a conventional DLS experiment, the sample is illuminated by an incident focused laser beam and scatters the light toward a photomultiplier tube. The analysis of the light fluctuations recorded by the photomultiplier tube permits to obtain the distribution of their translational diffusion coefficients. Then, the Stokes radius distribution is measured.

The DLS has been improved in the Ultrafast Image-based Dynamic Light Scattering method (UIDLS) where the fluctuation of the light scattered by the sample is recorded by an image sensor instead of a photomultiplier tube [2,3]. Although the Stokes radius is related with the size, the conventional DLS or by the UIDLS don’t permit to obtain information about the shape of the nanoparticles. This is the reason why we have developed an improvement of the UIDLS, named Translational–Rotational Image-based Dynamic Light Scattering where the light scattered by the sample is recorded by two cameras for two polarization geometries. From the light fluctuations recorded by the cameras, the translational diffusion coefficient distribution and the rotational dif-fusion coefficient distribution are measured. They are related with the translational and rotational Brownian motion of the nanoparticles and they permit to obtain the aspect ratio distribution of the arbitrary shaped nanoparticle complimentarily with the Stokes radius distribution which is also measured. This talk will be focused on the experimental measurement of the aspect ratio distribu-tion of a sample of 2D nanoparticles, where the aspect ratio a 2D nanoparticle is defined as the aspect ratio of the disk-like particle which have the same translational and rotational Brownian motion.

References [1] Berne B. J., and R. Pecora, 2000: Dynamic Light Scattering With Applications to Chemistry, Biology

and Physics. Dover Publications, New York.[2] Zhou W., J. Zhang, L. Liu, and X. Cai., 2015: Ultrafast image-based dynamic light scattering for nano-

particle sizing. Rev. Sci. Instrum. 86, 115107.[3] Zhang D., X. Cai, and W. Zhou, 2018: Two dimensional self-adapting fast Fourier transform algorithm

for nanoparticle sizing by ultrafast image-based dynamic light scattering. Particuology 41, 74–84.

Preferred mode of presentation: Oral

Lidar depolarization ratio for soot fractal aggregates: application to tropospheric and stratospheric smoke

Romain Ceolatoa,*, Lucas Pauliena, Matthew J. Bergb, William R. Heinsonc,Anna Gialitakid, Alexandra Tsekerid, Vassilis Amiridisd, and Chris Sorensenb aONERA, The French Aerospace Lab, Toulouse FR 31055, France bKansas State University, Department of Physics, 1228 N. 17 St., Manhattan, KS 66506-2601, USA cWashington University in St. Louis, 1 Brookings Drive, St. Louis, MO 63130-4899, USA dIAASARS, National Observatory of Athens, Athens, Greece

*Presenting author ([emailprotected])

Lidars are valuable instruments for vertical profiling of aerosols with the capability to remotely probe their radiative properties. Polarization-sensitive lidar systems, or polarimetric lidars, re-solve the linear depolarization ratio (LDR) of light backscattered from an illuminated volume of atmospheric constituents. The LDR is a reliable and quantitative parameter that yields infor-mation about the aerosol-particle morphology. For example, the LDR can be used to discriminate spherical and non-spherical particle shapes. Generally, the LDR values are small (<5%) for an-thropogenic aerosols such as smoke but are greater (20%) for dust, ice in clouds, or volcanic ash. The LDR values for carbonaceous soot particles, however, are less well known. These particles are created during incomplete combustion of biomass and fossil fuel (e.g., diesel and kerosene) and consist of complex aggregates of ultrafine spherical particles. Several studies have been un-dertaken to compute the LDR of soot aggregates to aid the interpretation of polarimetric lidar measurements. A major challenge with soot aggregates is that their morphology is complex and evolves with time from freshly emitted to aged smoke. Moreover, recent measurements report unexpectedly high LDR values for stratospheric smoke from a biomass-burning event. Such con-siderations motivate further modeling of how light scatters from soot, and in particular, the broadband backscattering behavior. Here, we model the broadband LDR for soot fractal aggre-gates from the ultraviolet to infrared wavelengths. Simulation results are presented based on the DDA and MSTM methods for two different fractal aggregates: chain-like aggregates and super-aggregates.

References [1] Mishchenko M. I., J. M. Dlugach, and L. Liu, 2016: Linear depolarization of lidar returns by aged

smoke particles. Appl. Opt. 55, 9968–9973.[2] Ceolato, R., et al., 2018: Lidar cross-sections of soot fractal aggregates: assessment of equivalent-

sphere models. J. Quant. Spectrosc. Radiat. Transfer 212, 39–44.[3] Haarig, M., et al., 2018: Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical

properties of aged tropospheric and stratospheric Canadian wildfire smoke. Atmos. Chem. Phys. 18,11847–11861.

Preferred mode of presentation: Oral

Characterization of aerosol optical characteristics, vertical distribution and radiative forcing of ambient aerosols over the Yangtze River Delta during 2013–2015

Huizheng Chea,*, Tianze Suna,f, Bing Qib, Yaqiang Wanga, Yunsheng Dongc,Xiangao Xiad,e, Hong Wanga, Ke Guia, Yu Zhengf, Hujia Zhaoa, Qianli Mag, Rongguang Dub, and Xiaoye Zhanga

aState Key Laboratory of Severe Weather and Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, CMA, Beijing 100081, China

bHangzhou Meteorological Bureau, Hangzhou 310051, China cKey Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics,

Chinese Academy of Science, Hefei 230031, China dLaboratory for Middle Atmosphere and Global Environment Observation, Institute of Atmospheric

Physics, Chinese Academy of Sciences, Beijing, 100029, China eSchool of Geoscience University of Chinese Academy of Science, Beijing, 100049, China fCollaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing

University of Information Science & Technology, Nanjing 210044, China gLin’ an Regional Air Background Station, Lin’ an 311307, China

*Presenting author ([emailprotected])

As the central part of eastern China, the Yangtze River Delta (YRD) region, with its rapid eco-nomic growth and industrial expansion, has experienced severe air quality issues. In this study, the monthly variation and interaction between aerosol optical properties, aerosol direct radiative forc-ing (ADRF) and aerosol vertical structure during 2013–2015 over the YRD were investigated us-ing ground-based observations from a Micro Pulse Lidar and a CE-318 sun-photometer. Combin-ing satellite products from MODIS and CALIPSO, and reanalysis wind fields, enhanced haze pol-lution events affected by different types of aerosol over the YRD region were analyzed through vertical structures, spatial distributions, backward trajectories, and the potential source contribu-tion function (PSCF) model. The results reveal that a shallower PBL coincides with higher scat-tering extinction at low altitude, resulting in less heating to the atmosphere and radiative forcing to the surface, which in turn further depresses the PBL. Like in June and September, the hygro-scopic growth facilitated by high relative humidity leads to high scattering extinction coefficient and relatively low PBL. In months with a deeper PBL, the extinction coefficient decreases rapidly with altitude, showing stronger atmospheric heating effects and ADRF to the surface by absorptive particles, facilitating the turbulence and vertical diffusion of aerosol particles, which further re-duces the extinction and raises the PBL, like July and August with high single scatter albedo (SSA). The PBL height is greater (ranging from 1.23 to 1.84 km) and more variable in the warmer months of March to August, due to the stronger diurnal cycle and exchange of heat. Not only polluted by the local emissions, northern fine-mode pollutants are brought to the YRD at a height of 1.5 km. The SSA increases, creating a feedback to the cooling effect. Originated from the deserts in Xin-jiang and Inner Mongolia, long-range transported dust masses are seen at heights of about 2 km over the YRD region with an SSA440 nm below 0.84, which heat air and raise the PBL, accelerating the diffusion of dust particles. Regional transport from biomass-burning spots to the south of the

YRD region bring absorptive particles at a height below 1.5 km, resulting in an SSA440 nm below 0.89. During the winter, the accumulation of the local emission layer is facilitated by stable weather conditions, staying within the PBL even below 0.5 km [1,2].

References [1] Sun, T., H. Che, B. Qi, et al., 2018: Aerosol optical characteristics and their vertical distributions under

enhanced haze pollution events: effect of the regional transport of different aerosol types over easternChina. Atmos. Chem. Phys. 18, 2949–2971.

[2] Sun, T., H. Che, B. Qi, et al., 2019: Characterization of vertical distribution and radiative forcing ofambient aerosol over the Yangtze River Delta during 2013–2015. Sci. Tot. Environ. 650, 1846–1857.

Preferred mode of presentation: Oral

.

Impact of aerosol non-sphericity on the satellite remote sensing of CO2

Xi Chena, Jun Wanga,*, Dongxu Yangb, Xiaoguang Xuc, Ping Yangd, Oleg Dubovike, Yi Liub, Michael Mishchenkog, and Robert Spurrh aDepartment of Chemical and Biochemical Engineering, 4133 Seamans Center, Iowa City,

IA 52242-1503, USA bInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China cJoint Center for Earth Systems Technology, University of Maryland – Baltimore County, 1000 Hilltop

Circle, Baltimore, MD 21250, USA dDepartment of Atmospheric Sciences, MS 3150, College Station, Texas 77843, USA eLaboratoire d’Optique Atmospherique, CNRS–Universite de Lille, Lille, France fInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China gNASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA hRT Solutions, Inc. Cambridge, MA 02138, USA

*Presenting author ([emailprotected])

Existing algorithms for satellite remote sensing of CO2 assume that all atmospheric aerosol parti-cles are spherical. This assumption, however, is only valid for the atmosphere in the absence of dust particles that are non-spherical by their nature. Here, a theoretical analysis is conducted for the dusty atmosphere to analyze the impact of aerosol non-sphericity on the accuracy of CO2 re-trievals from space. The analysis begins by adding new capabilities to the UNL-VRTM, a UNified and Linearized Vector Radiative Transfer Model [1] (http://unl-vrtm.org) which can calculate both the four Stokes parameters and their respective sensitivities to aerosol properties. The new capa-bility builds upon the existing non-spherical scattering property database [2,3] and develops an analytical method to calculate the Jacobians of these scattering properties to aerosol size distribu-tion parameters, index of refraction, and particle shape factors. With this new capability, the UNL-VRTM is upgraded to compute radiative transfer for the spectrum of Tan-Sat [4], and the subse-quent retrieval of CO2 [5] is conducted by using the UNL-VRTM synthetic data. In the presenta-tion, we will describe the development and validation of UNL-VRTM’s new capabilities and pro-vide an analysis of CO2 retrieval errors due to the lack of consideration of aerosol non-spherical shape in dusty conditions.

References [1] Wang, J., et al., 2014: A numerical testbed for remote sensing of aerosols, and its demonstration for

evaluating retrieval synergy from a geostationary satellite constellation of GEO-CAPE and GOES-R.J. Quant. Spectrosc. Radiat. Transfer 146, 510–528.

[2] Meng, Z., et al., 2010: Single-scattering properties of tri-axial ellipsoidal mineral dust aerosols: a data-base for application to radiative transfer calculations. J. Aerosol Sci. 41, 501–512.

[3] Dubovik, O., et al., 2002: Non-spherical aerosol retrieval method employing light scattering by sphe-roids. Geophys. Res. Lett. 29, 1415.

[4] Chen, X., et al., 2017: Angular dependence of aerosol information content in CAPI/TanSat observationover land: effect of polarization and synergy with A-train satellites. Remote Sens. Environ. 196, 163–177.

[5] Liu, Y., et al., 2018: The TanSat mission: preliminary global observations. Sci. Bull. 63, 1200–1207.

Preferred mode of presentation: Oral

Retrieval of fine-mode and coarse-mode aerosol optical properties from sun and sky radiance measurements based on aerosol type classification method

Qi-Xiang Chena, Yuan Yuana,*, and He-Ping Tanb aSchool of energy science and engineering, Harbin Institute of Technology, Harbin,150001, PR China bKey Laboratory of Aerospace Thermophysics, Ministry of Industry and Information Technology, Harbin

Institute of Technology, Harbin, 150001, PR China

*Presenting author ([emailprotected])

Aerosols are an important part of the atmosphere for it changes the radiance balance of the Earth–Ocean–Atmosphere system by absorption and scattering shortwave solar radiation and longwave earth radiation. Detailed knowledge of aerosol optical properties is needed not only to assess the aerosol climate effect but also to improve the accuracy of remote sensing. The widespread ground-based Aerosol Robotic Network (AERONET), as well as the sky radiometer network mainly lo-cated in eastern Asia (SKYNET), provides related parameters including the aerosol optical depth, complex refractive index (m), and volume size distribution (VSD) [1–3]. However, both the AER-ONET and SKYNET algorithms use the internal mixing hypothesis that assumes that fine- and coarse-mode aerosol particles have the same m values. This is not correct as the different particle modes have different compositions, and thus different m values [4,5].

In this study, we propose a new algorithm to retrieve the fine- and coarse-mode m values and VSD simultaneously by using ground-based measurements of direct sun and diffuse sky radiance. Seeing the ill-posed nature of retrieving m and VSD from scattered radiances, using a priori con-straints is critical for successfully solving such problems with many parameters. So on the basis of the previous constraints we introduce an aerosol type classification method into the retrieval process to apply specific constraints of modal m values to specific aerosol types. Numerical tests show good performance when the specific a priori constraint for different aerosol types is intro-duced compared to that a unified a priori constraint is used. Our results also suggests distinct sea-sonal variations of modal m values in typical AERONET sites.

References [1] Dubovik, O., B. Holben, T. F. Eck, et al., 2002: Variability of absorption and optical properties of key

aerosol types observed in worldwide locations. J. Atmos. Sci. 59, 590–608.[2] Dubovik, O., and M. D. King, 2000: A flexible inversion algorithm for retrieval of aerosol optical

properties from sun and sky radiance measurements. J. Geophys. Res. 105, 20673–20696.[3] Nakajima, T., G. Tonna, R. Z. Rao, et al., 1996: Use of sky brightness measurements from ground for

remote sensing of particulate polydispersions. Appl. Opt. 35, 2672–2686.[4] Xu, X. G., and J. Wang, 2015: Retrieval of aerosol microphysical properties from aeronet photopolarimetric

measurements. 1. Information content analysis. J. Geophys. Res. Atmos. 120, 7059–7078.[5] Xu, X. G., J. Wang, J. Zeng, et al., 2015: Retrieval of aerosol microphysical properties from aeronet

photopolarimetric measurements. 2. A new research algorithm and case demonstration. J. Geophys.Res. Atmos. 120, 7079–7098.

Preferred mode of presentation: Poster

An inverse scattering problem for 2-D dielectrics via Eikonal approximation

Charles E. Chika

The University of Texas at Dallas, 800 W Campbell Rd., Richardson, TX 75080, USA ([emailprotected])

A non-iterative method for constructing a class of 2-dimensional (2-D) refractive index of a me-dium from forward scattering amplitude data of electromagnetic plane waves incident at different angles and frequencies was developed. The 2-D Eikonal approximation of the scattering amplitude was derived by considering the integral representation of the solution of the Helmoholz equation, and then it is used to develop an inverse method to construct the 2-D refractive index. Also, nu-merical comparisons were carried out for the refractive index constructed from the Eikonal ampli-tude using the inverse method developed with the one constructed from the exact amplitude as well as the exact refractive index for some known examples. This inverse method will be effective in applications because it is easy to implement and gives good recovery (or construction) of re-fractive index [1].

In this presentation, we summarize our result, its limitations, advantages and future works.

References [1] Chika, C. E., and M. A. Hooshyar, 2019: An electromagnetic inverse scattering problem for dielectrics

that depend on two spatial variables via Eikonal approximation. Microw. Opt. Technol. Lett.,https://doi.org/10.1002/mop.31752.

Preferred mode of presentation: Oral

Measurements of light extinction by single aerosol particle elevated by linear electrodynamic quadrupole

Fenghong Chua,*, Allen Haddrellb, Antonio Valenzuelab, Jim S. Walkerb,Andrew J. Orr‐Ewingb, and Jonathan Reidb

aShanghai University of Electric Power, 2103 Pingliang Road, Shanghai, 200090, China bSchool of Chemistry, University of Bristol, BS8 1TS, UK

*Presenting author ([emailprotected])

A new experiment is presented for the measurement of single aerosol particle optical cross section combining laser-based cavity ring-down spectroscopy (CRDS) with a linear electrodynamic quad-rupole (LEQ) ion trap in tandem with phase function measurements. The LEQ utilizes the quad-rupole field created by four parallel rods spaced in a square pattern with an AC voltage applied to pairs of diametrically opposing rods. The time-varying field constrains charged particles to a point in the two-dimensional plane perpendicular to the rod axes, producing a line of stability along the geometric center [1]. This approach allows direct measurements of the changing optical cross sec-tions of individual aerosol particles over indefinite time-frames facilitating some of the most com-prehensive measurements of the optical properties of aerosol particles so far made.

The variation in ringdown time with the position of 1,2,6-hexanetriol particle within the CRD beam is measured. The particle can not only be translated vertically along the z axis by varying DC voltage at the bottom and air flow rate from the top of quadrupole but also along the x-y axis by translating the position of the quadrupole. The measurements illustrate the sensitivity in the ringdown time to the position of the particle within the Gaussian waist of the CRD beam, with the largest reduction observed only when the particle is carefully aligned to the center of the TEM00 mode profile. The radius of 1,2,6-hexanetriol particle at 532 nm is determined from PFs and optical cross section at 405nm is measured over a continuous radius range.

This facility can be also used to measure the optical properties of absorbing aerosols, including brown carbon particulates. These tiny particles affect both the optical properties and the tempera-ture of the Earth’s atmosphere. For example, brown carbon absorbs sunlight, can affect the warm-ing of the atmosphere by solar radiation, and can reduce visibility in polluted environments [2–4].

References [1] Hart, M. B., V. Sivaprakasam, J. D. Eversole, et al., 2015: Optical measurements from single levitated

particles using a linear electrodynamic quadrupole trap. Appl. Opt. 54, 174–181.[2] Andreae, M.O., and A. Gelenser, 2006: Black carbon or brown carbon? The nature of light-absorbing

carbonaceous aerosols. Atmos. Chem. Phys. 6, 3131–3148.[3] Alexander, D. T. L., P. A. Crozier, and J. R. Anderson, 2008: Brown carbon spheres in East Asian

outflow and their optical properties. Science 321, 833–836.[4] Feng, Y., V. Ramanathan, and V. R. Kotamarthi, 2013: Brown carbon: a significant atmospheric ab-

sorber of solar radiation? Atmos. Chem. Phys. 13, 8607–8621.

Preferred mode of presentation: Poster

Using Pattern Equation Method for solving the problem of EM scattering by thin dielectric cylinder

Dmitri B. Demina, Andrey I. Kleevb, and Alexander G. Kyurkchana,c,d,*

aMoscow Technical University of Communications and Informatics, 8а Aviamotornaya str., Moscow111024, Russian Federation

bP. L. Kapitsa Institute for Physical Problems, Russian Academy of Sciences, 2 Kosygina str., Moscow 119334, Russian Federation

cKotel’nikov Institute of Radio Engineering and Electronics, Fryazino Branch, Russian Academy of Sci-ences, pl. Vvedenskogo 1, Fryazino, Moscow oblast, 141190, Russian Federation

dCentral Research Institute of Communication, 8 1st Perova Polya Drive, Moscow 111141, Russian Federation

*Presenting author ([emailprotected])

At present, the Rayleigh approximation [1] is almost the only mathematical model used in solv-ing the problem of scattering on small bodies. In the well-known monographs [1–3], this approach is described in sufficient detail especially for the cases when the solution of an auxiliary electro-static problem can be obtained in an explicit form. In this paper, an alternative method is devel-oped based on the Pattern Equation Method (PEM) [4–6]. When constructing a new approach to the analysis of scattering on small bodies, we used the high convergence of the PEM established in the above papers. Indeed, as shown by the calculations, to solve the problem of scattering on bodies whose characteristic size is comparable to the wavelength of the scattering field, it is suffi-cient to take into account, depending on the polarization of the incident field, from one to three terms in the expansion of the scattering pattern. This circ*mstance made it possible to obtain ex-plicit formulas for the integral scattering characteristics applicable to scatterers of a complex shape.

References [1] van de Hulst, H. C., 1957: Light Scattering by Small Particles. Wiley, New York.[2] Bohren, C. F., and D. R. Huffman, 1983: Absorption and Scattering of Light by Small Particles. Wiley,

New York.[3] Mishchenko, M. I., J. W. Hovenier, and L. D. Travis L.D., 2000: Light Scattering by Nonspherical

Particles. Academic Press, San Diego.[4] Kyurkchan, A. G., and N. I. Smirnova, 2016: Mathematical Modeling in Diffraction Theory Based on

A Priori Information on the Analytic Properties of the Solution. Elsevier, Amsterdam.[5] Demin, D. B., A. I. Kleev, and A. G. Kyurkchan, 2017: Modeling of electromagnetic scattering by thin

cylinders using Pattern Equation Method. J. Quant. Spectrosc. Radiat. Transfer 187, 287–292.[6] Demin, D. B., A. I. Kleev, and A. G. Kyurkchan, 2018: Application of the Pattern Equation Method to

the analysis of electromagnetic wave scattering by a thin cylinder of an arbitrary cross section. J. Com-mun. Technol. Electron. 63, 505–511.

Preferred mode of presentation: Poster

Analysis of a scattering by a cylinder of a large cross section using the Hybrid Pattern Equations Method

Dmitri B. Demina, Andrey I. Kleevb, and Alexander G. Kyurkchana,c,d,*

aMoscow Technical University of Communications and Informatics, 8а Aviamotornaya str., Moscow111024, Russian Federation

bP. L. Kapitsa Institute for Physical Problems, Russian Academy of Sciences, 2 Kosygina str., Moscow 119334, Russian Federation

cKotel’nikov Institute of Radio Engineering and Electronics, Fryazino Branch, Russian Academy of Sci-ences, pl. Vvedenskogo 1, Fryazino, Moscow oblast, 141190, Russian Federation

dCentral Research Institute of Communication, 8 1st Perova Polya Drive, Moscow 111141, Russian Federation

*Presenting author ([emailprotected])

Scattering of waves by obstacles whose dimensions substantially exceed the wavelength of the incident radiation is one of the key problems in the theory of diffraction. In the present paper we propose a new methodology based on the Pattern Equations Method (PEM) [1,2]. The high rate of convergence of the PEM established in the above studies can be used to construct various asymp-totic approaches. In particular, using PEM, the authors succeeded in obtaining approximate for-mulas for the integral cross section for scattering by Rayleigh objects [3]. In this paper, we develop a Hybrid Pattern Equations Method (HPEM), based on the use of a combination of PEM and the Physical Optics approximation (PO). The integral–differential equation for the “correction” to the PO solution for the scattering pattern is obtained. It is shown that this approach has a high effi-ciency and, at the same time, does not require significant computational costs in solving diffraction problems for cylinders, even in cases where the characteristic cross-sectional dimension is large compared to the wavelength of the incident radiation. The rate of convergence, as well as the accuracy of the results obtained, depend weakly on the geometric dimensions of the cross section of the cylinder, which makes this approach a promising method for calculating the scattering char-acteristics in those cases when the transverse dimension of the scatterer substantially exceeds the wavelength of the incident field.

References [1] Kyurkchan, A. G., and N. I. Smirnova, 2016: Mathematical Modeling in Diffraction Theory Based on

A Priori Information on the Analytic Properties of the Solution. Elsevier, Amsterdam.[2] Demin, D. B., A. I. Kleev, and A. G. Kyurkchan, 2017: Modeling of electromagnetic scattering by thin

cylinders using Pattern Equation Method. J. Quant. Spectrosc. Radiat. Transfer 187, 287–292.[3] Demin, D. B., A. I. Kleev, and A. G. Kyurkchan, 2018: Application of the Pattern Equation Method to

the analysis of electromagnetic wave scattering by a thin cylinder of an arbitrary cross section. J. Com-mun. Technol. Electron. 63, 505–511.

Preferred mode of presentation: Poster

Bio-inspired structures for radiative cooling applications

Azadeh Didaria and M. Pinar Mengüçb,* aDepartment of Electrical and Electronics Engineering, Istanbul Şehir University, 34865 Istanbul, Turkey bCenter for Energy, Environment and Economy (CEEE), Ozyegin University, Istanbul 34794, Turkey

*Presenting author ([emailprotected])

Blue Peruvian Morpho didius butterfly is a special butterfly species that shows a magnificent iri-descent blue color in its wings. This iridescent structural color which plays a dominant role in the overall glossy blue color of the wings has been evolved for survival and recognizability purposes over the years. Earlier investigations of the wing structures had shown that these butterflies have pheromone-producing organs which act as a thermal regulator system within their wings [1]. In-spired by the micro and nanostructures of their wings, in this work, we present a biomimetic model based on the Morpho didius butterfly wings which shows potential to be utilized in radiative cool-ing applications. This biomimicry design involves SiC palm tree-like structures placed in nano-scale separation of a thin film in a vacuum environment. The near-field energy exchange is en-hanced significantly by decreasing the dimensions of the tree and rotating the free-standing tree structure by 90 degrees clockwise and also by decreasing the separation distance with the second thin film. This exchange is calculated by using near-field radiative transfer finite difference time domain algorithm [2]. Several orders of enhancement of near-field heat flux within the infrared atmospheric window (8–13 μm bandwidth) are achieved [3]. This spectrally selective enhance-ment is due to the geometric variations, the spatial location of the source of excitation and the optical properties of the materials, and can be tuned to tailor strong radiative cooling mechanisms.

References [1] Tsai, C.-C., N. N. Shi, C. Ren, J. Pelaez, G. D. Bernard, N. Yu, and N. Pierce, 1917: Butterflies regulate

wing temperatures using radiative cooling. Proc. SPIE 10367, 10367OA.[2] Didari, A., and M. P. Mengüç, 2017: A design tool for direct and non-stochastic calculations of near-

field radiative transfer in complex structures: the NF-RT-FDTD algorithm. J. Quant. Spectrosc. Radiat.Transfer 197, 95–105.

[3] Didari, A., and M. P. Mengüç, 2018: A biomimicry design for nanoscale radiative cooling applicationsinspired by Morpho didius butterfly. Sci. Rep. 8, 16891.

Preferred mode of presentation: Oral

Multiple scattering of polarized light by particles in an absorbing host medium

Janna M. Dlugacha,* and Michael I. Mishchenkoa aMain Astronomical Observatory of the National Academy of Sciences of Ukraine, 27 Zabolotny Str.,

03680, Kyiv, Ukraine bNASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA

*Presenting author ([emailprotected])

We use recently developed first-principles tools [1–3] to solve the vector radiative transfer equa-tion for a particulate layer imbedded in an absorbing host medium. The results of extensive com-putations for typical geophysical scenarios are analyzed, and conclusions are formulated as to the practical importance of the effects of absorption in the host medium.

References [1] Mishchenko, M. I., 2008: Multiple scattering by particles embedded in an absorbing medium. 2. Radi-

ative transfer equation. J. Quant. Spectrosc. Radiat. Transfer 109, 2386–2390.[2] Mishchenko, M. I., and P. Yang, 2018: Far-field Lorenz–Mie scattering in an absorbing host medium:

theoretical formalism and FORTRAN program. J. Quant. Spectrosc. Radiat. Transfer 205, 241–252.[3] Mishchenko, M. I., J. M. Dlugach, J. A. Lock, and M. A. Yurkin, 2018: Far-field Lorenz–Mie scattering

in an absorbing host medium. II: Improved stability of the numerical algorithm. J. Quant. Spectrosc.Radiat. Transfer 217, 274–277.

Preferred mode of presentation: Oral

On the order of atmospheric scattering, its polarization and computation efficiency

Minzheng Duan

LAGEO, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China ([emailprotected])

Polarization becomes more and more important in current and future remote sensing of earth’s atmosphere and astronomical observations, as it could provide more information than that of in-tensity-only measurements. While forward simulation of polarization of light during its transfer in the earth-atmosphere system is still a burden especially for the full polarized radiative transfer with heavy aerosol loading. Based on previously established model-SOSVRT, a full polarized radiative transfer model with successive order of scattering method, the polarization of atmospheric scatter-ing under different aerosol loadings are simulated, the lights for each scattering order, its polari-zation and the errors introduced by ignoring the polarization are analyzed. We are trying to answer how many orders are necessary in polarization simulations. Finally, a new method to speed up the modelling of polarized radiative transfer is proposed.

Preferred mode of presentation: Poster

Extension of vectorial complex ray model to 3D light scattering by large non-spherical particles

Qingwei Duana,b, Xiang’e Hana, and Kuan Fang Renb* aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCORIA-UMR 6614-Normandie Universite, CNRS-Universite et INSA de Rouen, Campus Universitaire

du Madrillet, 76 800 Saint-Etienne du Rouvray, France

*Presenting author ([emailprotected])

The calculation for the 3D light scattering of large particle with irregular shape is still a challenging problem because of its complexity. The available numerical methods such as T matrix, discrete multipole approximation, etc., are severely limited by the size parameter of the scatter [1]. The geometric optics approximation method, be flexible as claimed, has made little headway for 3D light scattering due to its inherent drawbacks. And the variable separation methods such as Lorenz-Mie theory and Debye series expansion are limited to objects with regular shapes such as spheres, ellipsoids and cylinders. Ren et al. in [2] proposed the vectorial complex ray model (VCRM), aiming to solve the light scattering by large non-spherical particles. However, the current numeri-cal implementation of the VCRM only addresses rays propagating within a 2D plane [3].

In this paper, we firstly propose the extension of VCRM to the 3D light scattering by large particles of irregular shapes. The proposed method is very flexible and can be applied, theoreti-cally, to solving the 3D light scattering by any large particle, as long as the particle has a smooth surface. Another significant advantage is its efficiency. For a non-spherical particle with size pa-rameter over 5000, the time needed to calculate the 3D scattering field only takes about 20 minutes on a laptop, without parallel computation. An application of the method to the 3D light scattering by a circular liquid jet [4–6] with irregular geometry is given to show its capability, and the simu-lation result agrees well with that by experiment.

3D Light scattering by a circular liquid jet with size parameter being about 5000 and surface being com-plex. Left: propagation directions of scattering rays for different times of interaction. Right: comparison of the scattering field near the 2nd rainbow by simulation (in red) with that by experiment (in hot map).

References [1] Mishchenko, M. I., J. W. Hovenier, and L. D. Travis, 2000: Light Scattering by Nonspherical Particles:

Theory, Measurements, and Applications. Academic Press, San Diego.[2] Ren, K. F., F. R. A. Onofri, C. Rozé, and T. Girasole, 2011: Vectorial complex ray model and applica-

tion to two-dimensional scattering of plane wave by a spheroidal particle. Opt. Lett. 36, 370–372.[3] Onofri, F. R. A., K. F. Ren, M. Sentis, et al., 2015: Experimental validation of the vectorial complex

ray model on the inter-caustics scattering of oblate droplets. Opt. Express 23, 15768.[4] Han, X., K. F. Ren, Z. Wu, F. Corbin, G. Gouesbet, and G. Gréhan, 1998: Characterization of initial

disturbances in a liquid jet by rainbow sizing. Appl. Opt. 37, 8498–8503.[5] Ambravaneswaran, B., H. J. Subramani, et al., 2004: Dripping–jetting transitions in a dripping faucet.

Phys. Rev. Lett. 93, 034501.[6] Duan, Q., R. Zhong, X. Han, and K. F. Ren, 2017: Influence of spatial curvature of a liquid jet on the

rainbow positions: ray tracing and experimental study. J. Quant. Spectrosc. Radiat. Transfer 195, 156–163.

Preferred mode of presentation: Oral

Retrievals of aerosol properties using an AERONET tuned implementation of the Dark Target and GRASP inversion frameworks

W. Reed Espinosaa,*, Robert C. Levya, Oleg Dubovikb, Yingxi R. Shia,c,Lorraine A. Remerd, Tatyana Lapyonokb, and David Fuertese

aGoddard Space Flight Center, Greenbelt, MD, USA bLaboratoire d’Optique Atmospherique, UMR8518, CNRS – Universite de Lille 1, Villeneuve d’Ascq,

France cGESTAR, Universities Space Research Association, Columbia, MD, USA dJoint Center for Earth Systems Technology, Baltimore, MD, USA eGRASP-SAS, Remote sensing developments, Universite des Sciences et Technologies de Lille, Villeneuve

d’Ascq, France

*Presenting author ([emailprotected])

In this work we combine novel and well-established retrieval techniques to obtain improved esti-mates of aerosol optical depth (AOD) over land and ocean from observations made by the Moder-ate Resolution Imaging Spectroradiometer (MODIS). The radiances used as retrieval inputs are obtained using the gas absorption corrections as well as the pixel screening and aggregation tech-niques of the well-established Dark Target algorithm. The long heritage of these techniques pro-vides confidence that the resulting radiances are predominantly free from artifacts that can nega-tively influence retrievals, including cloud contamination, suspended sediment and sun glint. These preprocessed radiances are then fed into the advanced and highly flexible Generalized Re-trieval of Aerosol and Surface Properties (GRASP) algorithm. The versatility of the GRASP in-version framework allows for a set of customized assumptions regarding the surface and intensive aerosol properties. In order to derive a set of assumptions that ultimately best utilizes the limited information content of the MODIS measurement, we make use of the flexibility of the GRASP code and first perform a synergistic joint retrieval on both the MODIS radiances and collocated AOD measurements made by AERONET sun photometers. The resulting retrievals of surface properties as well as aerosol concentration, size, refractive index and shape are then used to con-strain a retrieval exclusively utilizing MODIS observations in a manner that is consistent with both the MODIS measurement and the highly accurate AERONET AOD. The tuned MODIS retrieval was then applied to all pixels collocated with 120 globally representative AERONET sites over a 15-year period. Over ocean, the results indicate that at 550 nm the new retrieval was highly corre-lated with the AERONET AOD’s (R = 0.900). Furthermore, the net AOD biases of the new methodwere consistently below 0.01 across all six retrieved wavelengths, significantly less than the cor-responding Dart Target biases of 0.02–0.05. Furthermore, the RMS errors were reduced relativeto the standard Dark Target algorithm, with 7% more retrievals falling within the World Metro-logical Organization’s target AOD accuracy range of Δτ = ±0.03 ±0.1τ.

Preferred mode of presentation: Oral

Internal and near-surface fields of a charged sphere illuminated by a vector Bessel beam

Yinan Fenga,†, Yiming Yanga, and Renxian Lia,b,*

aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University,

Xi’an 710071, China

†Presenting author ([emailprotected]) *Corresponding author ([emailprotected])

Vector vortex beams (VVBs) [1] have recently attracted increasing interest for various applications including super-resolution imaging, on-chip switching, optical tweezers [2], and so on. It is worth mentioning that a VVB may carry both phase singularity and polarization singularity. Many re-searchers have studied the singularities (optical vortices) carried by VVBs, and a new branch of physics name singular optics [3,4] is formed. Most the applications involve the interaction of VVBs with particles, which can be rigorously solved using generalized Lorenz–Mie theory [5]. However, it gives few clues to the various physical processes that are responsible for the scattering. To isolate the contribution of various scattering process and to further investigate the physical origins of many effects that occur in scattering, the internal and scattering coefficients can be re-written in terms of Debye series expansion (DSE) [6–9].

The aim of this paper is to discuss the internal and near-surface fields of a charged sphere illuminated by a vector Bessel beam using DSE. The internal and scattered coefficients for a charged sphere are first expanded using DSE, and the beam shape coefficients (BSCs) of a VVB are derived using the angular spectrum decomposition and the multipole expansion of spherical harmonic functions. The internal and near-surface fields of a charged sphere illuminated by a VVB are numerically computed. The effects of the carried charges, the order, polarization, and half-cone angle of the beams are discussed. The internal fields for various scattering processes (namely De-bye mode p) are analyzed. Potential applications of these results include particle sizing, optical trapping and manipulation, etc.

References [1] Gong, S., R. Li, Y. Liu, et al. 2018: Scattering of a vector Bessel vortex beam by a charged sphere.

J. Quant. Spectrosc. Radiat. Transfer 215, 13–24.[2] Mitri, F. G., T. P. Lobo, G. T. Silva, 2012: Axial acoustic radiation torque of a Bessel vortex beam

on spherical shells. Phys. Rev. E 85, 026602.[3] Šiler, M., and P. Zemanek 2013: Optical forces in a non-diffracting vortex beam. J. Quant. Spectrosc.

Radiat. Transfer 126, 78–83.[4] Mitri, F. G., R. X. Li, L. X. Guo, et al., 2017: Optical tractor Bessel polarized beams. J. Quant.

Spectrosc. Radiat. Transfer 187, 97–115.[5] Gouesbet, G., and G. Gréhan, 2011: Generalized Lorenz–Mie theories. Springer, Berlin.[6] Laven, P., 2004: Simulation of rainbows, coronas and glories using Mie theory and the Debye

series. J. Quant. Spectrosc. Radiat. Transfer 89, 257–269.

[7] Hovenac, E. A., and J. A. Lock, 1992: Assessing the contributions of surface waves and complexrays to far-field Mie scattering by use of the Debye series. J. Opt. Soc. Am. A 9, 781–795.

[8] Li, R., X. Han, and K. F. Ren, 2010: Debye series analysis of radiation pressure force exerted ona multilayered sphere. Appl. Opt. 49, 955–963.

[9] Li, R., X. Han, L. Shi et al., 2007: Debye series for Gaussian beam scattering by a multilayeredsphere. Appl. Opt. 46, 4804–4812.

Preferred mode of presentation: Oral

Monte Carlo code and modelling of polarized radiative transfer in the envelopes of post-AGB objects

Juris Freimanis* and Romāns Peženkovs

Engineering Research Institute “Ventspils International Radio Astronomy Centre” of Ventspils University College, 101 Inženieru iela, Ventspils, LV-3600, Latvia

*Presenting author ([emailprotected])

It is widely believed that post-asymptotic giant branch (post-AGB) objects are undergoing a transition phase from a “normal” star burning its nuclear fuel to a planetary nebula [1]. Their progenitors are stars with the main sequence mass in the range from (very approximately) 2 to 8 solar masses. They have extended gas–dust envelopes of various (often very peculiar, and often bipolar) shapes created by an intense mass loss. This is an important stage in star’s life; the mass outflow substantially enriches the interstellar medium with heavy elements, driving the chemical evolution of the host galaxy. The asymmetric shape of an outflow from an initially almost spher-ically symmetric star is not fully explained, but extensive research of this topic is being done worldwide. The binary nature of a star has been proposed as the cause of bipolar outflows, and moreover it has been supposed that some post-AGBs never become planetary nebulae [2].

In recent years, new powerful astronomical instruments have started to provide spatially re-solved polarized images of these objects [3,4] as well as high-resolution interferometric data [5]. In order to make conclusions about the morphology and spatial distribution of matter in optically thick circ*mstellar envelopes as well as about the chemical composition, size, shape and orienta-tion of dust grains, polarized radiative transfer modelling must be performed.

We have created a Monte Carlo computer code for the modelling of polarized continuum ra-diative transfer in an arbitrarily shaped circ*mstellar dust cloud. The scattering medium is discre-tized into rectangular parallelepipeds; the properties of individual dust grains are assumed to be constant inside each parallelepiped, but the concentration of the grains may vary smoothly. The first version of our code assumes a macroscopically isotropic and mirror-symmetric scattering medium [6], but we are working to relax this assumption. The program has been written in the C++ language, and the calculations are done on our computing cluster using one of its nodes with 16 cores.

Our first attempts to interpret really observed post-AGB objects are in progress. Our code can be used for the interpretation of other astronomical objects as well provided that (i) general relativistic effects are not essential, (ii) birefringence is negligible, and (iii) refraction can be ne-glected, i.e., radiation propagates along straight lines between the successive acts of scattering.

References [1] Gail, H.-P., and Sedlmayr, E., 2014: Physics and Chemistry of Circ*mstellar Dust Shells. Cambridge

University Press, New York.[2] Lagadec, E., 2017: Post-AGB nebular studies. Proc. Int. Astron. Union 12 (S323), 20–27.[3] Lagadec, E., 2018: AGBs, post-AGBs and the shaping of planetary nebulae. Galaxies 6, 99 – 106.[4] Sahai, R., D. C. Hines, J. H. Kastner, et al., 1998: The structure of the prototype bipolar planetary

nebula CRL 2688 (Egg Nebula): broadband, polarimetric, and H2 line imaging with NICMOS on the

Hubble Space Telescope. Astrophys. J. 492, L163–L167. [5] Paladini, C., F. Baron, A. Jorissen, et al., 2017: Large granulation cells on the surface of the giant star

π1 Gruis. Nature 553, 310–312.[6] Mishchenko, M. I., L. D. Travis, and A. A. Lacis, 2002: Scattering, Absorption, and Emission of

Light by Small Particles. Cambridge University Press, Cambridge, UK.

Preferred mode of presentation: Oral

Joint retrieval of aerosol properties and water leaving radiance using multi-angular polarimetric measurements over open and coastal ocean waters Meng Gaoa*, Peng-Wang Zhaib, Bryan Franzc, Yongxiang Hud, Kirk D. Knobelspiessec, Jeremy Werdellc, Amir Ibrahima , Brian Cairnse, and Alison Chasef

aSSAI, NASA Goddard Space Flight Center, Code 616, Greenbelt, Maryland 20771, USA bJCET/Physics Department, University of Maryland, Baltimore County, Maryland, 21250, USA cNASA Goddard Space Flight Center, Code 616, Greenbelt, Maryland 20771, USA dNASA Langley Research Center, Hampton, VA 23668 eNASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA f School of Marine Sciences, University of Maine, Orono, ME 04469, USA *Presenting author ([emailprotected]) Ocean color remote sensing is a challenging task over coastal waters due to the complex optical properties of aerosols and hydrosols. In order to accurately estimate water leaving signals, we implemented a joint retrieval algorithm to obtain aerosol properties and water leaving signal simultaneously based on polarimetric measurements. The algorithm can be applied to both open and coastal waters. The open water optical properties in the algorithm are modeled by the chlorophyll-a concentration, while the coastal water optical properties are modeled by seven parameters which explicitly account for the absorption and scattering by phytoplankton, colored dissolved organic matter and non-algal particles. The aerosol and ocean optical properties are retrieved by the Levenberg–Marquardt optimization algorithm based on a coupled atmosphere and ocean radiative transfer model. The algorithm has been validated with synthetic data generated by a vector radiative transfer model [1]. We will discuss the retrieval procedure and accuracy using the airborne Research Scanning Polarimeter measurements from two field campaigns [2]. The goal is to assist the future development of the atmospheric correction algorithm using polarimetric measurements for the NASA’s Plankton, Aerosol, Cloud, and ocean Ecosystem mission, which includes a hyperspectral Ocean Color Instrument and two multi-angle polarimeters onboard: the UMBC Hyper Angular Rainbow Polarimeter and the SRON Spectro-polarimeter for Planetary EXploration. References [1] Gao, M., P.-W. Zhai, B. Franz, Y. Hu, K. Knobelspiesse, P. J. Werdell, A. Ibrahim, F. Xu, and B.

Cairns, 2018: Retrieval of aerosol properties and water-leaving reflectance from multi-angular polarimetric measurements over coastal waters. Opt. Express 26, 8968–8989.

[2] Gao, M., P.-W. Zhai, B. Franz, Y. Hu, K. Knobelspiesse, P. J. Werdell, A. Ibrahim, B. Cairns, and A. Chase, 2019: Inversion of multi-angular polarimetric measurements over open and coastal ocean waters: a joint retrieval algorithm for aerosol and water leaving radiance properties. Atmos. Meas. Tech., submitted.

Preferred mode of presentation: Oral

A numerical study about optical trapping properties of nanoparticle on composite metallic film Cheng-Xian Gea, Zhen-Sen Wua,*, Jing Baia, and Lei Gongb

aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an, Shaanxi, 710071, China bSchool of Photoelectric Engineering, Xi’an Technological University, Xi’an, Shaanxi, 710021, China *Presenting author ([emailprotected], [emailprotected]) In recent years, optical trapping and manipulation of particles have been widely used in different areas of science particularly in researching the optical trapping properties of surface plasmon polaritons due to the advantages of being high precision and sensitivity [1], since the pioneering work of Ashkin et al. on trapping a dielectric microsphere using a single focused laser beam. Nowadays it has been applied to manipulate nanoparticle near the composite metallic film with periodic structure.

Based on the three-dimensional dispersive finite difference time domain method and Maxwell stress tensor equation, the optical trapping properties of nanoparticle placed on the composite metallic film are investigated numerically. Surface plasmon polaritons are excited on the metal-dielectric interface with particular emphasis on the crucial role in tailoring the optical force acting on a nearby nanoparticle. In order to obtain the detailed trapping properties of nanoparticle, selected calculations on the effects of beam waist radius, sizes of nanoparticle and circular holes, distance between incident Gaussian beam and composite metallic film, material of nanoparticle and polarization angles of incident wave are analyzed in detail to demonstrate that the optical trapping force can be interpreted as a virtual spring which has a restoring force to perform positive and negative forces as nanoparticle moving closer to or away from the centers of periodic structure. The results could provide guidelines for further research on the optical system design and manipulation of arbitrary composite nanoparticles.

Fig. 1. Schematic of the target placed on the composite metallic film with periodic structure.

In this paper, the effects of various parameters on the composite model are investigated in detail to obtain the analytical results. Figure 1 shows the main schematic of the research. The meaning of the parameters will be discussed in our future work.

Silicon

dioxide

Silicon dioxide

Silicon dioxide

Gold film Gold film

Exploded diagram

Structure diagram

Variable parameters of the composite

structure

X

Y

Z

Circular holes

0w Gaussian Wave

Ly

Lx

d

Lc

Lb

La

Target

mailto:[emailprotected]

mailto:[emailprotected]

Reference [1] Ashkin, A., J. M. Dziedzic, J. E. Bjorkholm, and S. Chu, 1986: Opt. Lett. 11, 288.

Light scattering by dust particles in the innermost coma of comet 67P/Churyumov–Gerasimenko: synthetic images from numerical simulations in comparison with Rosetta OSIRIS data

Selina-Barbara Geriga,*, Raphael Marschallb, Olga J. Pinzón Rodrigueza, Nicolas Thomasa, and the OSIRIS team aPhysikalisches Institut, Sidlerstrasse 5, University of Bern, CH-3012 Bern, Switzerland bInternational Space Science Institute (ISSI), Hallerstrasse 6, CH-3012 Bern, Switzerland

*Presenting author ([emailprotected])

During two years, from August 2014 – September 2016, ESA’s Rosetta spacecraft followed comet 67P/Churyumov–Gerasimenko (hereafter 67P) along its orbit and collected a vast amount of data about both the nucleus and the innermost coma with a large set of scientific instruments.

Dust in the innermost coma of 67P is visible through sunlight scattered by dust particles, which was caught on the images of Rosetta’s scientific Optical, Spectroscopic, and Infrared Remote Im-aging System (OSIRIS) cameras [1]. The dust in the innermost coma is dragged away from the surface by outgassing from sublimating ices on the nucleus and the motion of the dust is coupled, although in a complex way, to the motion of the gas. The OSIRIS image data set offers therefore the unique opportunity to study global gas and dust dynamics and dust grain properties in the innermost coma of comet 67P through sunlight scattered in the coma itself. However, the inverse problem of determining the properties of scattering particles just by the field of scattered light is extremely challenging and complicated to solve unambiguously. Our approach is to numerically model the gas and dust dynamics in the coma around the comet in full 3D and then apply a Mie scattering model to produce synthetic images that can be directly compared to the original data from OSIRIS observations [2]. In our computer model we simulate the dynamic behaviour of 40 discrete dust size bins and weight our results according to a power law function of the type n(rd) ~ rd–b, with n being the number density, rd the radius of the dust particles and b the power law exponent determining the steepness of the particle size distribution. Our simulated dust sizes range between rd = 8 nm – 0.3 mm corresponding to size parameters of 0.08 < x < 3265 (x = 2πrd/λ, with λ being the wavelength of the incident light). This method allows us to test different combinations of input parameters, governing for example the particle size distribution, to determine the most probable set of parameters that best describe the observations.

To study the dynamical behaviour of gas and dust in the innermost coma of 67P we analyse azimuthally averaged pixel column brightnesses with increasing distance from the nucleus, the so-called “azimuthal average profiles” [3]. The column brightness from scattered light by dust parti-cles in the coma is proportional to the integrated number density along the camera line-of-sight for an optically thin coma. Deviations of real data results from simplified model predictions of dust number densities are therefore a direct sign for additional physical processes engaged in the dy-namical behaviour of gas and dust not accounted for in the model and hence an interesting field of research.

In our recent studies we have focused on the possibility to explain deviations from simulation results to OSIRIS data especially prominent on the night side of the coma with the presence of

large particles. Large particles can be captured in gravitationally bound orbits or on long ballistic trajectories around the nucleus and have been observed in the vicinity of 67P (e.g., [4]). Here we explore how to incorporate large particle scattering in our model and study its effects on the azi-muthal average profile in combination with the simulated main bulk of the dust coma that is scat-tering sunlight in the Mie regime.

In this talk we will portray how we use numerical simulation of gas and dust dynamics com-bined with a Mie particle scattering model to calculate synthetic images in spectral radiance which can be compared directly to OSIRIS images. We will also shortly discuss our latest results regard-ing the deviations between simulated data and observations and explain our findings and the im-plications thereof.

The team from the University of Bern is supported through the Swiss National Science Foun-dation and through the NCCR PlanetS.

OSIRIS was built by a consortium of the Max-Planck-Institut für Sonnensystemforschung, Goettingen, Germany; CISAS–University of Padova, Italy, the Laboratoire d’Astrophysique de Marseille, France; the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain; the Research and Scientific Support Department of the European Space Agency, Noordwijk, The Netherlands; the Instituto Nacional de Tecnica Aeroespacial, Madrid, Spain; the Universidad Politechnica de Madrid, Spain; the Department of Physics and Astronomy of Uppsala University, Sweden; and the Institut fuer Datentechnik und Kommunikationsnetze der Technischen Universitaet Braun-schweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is grate-fully acknowledged.

References [1] Keller, H. U., et al., 2007: OSIRIS – the scientific camera system onboard Rosetta. Space Sci. Rev. 128,

433–506.[2] Marschall, R., et al., 2016: Modelling observations of the inner gas and dust coma of comet 67P/Chur-

yumov–Gerasimenko using ROSINA/COPS and OSIRIS data: first results. Astron. Astrophys. 589,A90.

[3] Gerig, S.-B., et al., 2018: On deviations from free-radial outflow in the inner coma of comet 67P/Chur-yumov–Gerasimenko. Icarus 311, 1–22.

[4] Rotundi, A., et al., 2015: Dust measurements in the coma of comet 67P/Churyumov–Gerasimenkoinbound to the Sun. Science 347, aaa3905.

Preferred mode of presentation: Oral

Scattering of Bessel beams in the framework of the discrete dipole approximation

Stefania A. Gluhovaa,b,* and Maxim A. Yurkina,b

aVoevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia

bNovosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia

*Presenting author ([emailprotected])

In recent years Bessel beams have been gaining special popularity [1]. They belong to the class of non-diffraction beams which do not spread out during propagation (like an unbounded plane wave). Despite the fact that the ideal Bessel beam cannot be obtained in the experiment due to finite energy, it is often sufficient to have an approximate Bessel beam in a finite domain. While the scattering of these beams by particles of simple shapes, such as spheres, has been discussed in the literature, it is rarely considered for complex particles.

The discrete dipole approximation (DDA) is a popular method to simulate scattering and absorption of electromagnetic waves by particles of arbitrary shape and internal structure. In this method the volume of the scatterer is divided into small cubical subvolumes (“dipoles”) whose interactions are approximated based on the volume integral equation for the electric field [2]. In principle, the DDA and the corresponding computer codes are applicable to arbitrary incident fields. However, practical simulations for any beam types are much more accessible to the practitioners if they are built into the code. Thus, the main goal of this work is the implementation of Bessel beams in the open-source ADDA code [2].

On one hand, the simplest description is available for linearly polarized beams associated with linearly polarized Hertz potentials of electric (e−) or magnetic (m−) type [1]. The last two types are linearly independent, even if we consider both x- and y-polarization for each type. On the other hand, there exist axisymmetric beams which are a superposition of linearly polarized beams of e− and m− types. They are interesting because they correspond to quasi-Bessel beams obtained by using a conical lens. Therefore, we decided to implement all these types of Bessel beam in the ADDA code. Each of them is described by the corresponding command line option: “−beam besselCS” and “−beam besselLP”, with five parameters: order, convergence angle (tilt angle of a conical lens), and three coordinates of the beam center (relative to the center of the scatterer).

We plan to finish and test the implementation by the time of the conference. As a result, it will be straightforward for anyone to simulate the scattering of Bessel beams by arbitrary inhom*ogeneous particles.

References [1] Wang, J. J., and T. Wriedt, 2016: General description of transverse mode Bessel beams and construction

of basis Bessel fields. J. Quant. Spectrosc. Radiat. Transfer 196, 8–17.[2] Yurkin, M. A., and A. G. Hoekstra, 2011: The discrete-dipole-approximation code ADDA: capabilities

and known limitations. J. Quant. Spectrosc. Radiat. Transfer 112, 2234–2247.

Preferred mode of presentation: Oral/Poster

Effect of internal structure of aerosol on particle optics

Vikas Goela,b, Sumit K. Mishraa,b*, Ajit S. Ahlawata,b, Prashant Kumarc,T. D. Senguttuvana,b, Chhemendra Shramaa,b, and Jeffrey S. Reidd

aEnvironmental Sciences and Biomedical Metrology Division, CSIR–National Physical Laboratory, New Delhi, India – 110012

bAcademy of Scientific and Innovative Research, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh, India – 201002

cGlobal Centre for Clean Air Research, Department of Civil and Environmental Engineering, University of Surrey Guildford GU2 7XH, Surrey, United Kingdom

dUnited States Naval Research Laboratory, Washington DC, USA

*Presenting author ([emailprotected])

Aerosol plays a vital role in the Earth’s radiation budget by scattering and absorbing the incom-ing solar radiation. In general, the aerosol particles are considered as chemically hom*ogeneous spheres in the retrieval techniques of ground and space borne observations [1,2]. Here it is note-worthy to mention that the atmospheric particles (especially dust particles) are highly nonspheri-cal in nature [3,4] and the aforesaid assumption may lead to erroneous observations in retrievals. For better simulation of optical and radiative properties of aerosols, a good knowledge of aero-sol’s morphology, chemical composition and internal structure is essential [5,6].

In present work, we characterize the PM10 (particulate matter with aerodynamic diameter less than 10 µm) particles collected form typical arid (the Thar Desert, Rajasthan, India) and typical urban (New Delhi, India) environments. The particles were milled several times to investigate their internal structure. The EDS (Energy Dispersive X-ray Spectroscopy) spectra were recorded after each milling to check the variation in the chemical composition. In arid environment, Fe, Ca, C, Al, and Mg rich shell was observed over a Si rich particle. In urban environment, shell of Hg, Ag, C, and N was observed over a Cu rich particle. Based on the aforesaid observations, dif-ferent model shapes [single species hom*ogenous sphere (S1) and spheroid (SPH1); multiple spe-cies mixture hom*ogeneous sphere (S2) and spheroid (SPH2); and core shell (CS)] have been considered for simulating their respective optical properties.

Spectral variation of SSA for the considered model shapes (S1, SPH1, S2, SPH2 and CS).

In case of Si rich particle having shell of Fe, Ca C, Al and Mg, SSA (Single Scattering Albe-do) was calculated for the aforementioned model shapes using core-shell optical models (fig. 1). SSA for CS has been observed to be in between the S1, SHP1 and S2, SPH2. This is attributed to the chemical composition of the respective model shapes. For S1 and SPH1 (only quartz), the SSA tends to 1 while the same found to be reduced (b/w 0.5 to 0.6) for S2 and SPH2 (hom*oge-neous mixture of BC, Fe2O3, CaCO3, Al2O3 and MgO). The optics of the other analyzed particles will be discussed in detail during presentation.

References

[1] Mishra, S. K., S. N. Tripathi, S. G. Aggarwal, and A. Arola, 2012: Optical properties of accumulationmode, polluted mineral dust: effects of particle shape, hematite content and semi-external mixingwith carbonaceous species. Tellus B 64, 18536.

[2] Mishra, S. K., and S. N. Tripathi, 2008: Modeling optical properties of mineral dust over the IndianDesert. J. Geophys. Res. 113, D23201.

[3] Mishra, S. K., et al., 2017: Morphology, mineralogy and mixing of individual atmospheric particlesover Kanpur (IGP): relevance of hom*ogeneous equivalent sphere approximation in radiative models.MAPAN 32, 229–241.

[4] Goel, V., et al., 2018: Physico-chemical characterization of individual Antarctic particles: Implica-tions to aerosol optics. Atmos. Environ. 192, 173–181.

[5] Dubovik, O., et al., 2002: Variability of absorption and optical properties of key aerosol types ob-served in worldwide locations. J. Atmos. Sci. 59, 590–608.

[6] Ahlawat, A., S. K. Mishra, V. Goel, C. Sharma, B. P. Singh, and A. Wiedensohler, 2019: Modellingaerosol optical properties over urban environment (New Delhi) constrained with balloon observation.Atmos. Environ. 205, 115–124.

Preferred mode of presentation: Oral

Laser light scattering particle sizing: inherent limitations and effects of optical model selection, unknown refractive index, and irregular particle shape Juan Carlos Gómez Martína, Daniel Guiradoa*, Jesús Escobar-Cerezoa,b, Olga Muñoza, Fernando Morenoa, and Evgenij Zubkoc

aInstituto de Astrofísica de Andalucía – CSIC, 18008, Granada, Spain bDepartment of Physics, University of Helsinki, Finland cFar Eastern Federal University, 8 Sukhanova Street, Vladivostok 690950, Russia *Presenting author ([emailprotected]) Measuring the size distribution of dust particle clouds is of interest in many scientific and techno-logical fields. Inversion of the phase function measured by laser light scattering (LLS) [2] is one of the most widely used sizing methods, owing to its speed, bulk-representative sampling, suita-bility for a wide range of sizes and materials and ease of use [2]. In this presentation, we briefly review different aspects of LLS, including instrumental features, inversion techniques and scatter-ing models. We show that the LLS method using the Mie optical model retrieves robustly size distributions of spherical particles for particle radii r ≥ 0.2 μm, while the upper limit is determined by how close to zero scattering angle (θ) the measurements are performed. The retrieval of size distributions is very sensitive to overestimating the absorption coefficient and underestimating the real part of the refractive index in the small particle range for r < 10 μm. The Fraunhofer model can be used in a restricted scattering angle range (θ < 6°) and is valid for very absorbing particles for sizes below 1 μm, while for non-absorbing particles the retrieved size distributions are reliable for r > 3 μm.

Because real world particles are in general irregular, we focus on the application of LLS to the sizing of irregularly-shaped particles (agglomerate debris model [3]) in a critical range where par-ticle size and analysis wavelength are of the same order (0.1 μm – 3 μm). The phase functions modelled with the DDA method in this size range show heavy entanglement of size, refractive index and irregularity effects. It is shown that in this size range reasonable retrievals are obtained for distributions dominated by particles closer to the upper limit of the range (e.g., power-laws with exponent p > –2.5), where size remains the dominant effect. In general, irregularity results in narrower forward scattering peaks and lower scattered intensity at side angles compared to spher-ical analogs. Diffuse scattering inside irregular particles manifest itself in the phase function as an apparent absorption. As a consequence, LLS retrieves distributions with larger effective radius and higher effective absorption coefficient and/or a lower real refractive index. It can be inferred that the use of the scattering pattern of model particles (spherical or irregularly-shaped) with an internal structure different to that of the real samples under study in order to determine the real and imag-inary parts of their refractive index may result in wrong estimates, e.g. a higher absorption coeffi-cient if the model particles are more compact. Accounting for this requires a characterization of the additional absorption and extended size range as a function of the internal structure (packing density) of the particles under study.

References

[1] ISO (2009), ISO 13320-1 Particle Size Analysis – Guidance on laser diffraction methods.[2] Rawle, A., 2002: The importance of particle sizing to the coatings industry Part 1: Particle size

measurement. Adv. Colour Sci. Technol. 5, 1–12.[3] Zubko, E., K. Muinonen, O. Muñoz, T. Nousiainen, Y. Shkuratov, W. Sun, and G. Videen, 2013: Light

scattering by feldspar particles: Comparison of model agglomerate debris particles with laboratorysamples J. Quant. Spectrosc. Radiat. Transfer 131, 175–187.

Preferred mode of presentation: Oral

Estimating the effective phase function of cloud particles from the 3MI sensor

Souichiro Hiokia,*, Jérôme Riedia, Laurent Labonnotea, Mohamed Djellalia,and Huazhe Shanga,b aUniv. Lille, UMR 8518 – LOA – Laboratoire d’Optique Atmosphérique, F-59000 Lille, France bInstitute of Remote Sensing and Digital Earth, Chinese Academy of Science, Beijing, China

*Presenting author ([emailprotected])

The phase function of a collection of cloud particles depends on the thermodynamic phase, size distribution, geometric shape, and surface texture of the particles. In situ measurements and remote sensing of the phase function are promising means to study the development and microphysical variation of clouds. For example, multi-viewing satellite instruments, including the Multi-angle Imaging Sperctroradiometer (MISR) sensor and the Polarization and Directionality of the Earth’s Reflectance (POLDER) sensors, are sensitive to the phase function at backward scattering direc-tions and provide unique datasets that are used in the validation of the phase functions for satellite data processing.

An effective approach to investigate the phase function of cloud particles from reflectivity measurements is the Spherical Albedo Difference (SAD) method. In this method, the variation of the retrieved cloud spherical albedo is considered an indication of the difference between the true phase function and the phase function used in the spherical albedo retrieval. We further extend the SAD method to retrieve an effective phase function. The extended algorithm is applied to the syn-thetic data of the Multi-viewing, Multi-channel, Multi-polarisation Imager (3MI) to evaluate the applicability to the new satellite sensor.

The 3MI sensor is a spaceborne imaging spectropolarimeter planned to fly aboard the MetOp Second Generation A satellite platform. The design of the instrument leverages heavily on the POLDER sensors to use most of the expertise we gained through the years of operation of the POLDER sensors. The nominal resolution is 4 km at nadir, and the sensor acquires total and po-larimetric reflectivity at nine wavelengths. In this presentation, we summarize the planned Level-2 cloud products from the 3MI sensor and specifically report on the preliminary results from the application of the effective phase function estimation.

Preferred mode of presentation: Oral/Poster

A parallelized Pseudo Spectral Time Domain Model for the light scattering simulation for aerosol particles with irregular shapes and inhom*ogeneous compositions

Shuai Hu*, Taichang Gao, Lei Liu, and Ming Chen

National Key Laboratory on Electromagnetic Environment and Electro-optical Engineering, National University of Defense Technology, No. 60 Shuanglong Street, Nanjing 211101, China

*Presenting author ([emailprotected])

To improve the precision of climate modeling and atmospheric remote sensing, radiative transfer models (RTM) that can accurately calculate the radiation transferred through the atmosphere with aerosols and cloud are required [1–3]. As the fundamental input parameters for the radiative trans-fer simulation, the light scattering properties of aerosols (especially these in solar spectrum) should be accurately modeled [4–7]. However, due to the irregular shapes and inhom*ogeneous composi-tions of aerosol particles (like mineral dust, soot, etc.), their light scattering processes have not been adequately understood, and substantial uncertainties still remain in their optical properties [8,9]. To simplify the scattering process of aerosol particles, in the RTMs widely used now, non-spherical aerosol particles are usually taken as the spherical ones with equivalent volume or surface area, which will definitely decrease the computational accuracy of radiative transfer [6,10–12]. Many researchers have also found that the nonspherical shapes of aerosol particles exert a signif-icant influence on the polarized components of radiation [6,9,13].

To improve the modeling accuracy of radiative transfer, the scattering properties of aerosol particles with irregular shapes and inhom*ogeneous compositions should be accurately simulated. To this end, a light scattering model for nonspherical particles is established based on the Pseudo Spectral Time Domain Model (PSTD) technique. This model is comprised of three modules, i.e., the preprocessing module, electromagnetic field computational module and scattering parameter calculation module. In this model, the Perfectly Matched Layer with Auxiliary Differential Equa-tion ( ADE–PML), an excellent absorption boundary condition (ABC) in FDTD, is generalized for PSTD scheme, and the weighted Total Field/Scattered Field (TF/SF) technique is employed to introduce the incident light into 3D computational domain. To improve the computational effi-ciency, the model is further parallelized by the OpenMP technique. The modeling accuracy of PSTD is validated against Lorenz–Mie, Aden–Kerker and T-matrix theory for spheres, inhom*oge-neous particles and nonspherical particles, and the influence of the spatial resolution and the thick-ness of ADE–PML on the modeling accuracy is discussed as well. At last, the parallel computa-tional efficiency of the model is also analyzed. The results show that an excellent agreement is achieved between the results of PSTD and those well-tested scattering models, where the simula-tion errors of extinction efficiencies are generally smaller than 1%, indicating the high accuracy of our model. Though with a low spatial resolution, reliable modeling precision still can be achieved by PSTD model, especially for large particles. To suppress the electromagnetic wave reflected by the absorption layers, a 6-layer ADE–PML should be set in the computational domain at least.

References [1] Liou, K. N., 2003: An Introduction to Atmospheric Radiation. Academic Press, San Diego.[2] Zhang, F., Y.-N. Shi, J. Li, et al., 2017: Variational iteration method for infrared radiative transfer in

a scattering medium. J. Atmos. Sci. 74, 419–430.[3] Rao, R., 2012: Modern Optics. Scientific express, Beijing.[4] Sun, W., G. Videen, Q. Fu, and Y. Hu, 2013: Scattered-field FDTD and PSTD algorithms with CPML

absorbing boundary conditions for light scattering by aerosols. J. Quant. Spectrosc. Radiat. Transfer. 131,166–74.

[5] Mishchenko, M. I., and L. D. Travis, 1997: Satellite retrieval of aerosol properties over the ocean using polarization as well as intensity of reflected sunlight. J. Geophys. Res.102,16989–17014.

[6] Dubovik, O., A. Sinyuk, T. Lapyonok, et al., 2006: Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust. J. Geophys. Res.111, D11208.

[7] Hu, S., T. Gao, H. Li, et al., 2016: Effect of atmospheric refraction on radiative transfer in visible and near-infrared band: model development, validation, and applications. J. Geophys. Res. 121, 2349–2368.

[8] Mishchenko, M. I., J. W. Hovenier, and L. D. Travis. 2000: Light Scattering by Nonspherical Parti-cles: Theory, Measurements, and Applications. Academic Press, San Diego.

[9] Cheng, T. H., X. F. Gu, et al., 2010: The reflection and polarization properties of non-spherical aer-osol particles. J. Quant. Spectrosc. Radiat. Transfer 111, 895–906.

[10] Curtis, D. B., B. Meland, and M. Aycibin, 2008: A laboratory investigation of light scattering from representative components of mineral dust aerosol at a wavelength of 550 nm. J. Geophys. Res. 113, D08210.

[11] Han, Y., T. Wang, R. Rao, et al., 2008: Progress in the study of physic-optics characteristics of atmospheric aerosols, Acta Phys. Sin. 57, 7396.

[12] Han, Y., R. Rao, Y. Wang, et al., 2012:Inversive method on atmospheric aerosol scattering phase function. Infrared Laser Eng. 41, 3051.

[13] Herman, M., J. L. Deuzé, A. Marchand, et al., 2005: Aerosol remote sensing from POLDER/ADEOS over the ocean: improved retrieval using a nonspherical particle model. J. Geophys. Res. 110, D10S02.

Preferred mode of presentation: Oral

An effective method of degrading electromagnetic field in resonant inductive power transfer of automotive vehicle for public safety

A. U. Ibrahim*, H. A. Umar, and S. Muhammad

Jigawa State Polytechnic, Dutse, Sani Abacha Way, PMB 7040 Dutse, Nigeria

*Presenting author ([emailprotected], [emailprotected])

Public exposure to high frequency time varying electromagnetic field is a serious threat to human health, and there has been continued resistance to the rapid development of wireless charging in automotive vehicles. Resonant inductive power transfer (RIPT), especially at high power, becomes a source for such electromagnetic stray field. Consequently, compliance to safety standard guide-lines of international and regional regulators could guarantee public safety [1,2].

This work proposes a suitable alternative for degrading such magnetic fields, without adding much complexity to the system. A distinctive mechanism of flux interaction in multichannel RIPT [3,4] has properly been harnessed to degrade the intensity of the potential electromagnetic field reaching general public within a close range. RIPT system of 50 kw/85 Hz has been designed using both single-channel and three-channel topology to compare their extended magnetic stray field at 0.8 m away from the center of the charging zone. Simulation outcomes revealed a significant re-duction of these stray fields by the proposed three-channel system to the tune of 68% when com-pared against the conventional one-channel system. This may expose new possibilities, and could eventually encourage the competitiveness of commercialization of automotive vehicles with wire-less charging facility. This is promising especially for public bus transport where a charging system may be needed at high power.

References [1] Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz). Health

Phys. 99, 818–836, 2010. Maxwell, J. C. A Treatise on Electricity and Magnetism, Vol. 2. Oxford:Clarendon, 1892, pp.68–73.

[2] Maximum exposure levels to radiofrequency fields – 3 kHz to 300 GHz. Australian Radiation Protec-tion and Nuclear Safety Agency (ARPANSA), 2002.

[3] Shijo, T., K. Ogawa, M. Suzuki, Y. Kanekiyo, M. Ishida, and S. Obayashi, 2016: EMI reduction tech-nology in 85 kHz band 44 kW wireless power transfer system for rapid contactless charging of electricbus. IEEE Energy Conversion Congress and Exposition (ECCE), Milwaukee, WI, pp. 1–6.

[4] Ibrahim, A. U., W. Zhong, H. Cui, and D. Xu, 2018: reducing extended magnetic stray field in wirelesscharging systems of electric vehicles. IEEE International Power Electronics and Application Confer-ence and Exposition (PEAC), pp. 1–6.

Preferred mode of presentation: Oral

A global inverse problem: determining the Bond albedo of the Earth

Olli Ihalainena,*, Olli Wilkmanb, Antti Penttiläa, Guanglang Xua, Jyri Näränenb, Jouni Peltoniemib, Sonja Lahtinenb, Niko Kareinenb, Maria Gritsevicha, Markku Poutanenb, Hannu Koivulab, and Karri Muinonena,b aUniversity of Helsinki, Department of Physics, P.O. Box 64, 00014 Helsinki, Finland bFinnish Geospatial Research Institute FGI, P.O. Box 84, 00521 Helsinki, Finland

*Presenting author ([emailprotected])

Accurate knowledge of the Earth’s radiative energy budget is vital for precise climate modeling. This energy budget is determined by the total outgoing emitted radiation and the Earth’s spherical albedo, which determines the ratio between the incident total radiation and the outgoing scattered radiation from the top of the atmosphere (ToA). The current monitoring of the Earth’s emitted total radiation and spherical albedo is mainly based on radiometric satellite measurements that require interpolation.

We propose a method for determining the time evolution of the Earth’s spherical albedo and the emitted total radiation with an unprecedented level of accuracy, using the effects of the Earth's radiation pressure on the satellite orbits along with the imaging data gathered by instruments such as the Earth Polychromatic Imaging Camera on the Deep Space Climate Observatory satellite. In the forward problem, we use a discretized model of the ToA for modeling the imaging data and the acceleration caused by Earth’s radiation pressure on the satellites. The discretization is done using a Hierarchical Equal Area isoLatitude Pixelization scheme for the ToA where we classify segments of the pixelization grid based on the underlying scene type.

This first study uses a simplified model with a small number of unknowns for the ToA, a single wavelength for the emitted radiation as well as the scattered radiation, and a box-wing model for the satellites to solve this global statistical inverse problem. Markov chain Monte Carlo sampling is used to estimate the ToA radiation and its effects on the satellites’ orbits, and to find the best fit to both the acceleration data and the imaging data. Then, numerical integration over the entire globe is used to derive the Earth’s spherical albedo and the emitted radiation along with the uncer-tainties.

We show that the inversion of the spherical albedo and the outgoing emitted total radiation with reasonable accuracy is feasible from the current satellite imaging and space-geodetic meas-urements. Our next aim is to expand our forward model to include a wide wavelength range for the scattered and emitted radiation, a more detailed satellite model, and a more descriptive ToA model.

Preferred mode of presentation: Oral

The angular light scattering function of atmospheric ice crystal ensembles

Emma P. Järvinena,* and Franz M. Schnaiterb aNational Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, USA bKarlsruhe Institute of Technology, Kaiserstraße 12., 76131, Karlsruhe, Germany

*Presenting author ([emailprotected])

Ice crystal sub-micrometer structures have a large effect on their optical properties. Theoretical calculations have shown, that compared to pristine crystals, complex ice crystals produce a flat and featureless scattering phase function with a significantly higher fraction of backscattering (e.g., [1–3]). Changing the radiative properties of ice crystals in general circulation models to those of roughened ice crystals could significantly affect the cloud radiative effect. Satellite measurements have indicated that natural ice crystals have a high degree of surface roughness and the latest MODIS collection 6 (C6) product has incorporated complex and roughened ice crystals [4]. How-ever, the use of roughened ice crystals in general circulation models and in satellite retrievals is not well justified as long as observational evidence of the applicability of these models to represent the optical properties of atmospheric ice crystals is given.

In this contribution, we present in situ measurements of the ice crystal angular light scattering function from four airborne field campaigns. The in situ observations show that a uniform angular light scattering function with a relatively low asymmetry parameter is observed globally, which is the result of a high degree of ice particle complexity observed in these clouds. The measured cloud angular light scattering function was compared to a selection of optical particle models, and it was found that the C6 model best represented the measurements. Lastly, we investigate using the in situ dataset how many ice crystals are needed to reproduce the globally observed uniform angular light scattering function.

References [1] Baum, B. A., P. Yang, A. J. Heymsfield, et al., 2011: Improvements in shortwave bulk scattering and

absorption models for the remote sensing of ice clouds. J. Appl. Meteorol. Clim. 50, 1037–1056.[2] Baran, A. J., 2012: From the single-scattering properties of ice crystals to climate prediction: a way

forward. Atmos. Res. 112, 45–69.[3] Yang, P., L. Bi, B. A. Baum, K.-N. Liou, et al., 2013: Spectrally consistent scattering, absorption, and

polarization properties of atmospheric ice crystals at wavelengths from 0.2 to 100 µm. J. Atmos. Sci.70, 330–347.

[4] Platnick, S., K. G. Meyer, M. D. King, et al., 2017: The MODIS cloud optical and microphysical prod-ucts: Collection 6 updates and examples from Terra and Aqua. IEEE Trans. Geosci. Remote Sens. 55,502– 525.

Preferred mode of presentation: Oral

A new in situ hyper-angular cloud polarimeterfor airborne platforms

Emma P. Järvinena,* and Franz M. Schnaiterb aNational Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, USA bKarlsruhe Institute of Technology, Kaiserstraße 12, 76131, Karlsruhe, Germany

*Presenting author ([emailprotected])

Polarimetric satellite observations provide important information on the cloud phase and particle properties. After the end of the PARASOL mission that carried the POLDER polarimeter in 2013, a future satellite mission PACE will carry a hyper-angular polarimeter (HARP-2) instrument that will be used to retrieve, among others parameters, the cloud droplet size distribution, ice particle shape, and roughness.

For validation of polarimetric satellite observations, it is important to establish a direct link between the cloud optical and microphysical properties. An in situ hyper-angular polarimeter is capable of measuring the cloud properties within meters from the fuselage. The instrument will be designed to measure the rear partial scattering phase function including the rainbow feature with a high angular resolution of less than a tenth of a degree. This information can be used to accurately derive the droplet size distribution in real time. Additionally, the scattered light intensity is split with respect to its polarization components that define the depolarization and polarization ratios of the cloud particles. These measurements can be used to derive information on the cloud phase, ice crystal shape, and surface roughness and will support space-borne observations by CALIOP and HARP-2.

In this contribution, we present the concept of an in situ hyper-angular cloud polarimeter that is currently being developed as a collaboration between National Center for Atmospheric Research and Karlsruhe Institute of Technology. We also present the first measurements performed with a laboratory prototype.

Preferred mode of presentation: Poster

Coating material-dependent differences in modelled lidar-measurable quantities for heavily coated soot particles

Franz Kanngießera,* and Michael Kahnerta,b aDepartment of Space, Earth and Environment, Chalmers University of Technology,

SE-412 96 Gothenburg, Sweden bResearch Department, Swedish Meteorological and Hydrological Institute, Folkborgvägen 12,

SE-601 76 Norrköping, Sweden

*Presenting author ([emailprotected])

Atmospheric soot aerosol particles have a strong impact on the Earth’s climate and a negative impact on air quality and human health [1]. With the help of remote sensing techniques, the sources, transport pathways and sinks can be monitored. The interpretation of remote sensing data requires a thorough understanding of the particles’ optical properties. For individual heavily coated soot particles differences in the refractive index of the coating, i.e., different chemical composi-tions, are among the main sources of uncertainty regarding the linear backscattering depolarisation ratio [2].

The possibility to distinguish between different coating materials based on the depolarisation ratio and the extinction-to-backscatter ratio for a set of heavily coated soot particles following a particle size distribution was investigated. As coating material sulphate and a toluene-based or-ganic material were assumed, whereas the particle size distribution was assumed to follow a log-normal distribution based on in situ field measurements [3]. The depolarisation ratio and the ex-tinction-to-backscatter ratio were calculated using the discrete dipole approximation code ADDA (version 1.2) [4] in conjunction with the morphologically complex particle model described in [2]. The calculations were performed for wavelengths of λ = 355, 532, and 1064 nm, and the results were compared to existing lidar field measurements.

Although there are clear differences in the depolarisation ratio for the different coating mate-rials, the differences in the extinction-to-backscatter ratio are larger; thus the extinction-to-backscatter ratio may provide a more reliable method for distinguishing coating materials than the depolarisation ratio.

References [1] Bond, T., and R.W. Bergstrom, 2006: Carbonaceous particles: an investigative review. Aerosol Sci.

Technol. 40, 27–67.[2] Kanngießer, F., and M. Kahnert, 2018: Calculation of optical properties of light-absorbing carbon with

weakly absorbing coating: a model with tunable transition from film-coating to spherical-shell coating.J. Quant. Spetrosc. Radiat. Transfer 216, 17–36.

[3] China, S., C. Mazzoleni, A. Aiken, A., et al., 2013: Morphology and mixing state of individual freshly emitted wildfire carbonaceous particles. Nat. Commun. 4, 2212

[4] Yurkin, M. A., and A. G. Hoekstra, 2011: The discrete-dipole-approximation code ADDA: capabilities and known limitations. J. Quant. Spectrosc. Radiat. Transfer 112, 2234–2247.

Preferred mode of presentation: Oral

An impedance based formulation for passive radiative cooling system design

Muhammed Ali Kecebasa,*, M. Pinar Mengüçb,c, Ali Kosara,d,e, and Kursat Sendura,d,e aFaculty of Engineering and Natural Sciences, Sabanci University, Orhanli-Tuzla, 34956, Istanbul,

Turkey bDepartment of Mechanical Engineering, Ozyegin University, Cekmekoy, 34794, Istanbul, Turkey cCenter for Energy, Environment and Economy, Ozyegin University, Cekmekoy, 34794, Istanbul, Tırkey dCenter of Excellence for Functional Surfaces and Interfaces, Sabanci University, Orhanli-Tuzla, 34956,

Istanbul, Turkey eSabanci University Nanotechnology and Application Center (SUNUM), Orhanlı, Tuzla, 34956, Istanbul,

Turkey

*Presenting author ([emailprotected])

In recent years, passive radiative cooling has become a widely studied field as a solution to the problem of undesired heat generation problem in open environments. Several forms of daytime radiative cooling devices have been proposed in the literature depending on the applications, e.g., thin-films, metamaterials and those composed of nanoparticles [1–4]. Although various design approaches are reported for radiative coolers, they do not benefit from the existing design ap-proaches that are heavily utilized in microwave and RF applications. Adapting the well-established design techniques from these fields to the problem of passive radiative cooling can have certain advantages over the existing design approaches in terms of performance and efficiency.

To demonstrate the possibility of such an adaptation, we developed a semi-analytical design method with thin-films of preselected materials based on impedance matching. Although imped-ance matching with transmission lines is heavily utilized in microwave and RF applications, it has not been adapted to problem of designing optical filters [5,6]. We demonstrate that the proposed method is applicable for designing additional layers that enhance the cooling power of existing thin-film structures. It can be easily applied to any thin-film system to design additional layers for various purposes, e.g. protection or cooling power enhancement, without degrading the optical performance of the existing system. In light of this study, several other impedance matching ap-proaches can be adapted to design various optical structures.

This material is based upon work supported by the Air Force Office of Scientific Research (Aerospace Materials for Extreme Environments Program, PM: Dr. Ali Sayir) under award number FA9550-17-1-0092.

References [1] Raman, A. P., M. A. Anoma, L. Zhu, E. Rephaeli, and S. Fan, 2014: Passive radiative cooling below

ambient air temperature under direct sunlight. Nature 515, 540–544.[2] Rephaeli, E., A. Raman, and S. Fan, 2013: Ultrabroadband photonic structures to achieve high-perfor

mance daytime radiative cooling. Nano Lett. 13, 1457–1461.[3] Bao, H., C. Yan, B. Wang, X. Fang, C. Y. Zhao, and X. Ruan, 2017: Double-layer nanoparticle-

based coatings for efficient terrestrial radiative cooling. Sol. Ener. Mater. Sol. Cells 168, 78–84.[4] Kecebas, M. A., M. P. Mengüç, A. Kosar, and K. Sendur, 2017: Passive radiative cooling design with

broadband optical thin-film filters. J. Quantit. Spectrosc. Radiat. Transfer 198, 179–186. [5] Razavi, B., and R. Behzad, 1998: RF Microelectronics, Vol. 1. Prentice Hall, Upper Saddle River, NJ.[6] Balanis, C. A., 1992: Antenna theory: a review. Proc. IEEE 80, 7–23.

Preferred mode of presentation: Oral

Atmospheric particle in-situ imaging and classifying with digital holography

Osku Kemppinen*, Ryan Mersmann, Jesse Laning, and Matthew J. Berg

Department of Physics, Kansas State University, 1228 N. 17th St., Manhattan, KS 66506, USA

*Presenting author ([emailprotected])

Digital holography is a contact-free imaging method that can work with a naturally flowing air stream. We have built a prototype model for a lightweight, low-cost digital holography instrument, titled HAPI, that can image coarse-mode aerosol particles, with sizes ranging from tens of mi-crometers up to millimeters, in the atmosphere. We have also developed the necessary algorithms to automatically reconstruct the particles’ two-dimensional silhouettes and classify them into par-ticle species. The instrument is flown on a drone for easy deployment and three-dimensional sam-pling.

The instrument concept will allow imaging large atmospheric particles almost anywhere in the lower boundary layer with minimal set-up required, and with very low operational costs. We ex-pect the instrument will greatly add to the knowledge of coarse-mode aerosol particle morphology, and we hope to create an aerosol shape database that can be used to improve various atmospheric simulations and retrievals. In this presentation we show the first results of our measurements.

Preferred mode of presentation: Oral/Poster

Application of multiple scattering theory to Doppler velocimetry of ejecta from shock-loaded samples

A. N. Kondrat’eva,*, A. V. Andriyasha, S. E. Kuratova, and D. B. Rogozkina,b aDukhov Research Institute of Automatics (VNIIA), Suschevskaya ulitza 22, Moscow 127055, Russia bMoscow Engineering Physics Institute (National Research Nuclear University), Kashirskoe Shosse 31,

Moscow 115409, Russia

*Presenting author ([emailprotected])

The presentation addresses the actual problem of recovering the physical parameters of ejecta from data of heterodyne Doppler velocimetry (see, e.g., [1–3]). The spectral profile of heterodyne beats underlies our analysis of experimental data. Under the assumption that ejected fragments are randomly spaced and their number within the probed volume is great, the noise-free component of | | is shown to be expressed in terms of a solution to the transport equation for the field correlation function which accounts for multiple scattering and absorption of the probing beam in the cloud of moving particles. This provides a means of theoretical modeling of experimental Dop-pler data.

The ejecta cloud is considered a plane layer of particles moving in the air away from the free-surface. The spatial profile of the extinction coefficient and the cloud thickness are related directly to the distribution of ejected particles over velocities and coordinates. The slowing-down of ejected particles in the air leads to an ambiguous relation between the particle position and its velocity at different moments of time, resulting in essential complication of this distribution. We calculate the particle distribution over velocities and coordinates using a multi-group representation.

In the report we give a generalization of the results in [3] with allowance for the multi-group representation of the ejecta cloud. In this case the transport equation is reduced to a system of linked Milne-like equations. Furthermore, a finite radius of the probing beam is considered. We solve the system numerically with a discrete ordinate program. The spectrum of the backscattering signal is calculated with the discrete Fourier transform. Varying the values of the cloud optical thickness and the parameters of the particle distribution over velocities and sizes, we fit the calcu-lated spectrum to the time-resolved data of heterodyne Doppler measurements. This approach en-ables us to recover the primary ejecta characteristics (the density–velocity profile, the total ejected mass, and the size distribution of ejected particles) directly from optoheterodyne experiments.

An application of the proposed method to the velocimetry data on ejecta from metal samples is presented.

References [1] Andriyash, V., M. V. Astashkin, V. K. Baranov, et al., 2016: J. Exper. Theor. Phys. 122, 970.[2] Franzkowiak, J.-E., G. Prudhomme, P. Mercier, et al., 2018: Rev. Sci. Instrum. 89, 033901.[3] Andriyash, V. M., V. Astashkin, V. K. Baranov, et al., 2018: J. Appl. Phys. 123, 243102.

Preferred mode of presentation: Oral

Physical optics method for solving light scattering problem for large particles over all scattering directions

Alexander A. Konoshonkin*, Anatoli G. Borovoi, Natalia V. Kustova, Victor A. Shishko, and Dmitriy N. Timofeev

V. E. Zuev Institute of Atmospheric Optics SB RAS, Akad. Zuev sq. 1, 634055 Tomsk, Russia

*Presenting author ([emailprotected])

The physical optics method [1] developed at the V. E. Zuev Institute of Atmospheric Optics has been successfully used to solve the light scattering problem for atmospheric ice crystals in the backward scattering direction for lidar applications [2]. The solution of the light scattering problem for ice crystals ranging in size from 10 to 1000 micrometers (size parameters from 60 up to 6000) has been obtained with this method. For small particles, the physical optics approximation is in good agreement with exact numerical methods [3] (such as the DDA and FDTD), while for large particles the solution converges to the solution obtained within the framework of the geometrical optics approximation.

The talk presents a modification of the physical optics method that allows one to obtain a solution to the light scattering problem over all scattering angles (the entire sphere of scattering directions). It shows that starting from a size parameter of 50 the solution agrees well with the solution obtained by the ADDA. Since the computational complexity of the method does not in-crease with increasing particle size, while the accuracy of the method, on the contrary, becomes better, the physical optics method is a promising technique for solving the light scattering problem for particles much larger then the wavelength of the incident light. In the report, the capabilities of the method are exemplified by solving the light scattering problem for a large fraction of dust aerosol particles.

References [1] Borovoi, A., A. Konoshonkin, and N. Kustova, 2014: The physical-optics approximation and its appli-

cation to light backscattering by hexagonal ice crystals. J. Quant. Spectrosc. Radiat. Transfer 146, 181–189.

[2] Konoshonkin, A., Z. Wang, A. Borovoi, N. Kustova, D. Liu, and C. Xie, 2016: Backscatter by azimuth-ally oriented ice crystals of cirrus clouds. Opt. Express 24, A1257–A1268.

[3] Konoshonkin, A., A. Borovoi, N. Kustova, et al., 2017: Light scattering by ice crystals of cirrus clouds:From exact numerical methods to physical-optics approximation. J. Quant. Spectrosc. Radiat. Transfer195, 132–140.

Preferred mode of presentation: Oral

Extinction matrix for cirrus clouds in the visible and infrared regions

Alexander A. Konoshonkin*, Anatoli G. Borovoi, Natalia V. Kustova, Victor A. Shishko, and Dmitriy N. Timofeev

V. E. Zuev Institute of Atmospheric Optics SB RAS, Akad. Zuev sq. 1, 634055 Tomsk, Russia

*Presenting author ([emailprotected])

The state of polarization of the transmitted radiation varies along the propagation path in scattering media if the media contains a lot of independent nonspherical particles with preferential orienta-tions. This phenomenon is caused by the interference of the incident field with the fields scattered in the forward direction by each particle. One of the examples of such scattering media are cirrus clouds consisting of ice crystals, since the crystals are often oriented quasi-horizontally. The abovementioned interference effects are completely described by the extinction matrix. For ice crystals of cirrus clouds, the matrix was considered by several authors. In particular, the extinction matrix was numerically calculated in [1] with the DDA for small particles. The PO calculations of the extinction matrix for large particle were recently reported in [2,3]. However, [2,3] are based on the assumption of a narrow particle size distribution; as a result, quickly oscillating functions appear. In nature, crystal size distributions are wide, which largely suppresses the oscillating in-terference effects.

The talk presents the extinction matrix for cirrus clouds calculated for the visible and infrared regions using the physical optics approximation for natural crystal size distributions. The cirrus clouds are modeled as a statistical ensemble of hexagonal ice plates distributed over size and ori-entations according to the gamma and Gaussian laws, respectively. Then, the extinction matrices as functions of the incident wavelength, incident direction, crystal size, and crystal orientation are numerically calculated for the first time. It is shown that the off-diagonal elements of the matrix are negligible. Therefore, the extinction in cirrus clouds is described with good accuracy by the scalar exponential law.

References [1] Yang, P., M. Wendish, L. Bi, G. Kattawar, M. Mishchenko, and Y. Hu, 2011: Dependence of extinction

cross-section on incident polarization state and particle orientation J. Quant. Spectrosc. Radiat. Trans-fer 112, 2035–2039.

[2] Shefer, O., 2013: Numerical study of extinction of visible and infrared radiation transformed by pref-erentially oriented plate crystals. J. Quant. Spectrosc. Radiat. Transfer 117, 104–113.

[3] Shefer, O., 2016: Extinction of radiant energy by large atmospheric crystals with different shapes J.Quant. Spectrosc. Radiat. Transfer 178, 350–360.

Preferred mode of presentation: Poster

Matrix exponential in C/C++ version of vector radiative transfer code IPOL

Sergey Korkina,b,* and Alexei Lyapustinb aUSRA GESTAR, 7178 Columbia Gateway Drive, Columbia, MD 21046, USA bNASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD 20771, USA

*Presenting author ([emailprotected])

In 2015, our Fortran 90/95 radiative transfer (RT) code IPOL for simulation of multiple scattering of Intensity and POLarization of the monochromatic solar radiation in a plane-parallel atmosphere confirmed high accuracy in a comprehensive polarized (vector) RT codes intercomparison [1]. Since then, we have used IPOL to account for the effect of polarization of light in the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm [2]. However, IPOL requires fur-ther development: speed-up due to neglect of tiny circular polarization in Earth atmosphere, and translation into C/C++ for natural integration with MAIAC.

Similar to RT code Pstar [3], IPOL combines the discrete ordinates and matrix-operator meth-ods. Evaluation of the matrix exponential using eigendecomposition is a key and, arguably, the most time consuming part. The eigendecomposition represents a matrix using its eigenvalues and eigenvectors. In the new C/C++ version of IPOL, we use only left eigenvectors to evaluate the matrix exponential. This is contrary to a common practice of using the right eigenvectors to eval-uate the matrix exponential and the left eigenvectors to avoid the inversion of the matrix of the right ones [3,4].

Recently, we published our approach with independently reproducible test cases in JQSRT [5]. In this talk, besides theoretical background and numerical examples, we will discuss the use of object-oriented programming with GNU Scientific Library (GSL) [6] in computationally intensive software, which the RT code is.

References [1] Emde, C., et al., 2015: IPRT polarized radiative transfer model intercomparison project – Phase A. J.

Quant. Spectrosc. Radiat. Transfer 164, 8–36.[2] Lyapustin, A., et al., 2018: MODIS collection 6 MAIAC algorithm. Atmos. Meas. Tech. 11, 5741–

5765.[3] Ota, Y., et al., 2010: Matrix formulations of radiative transfer including the polarization effect in a

coupled atmosphere–ocean system. J. Quant. Spectrosc. Radiat. Transfer 164, 8–36.[4] Efremenko, D., et al., 2017: A review of the matrix-exponential formalism in radiative transfer. J.

Quant. Spectrosc. Radiat. Transfer 196, 17–45.[5] Korkin, S., and A. Lyapustin, 2019: Matrix exponential in C/C ++ version of vector radiative transfer

code IPOL, J. Quant. Spectrosc. Radiat. Transfer 227, 106–110.[6] https://www.gnu.org/software/gsl (accessed March 8, 2019).

Preferred mode of presentation: Oral

Application of the method of continuity boundary conditions to the problem of wave diffraction on fractal-like bodies of revolution

AlexanerA. Kyurkchan*, SergeyA. Manenkov, and Nadezda I. Smirnova

Moscow Technical University of Communications and Informatics, Aviamotornaya str. 8a, 111024, Moscow, Russia

*Presenting author ([emailprotected])

The three-dimensional vector problem of diffraction of a plane wave on an ideal conducting body of revolution is solved. The technique proposed in the present work makes it possible to model the scattering characteristics, including the orientations averaged over the angles, for bodies of revo-lution of practically any geometry. The stated problem was solved using the method of continued boundary conditions [1]. The integral equation of the second kind with respect to some unknown function distributed on the surface of the scatterer is obtained. For the numerical solution of the integral equation, we used the expansion of the Green function and the right side into a Fourier series. To solve one-dimensional integral equations for the Fourier harmonics of the unknown function the Krylov–Bogolyubov method is used [2]. Formulas that make it possible to calculate the scattering pattern averaged over the angles of incidence of the plane wave are obtained.

A number of examples of solving problems of diffraction on different particles in particular fractal-like bodies of revolution [3] are given. The correctness of the method is confirmed by ver-ifying the accuracy of the fulfilment of the optical theorem for various bodies and by comparison with the results of calculations obtained by the modified auxiliary current method [1,2].

References [1] Kyurkchan, A. G., and N. I. Smirnova, 2015: Mathematical Modeling in Diffraction Theory Based on

A Priori Information on the Analytic Properties of The Solution. Elsevier, Amsterdam.[2] Manenkov, S. A., 2014: The modified auxiliary current method applied for the problem of diffraction

by a body of revolution with a kinked boundary. J. Commun. Technol. Electron. 59, 392–399.[3] Crownover, R. M., 1995: Introduction to Fractals and Chaos. Jones and Bartlett, Boston.

Preferred mode of presentation: Poster

A fast algorithm for multi-particle scattering in a layered medium Jun Lai

School of Mathematical Sciences, Zhejiang University, 38 Zheda Rd., Hangzhou, Zhejiang, 310013, China ([emailprotected])

In this talk, we consider acoustic or electromagnetic scattering in two or three dimensions from an infinite three-layer medium with thousands of wavelength-size dielectric particles embedded in the middle layer. Such geometries are typical of microstructured composite materials, and the eval-uation of the scattered field requires a suitable fast solver for either a single configuration or for a sequence of configurations as part of a design or optimization process. We have developed an algorithm for problems of this type by combining the Sommerfeld integral representation, high order integral equation discretization, the fast multipole method and classical multiple scattering theory. The efficiency of the solver is illustrated with several numerical experiments. Extension to periodic layered medium (grating structure) and applications on inverse scattering problems will be also presented. References [1] Gimbutas, Z., and L. Greengard, 2013: Fast multi-particle scattering: a hybrid solver for the Maxwell

equations in micro structured materials. J. Comput. Phys. 232, 22–32. [2] Greengard, L., and V. Rokhlin, 1987: A fast algorithm for particle simulations. J. Comput. Phys. 73,

325–348. [3] Lai, J., M. Kobayashi, and L. Greengard, 2014: A fast solver for multi-particle scattering in a layered

medium. Opt. Express 22, 20481–20499. [4] Lai, J., M. Kobayashi, and A. Barnnet, 2015: A fast and robust solver for the scattering from a layered

periodic structure containing multi-particle inclusions. J. Comput. Phys. 298, 194–208 [5] Lai, J., M. Li, P. Li, and W. Li, 2018: A fast direct imaging method for the inverse obstacle scattering

problem with nonlinear point scatterers. Inv. Probl. Imag. 12, 635–665. Preferred mode of presentation: Oral

Meta-trapping: optical forces on meta-materials

Isaac C. D. Lenton*, Timo A. Nieminen, Alex B. Stilgoe, and Halina Rubinsztein-Dunlop

School of Mathematics and Physics, The University of Queensland, St. Lucia, Brisbane QLD 4072, Aus-tralia

*Presenting author ([emailprotected])

In recent years there has been a lot of interest in the field of meta-materials. Progress in this field has been aided by advances in fabrication technologies that led to the realization of both micro-wave and optical meta-materials [1]. These materials offer the ability to create perfect lenses, in-visibility cloaks and control the directionality of scattering [2]. They also allow the creation of new types of optically trapped particles which could be useful for microscopic force probes or use in fundamental science. The possibility to engineer how these particles scatter light could be useful for improving optical trap depth or improving the measurement sensitivity by maximizing light scattered in a particular direction. Full understanding of how these particles scatter light is neces-sary for intelligently engineering particles or the light fields that manipulate these particles for particular applications.

For spherical particles, the solutions for the scattered field are exact. We can simulate the scattering of these particles by calculating the Mie coefficients with arbitrary values for the per-mittivity and permeability [3]. The forces acting on the particle can be found by calculating the change in momentum of the scattered light. In order to understand the optical forces on these exotic particles, we consider a vector spherical mode expansion of the scattering in order to look at the different contributions to the force from different modes.

In this presentation we will provide a visual guide for the types of particles which can be optically trapped. We will consider absorbing and emitting materials, particles with non-unity rel-ative permeability and special cases such as zero back scattering particles and trapping of refrac-tive-index matched particles. Beginning with particles which only scatter into the dipole mode, we will then extend the work to the quadrupole mode and higher order modes. We will discuss how these modes can be engineered to enhance optical trapping, either by engineering the beam or the particle. And finally, we will discuss what the results mean for optical trapping of spherical particles in a simple focused Gaussian beam.

References [1] Tanaka, T., and A. Ishikawa, 2017: Towards three-dimensional optical metamaterials. Nano Conver-

gence 4, 34.[2] Liu W., et al., 2018: Generalized Kerker effects in nanophotonics and meta-optics. Opt. Express 26,

13085–13105.[3] Kerker, M., et al., 1983: Electromagnetic scattering by magnetic spheres. J. Opt. Soc. Am. 73, 765–

767.

Preferred mode of presentation: Oral

Estimation of surface solar radiation by Voronoi ice scattering model from Himawari-8 satellite measurements

Husi Letua,b, Takashi Y. Nakajimab, Hiroshi Ishimotoc, Run Maa, and Huazhe Shanga aInstitute of Remote Sensing and Digital Earth, Chinese Academy of Sciences (CAS), DaTun Road No. 20

(North), Beijing 100101, China bResearch and Information Center (TRIC), Tokai University, 4-1-1 Kitakaname Hiratsuka,

Kanagawa 259-1292, Japan cMeteorological Research Institute, Japan Meteorological Agency (JMA), Nagamine 1-1,

Tsukuba 305-0052, Japan

*Presenting author ([emailprotected])

Himawari-8 is a new-generation geostationary meteorological satellite which is successfully launched by the Japan Meteorological Agency on 7 October 2014. The Himawari-8 carries the multi-spectral Advanced Himawari Imager (AHI). In this study, cloud optical and microphysical properties are retrieved from Himawari-8 satellite measurements. Fractal ice partial scattering model called “Voronoi” [1,2] is applied in the Comprehensive Program for Cloud Optical Meas-urement algorithm to retrieve ice cloud properties from AHI measurements [3,4]. Retrieval results from AHI are used to estimate the surface solar radiation (SSR) using the Rstar radiative transfer model. Furthermore, AHI cloud property retrievals are compared to the MODIS C6 cloud property product. Finally, SSR data derived from AHI cloud properties is validated using ground-based observation data.

References [1] Ishimoto, H., K. Masuda, Y. Mano, N. Orikasa, and A. Uchiyama, 2012: Irregularly shaped ice aggre-

gates in optical modeling of convectively generated ice clouds. J. Quant. Spectrosc. Radiat. Transfer113, 632–643.

[2] Letu, H., H. Ishimoto, R. Jerome, T. Y. Nakajima, C. Labonnote, A. Baran, K. T. Nagao, and M.Sekiguchi, 2016: Investigation of ice particle habits to be used for ice cloud remote sensing for theGCOM-C satellite mission. Atmos. Chem. Phys. 16, 12287–12303.

[3] Nakajima, T. Y., and T. Nakajima, 1995: Wide-area determination of cloud microphysical propertiesfrom NOAA AVHRR measurements for FIRE and ASTEX regions. J. Atmos. Sci. 52, 4043–4059.

[4] Letu, H., T. M. Nagao, T. Y. Nakajima J. Riedi, H. Ishimoto, A. J. Baran, H. Shang, M. Sekiguchi, andM. Kikuchi, 2018: Ice cloud properties from Himawari-8/AHI next-generation geostationary satellite:Capability of the AHI to monitor the DC cloud generation process. IEEE Trans. Geosci. Remote Sens.,DOI: 10.1109/TGRS.2018.2882803.

Preferred mode of presentation: Oral

Diurnal variability of aerosol type and vertical distribution and its implication for satellite aerosol remote sensing

Jing Li* and Chong Li

Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China

*Presenting author ([emailprotected])

Aerosols vary on different time scales. Compared to seasonal or interannual variability, the diurnal variability of aerosol properties is less studied, mainly because continuous monitoring of aerosol properties over the course of a day is only available at scattered ground sites. However, with the increasing attention being paid to satellite retrievals using geostationary platforms, accurate eval-uation of diurnal changes of aerosol properties becomes essential. In this study, we investigate the changes of aerosol optical parameters and vertical distribution using aethalometer, nephelometer, sunphotometer, and lidar measurements in Beijing. A distinct diurnal cycle is found in all these parameters, which are mainly related to the development of the planetary boundary layer but also to other meteorological factors such as winds and humidity. We further use AERONET data to classify aerosols into four major types: dust, fine absorbing, fine scattering, and mixed. We find that in addition to Beijing, significant diurnal changes of aerosol type are noticed at many world-wide locations, in particular, Western US, Southwestern Europe, and South Africa. We further use the 6s radiative transfer model to evaluate the impact of these diurnal changes on aerosol retrievals from geostationary platforms. Specifically, we compare the difference between the retrieved aer-osol optical thickness using the mean aerosol model and vertical distribution and that using diur-nally resolved values. Large discrepancies, up to 50%, are found between these two values. Our results indicate that diurnal changes of aerosol type and vertical distribution represent a common phenomenon and must not be neglected in aerosol retrievals using geostationary satellites.

Preferred mode of presentation: Oral

Aspect ratio distributions of atmospheric aerosol particles and their effects on skylight polarization

Li Lia,*, Zhengqiang Lia, Xu Zhengb, Oleg Dubovikc, Zhanhua Lib, and Manfred Wendischd aState Environmental Protection Key Laboratory of Satellite Remote Sensing, Aerospace Information

Research Institute, Chinese Academy of Sciences, Beijing 100101, China bInstitute of Mechanics, Chinese Academy of Sciences, 100190, Beijing, China cLaboratoire d’Optique Atmosphérique, Université de Lille 1/CNRS, 59655, Lille, France dLeipzig Institute for Meteorology, Leipzig University, 04103, Leipzig, Germany

*Presenting author ([emailprotected])

Atmospheric aerosol particles modify the radiative energy budget of the earth–atmosphere system by scattering and absorbing solar radiation. Considering that particle morphology is of vital im-portance to how electromagnetic radiation is scattered by a single particle and that light scattering is affected by the shape distribution of volume particles, quantitative knowledge about various non-spherical aerosol shapes gets more and more attention in modelling aerosol volumetric optical properties [1,2]. The shape distribution, expressed as aspect ratio distribution, is derived as the normalized number of the occurrence of aspect ratios of a large sample of individual particles. An a priori fixed shape distribution of dust particles has widely been applied in the inversion of aero-sol particle properties based on measurements collected with sun-sky radiometers. This dust par-ticle shape distribution derived from laboratory measurements shows obvious different features compared to the results obtained by direct microscopic observations of aerosol particle samples captured in the natural atmosphere [2].

In this talk, we employ the model of polydisperse randomly oriented spheroids and use a fluo-rescence microscope to measure the aspect ratio distribution of atmospheric aerosol particles. The effects of different directly microscope-measured and indirectly inversion-based aerosol shape dis-tributions on the radiance and polarization distributions of the skylight in the celestial hemisphere are discussed based on numerical simulations. The results suggest that using representative particle shape distributions obtained by direct microscopic observations of aerosol samples captured in natural atmosphere could improve the retrieval of aerosol shape parameter [3].

References [1] Wendisch, M., and P. Yang, 2012: Theory of Atmospheric Radiative Transfer: A Comprehensive Intro-

duction. Wiley-VCH, Weinheim, Germany.[2] Li. L., X. Zheng, Z. Q. Li, et al., 2017: Studying aerosol light scattering based on aspect radio distribu-

tion observed by fluorescence microscope. Opt. Express. 25, A813–A823.[3] Li L., Z. Q. Li, X. Zheng, et al., 2019: Effects of the shape distribution of aerosol particles on their

volumetric scattering properties and the radiative transfer through the atmosphere that includes polari-zation. Appl. Opt. 58, 1475–1484.

Preferred mode of presentation: Poster

Measurement of drops with inclusions using rainbow refractometry and time-shift technique

Can Lia,b,*, Lingxi Lia, Cameron Tropeaa, Xuecheng Wub, and Yingchun Wub

aInstitute of Fluid Mechanics and Aerodynamics, Technische Universität Darmstadt, 64287, Darmstadt, Germany

bState Key Lab of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China

*Presenting author ([emailprotected])

Characterization of drops with inclusions is of great practical interest and has wide industrial ap-plications, for instance spray drying or paint spraying [1]. Reported here is an investigation to simultaneously measure the key parameters (i.e., droplet size, liquid refractive index, drop velocity and inclusion concentration) of a drop with inclusions using rainbow refractometry [2] and the time-shift technique [3].

In this work, a piezoelectric monodisperse droplet generator generates a stream of water drops with a size of 70–200 μm. Polystyrene particles with a diameter of 300 ± 30 nm are dispersed in the distilled water with different concentrations by controlled dilution [4]. With rainbow refrac-tometry the concentration of inclusions can be estimated from the intensity extinction of the rain-bow peak and with the time-shift technique an intensity ratio of reflected light to refracted light is employed. Experimental results will be compared with simulated results obtained using a Monte Carlo ray tracing approach [3,5].

References [1] Tropea C., 2011: Optical particle characterization in flows. Annu. Rev. Fluid Mech. 43, 399–426.[2] Li, C., X. C. Wu, J. Z. Cao, L. H. Chen, G. Gréhan, and K. F. Cen, 2018: Application of rainbow

refractometry for measurement of droplets with solid inclusions. Opt. Laser Technol. 98, 354–362.[3] Li, L., S. Rosenkranz, W. Schäfer, and C. Tropea, 2019: Light scattering from a drop with an embedded

particle and its exploitation in the time-shift technique. J. Quant. Spectrosc. Radiat. Transfer 277, 20–31.

[4] Savo, R., R. Pierrat, U. Najar, R. Carminati, S. Rotter, and S. Gigan, 2017: Observation of mean pathlength invariance in light-scattering media. Science 358, 765–768.

[5] Mishchenko, M. I., and A. Macke, 1997: Asymmetry parameters of the phase function for isolated anddensely packed spherical particles with multiple internal inclusions in the geometric optics limit. J.Quant. Spectrosc. Radiat. Transfer 57, 767–794.

Preferred mode of presentation: Oral

A study for the measurement of the drop concentration by using the time-shift technique

Lingxi Lia,*, Simon Rosenkranzb, Walter Schäferb, and Cameron Tropeaa

aInstitute of Fluid Mechanics and Aerodynamics, Technische Universität Darmstadt, 64287, Darmstadt, Germany

bAOM-Systems GmbH, 64646 Heppenheim, Germany

*Presenting author ([emailprotected])

Colloidal drops are encountered frequently in numerous process industries, such as in pharmaceu-tical products or spray drying to produce powders. However, current optical measurement tech-niques are not capable of measuring the solid particle concentration in such drops [1]. The present study is devoted to the measurement of drop size and particle concentration of colloidal drops using the time-shift technique [2]. This work builds on first results reported in [3], in which a Monte Carlo ray tracing method was used to predict the time-shift signal received from two-di-mensional drops. In the current work, the ray tracing code has been expanded to consider a three-dimensional drop using algorithms described in [4,5]. This approach, building on geometric optics, is more feasible in terms of computational effort than alternative methods (e.g., the discrete dipole approximation, or DDA), especially for larger drops and when the entire passage of the drop through the focused beam of the time-shift device must be captured. However, the DDA can be used to compute the signal amplitude for certain positions of the drop in the illuminating beam, and these results can be compared with the results from the Monte Carlo ray tracing method. The outcome of this investigation is a recommendation of signal processing steps necessary to estimate solid particle concentrations in drops from time-shift signals.

References [1] Tropea C., 2011: Optical particle characterization in flows. Annu. Rev. Fluid Mech. 43, 399–426.[2] Schäfer, W., and C. Tropea, 2014: Time-shift technique for simultaneous measurement of size, velocity

and relative refractive index of transparent droplets or particles in a flow. Appl. Opt. 53, 588–596.[3] Rosenkranz, S., W. Schäfer, C. Tropea, and A. M. Zoubir, 2016: Modeling photon transport in turbid

media for measuring colloidal concentration in drops using the time-shift technique. Appl. Opt. 55,9703–9711.

[4] Raković, M. J., G. W., Kattawar, M. Mehrűbeoğlu, B. D. Cameron, L. V. Wang, S. Rastegar, and G.L. Coté, 1999: Light backscattering polarization patterns from turbid media: theory and experiment.Appl. Opt. 38, 3399–3408.

[5] Li, L., S. Rosenkranz, W. Schäfer, and C. Tropea, 2019: Light scattering from a drop with an embeddedparticle and its exploitation in the time-shift technique. J. Quant. Spectrosc. Radiat. Transfer 277, 20–31.

Preferred mode of presentation: Oral

Impact of H2O broadening effect on high-accuracy atmospheric trace gases detection

Jingsong Lia,*, Hao Denga, Ningwu Liua, Zhou Shena, and Horst Fischerb aLaser Spectroscopy and Sensing Laboratory, Anhui University, 23061 Hefei, China bMax Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany

*Presenting author ([emailprotected])

Unlike other atmospheric gases, the distribution of water vapor (H2O) in the atmosphere varies with high dynamic range, which is strongly dependent on time, location, and altitude. Therefore, the broadening contribution due to water vapor mixing ratio variation would need to be known with a minimal uncertainty for high-accuracy data retrievals, especially in a humid atmosphere. In this study, a tunable quantum cascade laser spectrometer (QCLS) was developed to study H2O broadening coefficients for CO and N2O transitions at the 4.57 μm region which contains well-characterized and relatively isolated transitions of appropriate line strengths for sensitive gas de-tection [1]. The influence of H2O broadening effect on CO R(11) and N2O P(38e) transitions at 2186.639 cm–1 and 2187.099 cm–1, respectively, was investigated in detail [2]. Our measurements indicate that H2O broadening coefficients are 1.8 and 1.9 times higher than the corresponding air-broadening parameters, respectively. Based on the experimental data, our simulation confirmed that the WMS-2f shapes of CO and N2O lines will be significantly affected by variations of the water vapor mixing ratio, while no significant dependence on target concentration, and prove that the difference between air- and H2O-broadenings thus cannot be neglected if one wants to measure gas concentrations in a high humid environment with a sub-percent precision.

References [1] Li, J. S., H. Deng, J. Sun, B. L. Yu, and H. Fischer, 2016: Simultaneous atmospheric CO, N2O and H2O

detection using a single quantum cascade laser sensor based on dual-spectroscopy techniques. Sens.Actuat. B 231, 723–732.

[2] Deng, H., J. Sun, N. W. Liu, H. Wang, B. L. Yu, and J. S. Li, 2017: Impact of H2O broadening effecton atmospheric CO and N2O detection near 4.57 μm. J. Mol. Spectrosc. 331, 34–43.

Preferred mode of presentation: Poster

An update on the extended advanced IEM for scattering from randomly rough surfaces

Yongxing Lia, Jingsong Yangb, J. C. Shic, and Yang Dua,* aZhejiang University, Hangzhou, Zhejiang, 310027 China bSecond Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China cInstitute of Digital Earth and Remote Sensing Applications, Chinese Academy of Sciences, Beijing,

100101, China

*Presenting author ([emailprotected])

In this study we update the extended advanced integral equation model (EAIEM) for electromag-netic backscattering and bistatic scattering from rough surfaces with small to moderate heights. We extend the first order approximation of the error function as introduced in the EAIEM model to the second order, in the hope to be more suitable for large roughness and high frequency. In addition, a new transition model for the reflection coefficient is proposed to make the dependencies explicit on the average surface curvature, incident frequency, and dielectric constant, whereas making no use of the complementary term, so the effect of inadequate evaluation of this term is mitigated. Comparison with POLARSCAT data for backscattering and with EMSL measurements for bistatic scattering demonstrates the validity of the updated model.

Preferred mode of presentation: Oral

Preliminary investigation on single isolated burning droplet using digital in-line holography Haipeng Lia,*, Yingchun Wub, Norbert Rieflera, Thomas Wriedta, Xuecheng Wub, and Lutz Mädlera aLeibniz Institute for Materials Engineering IWT, Faculty of Production Engineering, University of Bre-

men, Bremen, 28359, Germany bState Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China *Presenting author ([emailprotected]) Flame spray pyrolysis (FSP) is a versatile and promising technique for fast and scalable synthe-sizing nanoparticles [1,2]. Because of high phase purity, well crystallinity and well-control of size, the FSP-synthesized nanoparticles have been used for wide functional applications including sen-sors, catalysis, phosphors, electroceramics, batteries, and biomaterials. During FSP process, mass transfer of the precursor from liquid droplet to gas phase decides the product quality. Single droplet combustion has been a very valuable tool for providing fundamental knowledge of the FSP pro-cess.

Hereby we will present our preliminary results on single isolated burning droplet using digital in-line holography (DIH). DIH is a three-dimensional (3D) laser-based measurement technique, which can detect spatial- and time-resolved information of particle shape, velocity and position [3,4]. DIH has been employed to measure coal particles in flames [5], aluminum droplet combus-tion [6], and aerodynamic fragmentation of droplets [7]. Thus, we expect to use DIH to detect droplet 3D motion, droplet explosion, as well as the composition and temperature profiles from droplet surface to flame surface during the single droplet combustion of precursor-solvent solu-tions. References [1] Teoh, W. Y., R. Amal, and L. Mädler, 2010: Flame spray pyrolysis: An enabling technology for nano-

particles design and fabrication. Nanoscale 2, 1324–1347. [2] Li, S., Y. Ren, P. Biswas, and D. T. Stephen, 2016: Flame aerosol synthesis of nanostructured materials

and functional devices: Processing, modeling, and diagnostics. Prog. Ener. Combust. Sci. 55, 1–59. [3] T. C. Poon, and J. P. Liu, (2014). Introduction to Modern Digital Holography: with MATLAB. Cam-

bridge University Press, Cambridge, UK. [4] Wu, Y., X. Wu, L. Yao, et al., 2016: 3D boundary line measurement of irregular particle with digital

holography. Powder Technol. 295, 96–103. [5] Wu, Y., X. Wu, L. Yao, et al., 2017: Simultaneous particle size and 3D position measurements of

pulverized coal flame with digital inline holography. Fuel 195, 12–22. [6] Guildenbecher, D. R., M. A. Cooper, W. Gill, et al., 2014: Quantitative, three-dimensional imaging of

aluminum drop combustion in solid propellant plumes via digital in-line holography. Opt. Lett. 39, 5126–5129.

[7] Guildenbecher, D. R., J. Gao, J. Chen, and P. E. Sojka, 2017: Characterization of drop aerodynamic fragmentation in the bag and sheet-thinning regimes by crossed-beam, two-view, digital in-line holog-raphy. Int. J. Multiphase Flow 94, 107–122.

Preferred mode of presentation: Oral

Assessing superspheroidal dust models in particle scattering and polarized radiative transfer simulations Wushao Lin*, Xiaoyun Tang, and Lei Bi

Department of Atmospheric Sciences, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, China *Presenting author ([emailprotected]) As one of the major atmospheric aerosols, dust has important effect on the Earth’s radiative energy budget and profoundly affects regional and global climate. Although tremendous efforts have been devoted to parameterizing dust optical properties, there has not been a standard and consistent approach to remote sensing and radiative transfer studies. In this presentation, we report on our recent progress made to improve dust optical modeling in a superspheroidal shape space. Su-perspheroids have one more freedom than spheroids. However, the additional freedom can be con-strained by comparing theoretical simulations with laboratory measurements. In this study, the scattering matrices of 25 dust aerosol samples from the Amsterdam–Granada Light Scattering Da-tabase [1] were used. We found that 1) extreme aspect ratios for spheroids in reproducing the measurements were unnecessary if superspheroids were employed [2]; 2) even with equi-probable aspect ratio distribution, concave superspheroids with large roundness parameters (e.g., from 2.4 to 3.0) could concurrently match six nonzero scattering matrix elements from the laboratory meas-urements [2]; 3) superspheroidal models with constrained roundness parameter also exhibit better performances than spheroids in reproducing backscattering ratios that are critical in active Lidar remote sensing [3]. Additionally, to understand the impact of models in atmospheric radiative transfer, we carried out sensitivity studies on how the shape parameters (i.e., aspect ratio and roundness parameter) affect the TOA radiance and polarization simulations. By analyzing model-ing results, the implications of applying superspheroidal dust models in polarized remote sensing will be discussed. References [1] Muñoz, O., F. Moreno, D. Guirado, D. D. Dabrowska, H. Volten, and J. W. Hovenier, 2012: The

Amsterdam–Granada Light Scattering Database. J. Quant. Spectrosc. Radiat. Transfer 113, 566–574. [2] Lin, W., L. Bi, and O. Dubovik, 2018: Assessing superspheroids in modeling the scattering matrices

of dust aerosols. J. Geophys. Res. Atmos. 123, 13917–13943. [3] Tang, X., L. Bi, W. Lin, D. Liu, K. Zhang, and W. Li, 2019: Backscattering ratios of soot-contaminated

dusts at triple LiDAR wavelengths: T-matrix result. Opt. Express 27, A92–A116. Preferred mode of presentation: Poster

A unified-principal-component radiative transfer model Chao Liua,*, Bin Yaoa, Vijay Natrajb, and Yuk L. Yungc aSchool of Atmospheric Physics, Nanjing University of Information Science and Technology,

Nanjing 210044, China bJet Propulsion Laboratory, California Institute of Technology, Pasadena 91125, USA cDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91125,

USA *Presenting author ([emailprotected]) This study presents a fast radiative transfer (RT) model, referred to as the UPCRTM (Unified Principal Component RT model), to calculate the high-spectral resolution radiation. The principal component analysis is used twice independently to reduce the number of accurate RT simulations and subsequently minimize the number of channels for which RT calculations are performed. Thus, by performing many fewer accurate radiative transfer simulations (a few tens), we can get high-spectral resolution results (a few tens of thousands) efficiently without significant loss of accuracy. Gas absorption, aerosol scattering, and Rayleigh scattering can be fully considered in the model, and a comprehensive database by considering a large amount of atmospheric and aerosol profiles over the entire solar spectrum is developed for the PCA-based data training and validation. The UPCRTM is found to be three orders of magnitudes faster than the corresponding accurate models, and shows relatively small errors, generally within 0.5%. The efficiency and accuracy of the UP-CRTM not only enables its application for high-spectral resolution instruments, but also provides a possible method for accurate RT simulations in mesoscale numerical weather models and general circulation models. Preferred mode of presentation: Oral

Time-harmonic acoustic scattering from a non-locally perturbed trapezoidal surface Wangtao Lua,* and Guanghui Hub aZhejiang University, Hangzhou, 310027, China bBeijing Computational Science Research Center, Beijing, 100193, China *Presenting author ([emailprotected]) This paper is concerned with acoustic scattering from a sound-soft trapezoidal surface in two di-mensions.The trapezoidal surface is supposed to consist of two horizontal half-lines pointing op-positely, and a single finite verticalline segment connecting their endpoints, which can be regarded as a non-local perturbation of a straight line. For incident plane waves, we enforce that the scattered wave, post-subtracting reflected plane waves by the two half lines of the scattering surface in cer-tain two regions respectively, satisfies an integral form of Sommerfeld radiation condition at in-finity. With this new radiation condition, we prove uniqueness and existence of weak solutions by a coupling scheme between finite element and integral equation methods. This consequently indi-cates that our new radiation condition is sharper than the Angular Spectrum Representation, and has generalized the radiation condition for scattering problems in a locally perturbed half-plane. Furthermore, we develop a numerical mode matching method based on this new radiation condi-tion. A perfectly matched layer is setup to absorb outgoing waves at infinity. Since the medium composes of two horizontally uniform regions, we expand, in either uniform region, the scattered wave in terms of eigenmodes and match the mode expansions on the common interface between the two uniform regions, which in turn gives rise to numerical solutions to our problem. Numerical experiments are carried out to validate the new radiation condition and to show the performance of our numerical method. Preferred mode of presentation: Oral

Static-limit T-matrix for a dielectric torus Matt R. A. Majic The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical

Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand ([emailprotected])

Semi-analytic expressions for the static limit of the T-matrix for electromagnetic scattering are derived for a circular torus, expressed in either a basis of toroidal harmonics or spherical harmonics. The scattering problem for an arbitrary static excitation is solved using toroidal harmonics, and these are then compared to the extended boundary condition method to obtain analytic expressions for auxiliary Q- and P-matrices, from which T = PQ–1, where these matrices are expressed in a basis of toroidal harmonics. The electrostatic solution for a dielectric torus has been known since 1972 [1] as a combination of a continued fraction and a recurrence relation, rather than a matrix inverse. The method applied here leads to independent calculations of the plasmon resonances, including a set of resonances unobtainable via the continued fraction approach. Also, by applying the basis transformations between toroidal and spherical harmonics, the quasi-static limit of the electric-electric multipole coupling block T22 of [2] is obtained. This allows computations of static limits of the optical cross-sections, and also to obtain analytic expressions for the limit of a thin ring. We discuss the existence of the T-matrix for an object of such a complex shape in the Rayleigh limit. References [1] Love, J., 1972: J. Math. Phys. 13, 1297. [2] Mishchenko, M. I., L. D. Travis, and A. A. Lacis, 2002: Scattering, Absorption, and Emission of

Light by Small Particles. Cambridge University Press, Cambridge, UK. Preferred mode of presentation: Oral

Approximate T-matrix and optical properties of spheroidal particles to third order in size parameter Matt R. A. Majic*, Luke Pratley, Dmitri Schebarchov, Walter R. C. Somerville, Baptiste Auguié, and Eric C. Le Ru The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical

Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand *Presenting author ([emailprotected]) Nanoparticles are widely used for example in chemistry, medicine, cancer treatment, surface enhanced spectroscopy, partly due to their strong electric field enhancements. Shapes such as nano-rods, disks and deformed spheres are commonly approximated in theory by spheroids to obtain analytic results. The most significant property of small illuminated particles is the induced dipole moment, for which there is a simple expression for spheroids in the electrostatic limit – this involves the “static depolarization factors”. There have been attempts to extend this using “dynamic depolarization factors” [1,2], but these extensions are not consistent with the second order series expansion in size-parameter.

In electromagnetic scattering, the so-called T-matrix encompasses the optical response of a scatterer for any incident excitation and is most commonly defined using the basis of multipolar fields [3], generalizing the concept of polarizability of a scatterer. Following our recent paper [4], we calculate the series expansion of the T-matrix for a spheroidal particle in the small-size/long-wavelength limit, up to third lowest order with respect to X. T is calculated from the extended boundary condition method with a linear system involving two infinite matrices P and Q, whose matrix elements are integrals on the particle surface. The limiting form of the P- and Q-matrices for spheroids [5,6], ensures that this Taylor expansion can be obtained by considering only multipoles of order 3 or less (i.e., dipoles, quadrupoles and octupoles). The lowest order is O(X 3) and equivalent to the quasi-static or Rayleigh approximation. Expressions to order O(X 5) are obtained by Taylor expansion of the integrals in P and Q followed by matrix inversion. We then apply a radiative correction, which makes the resulting expressions valid up to order O(X 6). Orientation-averaged extinction, scattering, and absorption cross-sections are then derived.

These results provide a simple alternative to the exact T-matrix method for spheroidal particles smaller than the wavelength, in a size range much larger than for the Rayleigh approximation. The approach also provides details of quadrupole and octopole interactions and their spectral peaks are identified. References [1] Kelly, K. L., E. Coronado, L. L. Zhao, and G. C. Schatz, 2003: J. Phys. Chem. B 107, 668. [2] Moroz, A., 2009: J. Opt. Soc. Am. B 26, 517. [3] Mishchenko, M. I., L. D. Travis, and A. A. Lacis, 2002: Scattering, Absorption, and Emission of Light

by Small Particles. Cambridge University Press, Cambridge, UK. [4] Majić, M. R. A., L. Pratley, D. Schebarchov, W. R. C. Somerville, B. Auguié, and E. C. Le Ru, 2019:

Phys. Rev. A 99, 013853, arXiv:1810.06107.

[5] Somerville, W. R. C., B. Auguié, and E. C. Le Ru, 2012: J. Quant. Spectrosc. Radiat. Transfer 113, 524.

[6] Somerville, W. R. C., B. Auguié, and E. C. Le Ru, 2013: J. Quant. Spectrosc. Rad. Transfer 123, 153. Preferred mode of presentation: Poster

3MI, the multi-view polarimeter flying on Metop-SGA: concept, calibrations, and products Thierry Marbacha,*, Oleg Dubovikb, Bertrand Fougniea, and Jérôme Riedib aEUMETSAT, Eumetsat-Allee 1, 64295 Darmstadt, Germany bUniv. Lille, UMR 8518 – LOA – Laboratoire d’Optique Atmosphérique, F-59000 Lille, France *Presenting author ([emailprotected]) The Multi-Viewing-Channel-Polarisation Imager (3MI) is planned to fly on the Metop-SGA sat-ellites as part of the EUMETSAT Polar System – Second Generation (EPS-SG) programme in the timeframe beyond 2020. It is a radiometer dedicated to aerosol and cloud characterisation for cli-mate monitoring, atmospheric composition, air quality, and numerical weather prediction

This polarimetric mission is a heritage of the POLDER mission, with improved capabilities. The spectral range (12 channels) was extended from the visible–near-infrared (VIS-NIR) 410 to 910 nm) to the shortwave-infrared (SWIR) domain (up to 2200 nm). The spatial resolution (4 km at nadir) and the swath (2200×2200 km2) were also improved compared to previous POLDER instruments. As POLDER, 3MI will provide multi-polarisation (–60°, 0°, and +60°) and multi-angular (10 to 14 views) images of the Earth top of atmosphere outgoing radiance [1].

The POLDER heritage allows adapting techniques developed for PARASOL, e.g., for the vi-carious calibration methods. However the monitoring of the SWIR channels will be a new chal-lenge for the 3MI calibration. The access to a moon observation during commissioning would be very beneficial, in addition to the characterization of many other radiometric aspects. The 3MI will also strongly benefit from cross-calibration (radiometric, spectral, and geometric) with other Metop-SGA instruments like the VIS-IR Imager (METimage) and the ultraviolet–VIS-NIR-SWIR Sounder (Sentinel-5).

The level 1 products available to the users will be geolocated Stokes vectors on the native geometry (Level 1B) and geoprojected multi-directional and spectral Stokes vectors (Level 1C) [2]. Level-2 products will provide geophysical and microphysical parameters for aerosol and clouds. The presentation will overview the mission characteristics and the calibration strategy as well as the products available to the users. References [1] Fougnie, B., T. Marbach, A. Lacan, R. Lang, P. Schlüssel, G. Poli, R. Munro, and A. B. Couto, 2019:

The multi-viewing multi-channel multi-polarisation imager –Overview of the 3MI polarimetric mission for aerosol and cloud characterization. J. Quant. Spectrosc. Radiat. Transfer 219, 23–32.

[2] Lang, R., G. Poli, B. Fougnie, A. Lacan, T. Marbach, J. Riedi, P. Schlüssel, A. B. Couto, and R. Munro, 2019: The 3MI Level-1C geoprojected product –definition and processing description. J. Quant. Spec-trosc. Radiat. Transfer 225, 91–109.

Preferred mode of presentation: Oral

Numerical solution for scattering, absorption, and emission by large cometary dust particles Johannes Markkanen* and Jessica Agarwal Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg, 37077 Göttingen, Germany *Presenting author ([emailprotected]) Remote light-scattering and thermal infrared observations of comet’s comae provide us with hints of physical properties of cometary dust particles such as size, shape, porosity, and composition. Interpretation of such observations requires accurate and efficient numerical methods and models. Unfortunately, the available numerical techniques are either too computer-intensive or introduce insufficient approximations. We present a self-consistent numerical solution for scattering and thermal emission problems by extending the recently introduced dense medium radiative transfer solution [1–4] to treat thermally excited radiation. Further, we combine the radiative heat transfer part to the conductive heat transfer equation by employing the finite-element method. The devel-oped method will be applied to interpret the visible and superheating phase functions of the coma of the comet 67P/Churyumov–Gerasimenko measured by the Rosetta Optical, Spectroscopic, and Infrared Remote Imaging System and the Rosetta Visible and Infrared Thermal Imaging Spec-trometer, respectively.

This research was funded by the ERC Starting Grant No 757390. References [1] Muinonen, K., J. Markkanen, T. Väisänen, J. Peltoniemi, and A. Penttilä, 2018: Multiple scattering of

light in dense discrete random media using incoherent interactions. Opt. Lett. 43, 683–686. [2] Markkanen, J., T. Väisänen, A. Penttilä, and K. Muinonen, 2018: Scattering and absorption in dense

discrete random media of irregular particles. Opt. Lett. 43, 2925–2978. [3] Väisänen, T., J. Markkanen, A. Penttilä, and K. Muinonen, 2019: Radiative transfer with reciprocal

transactions: Numerical method and its implementation. PloS ONE 14, e0210155. [4] Markkanen, J., J. Agarwal, T. Väisänen, A. Penttilä, and K. Muinonen, 2018: Interpretation of the phase

functions measured by the OSIRIS instrument for comet 67P/Churyumov–Gerasimenko. Astrophys. J. Lett. 868, L16.

Preferred mode of presentation: Oral

Surface composition of (4) Vesta by modelling light scattering Julia Martikainena,*, Timo Väisänena, Antti Penttiläa, and Karri Muinonena,b aDepartment of Physics, University of Helsinki, Finland bGeospatial Research Institute FGI, National Land Survey, Kirkkonummi, Finland

*Presenting author ([emailprotected]) Understanding light scattering on planetary surfaces is an open problem. Spectroscopic, photomet-ric, and polarimetric features depend strongly on a number of surface properties that can also be affected by space weathering. The surface composition of asteroids has been studied in numerous laboratory experiments and by using empirical models, such as the Hapke model [1], but never before using numerical simulations based on the first principles in light scattering.

We have recently developed a new simulation framework to model the spectroscopy, photom-etry, and polarimetry of planetary surfaces. This approach is used to study asteroid (4) Vesta. We combine approximate multiple scattering codes SIRIS4 [2–4] and RT-CB [5], and an exact multi-ple scattering code JVIE [6] that utilizes the volume-integral equation method to account for both the wavelength-scale particles and particles that are larger than the wavelength. With our model, we derive the complex refractive indices and particle size distribution of Vesta’s regolith, and thus explain the observed negative linear polarization, opposition effect, and spectral features in the UV-vis-NIR wavelength region. References [1] Hapke, B., 1993: Theory of Reflectance and Emittance Spectroscopy. Cambridge University Press,

Cambridge, UK. [2] Lindqvist, H., J. Martikainen, J. Rabina, A. Penttila, and K. Muinonen, 2018: Ray optics for absorbing

particles with application to ice crystals at near-infrared wavelengths. J. Quant. Spectrosc. Radiat. Transfer 217, 329–337.

[3] Martikainen, J., A. Penttila, M. Gritsevich, and K. Muinonen, 2018: Spectral modeling of meteorites at UV-Vis-NIR wavelengths. J. Quant. Spectrosc. Radiat. Transfer 204, 144–151.

[4] Muinonen, K., T. Nousiainen, H. Lindqvist, O. Muñoz, and G. Videen, 2009: Light scattering by Gauss-ian particles with internal inclusions and roughened surfaces using ray optics. J. Quant. Spectrosc. Radiat. Transfer 110, 1628–1639.

[5] Muinonen, K., M. I. Mishchenko, J. M. Dlugach, E. Zubko, A. Penttilä, and G. Videen, 2012: Coherent backscattering verified numerically for a finite volume of spherical particles. Astrophys. J. 760, 118.

[6] Markkanen, J., 2013: Integral equation methods for extreme-parameter material and novel boundary conditions (PhD thesis, Aalto University).

Preferred mode of presentation: Oral

The HARP polarimeter family and application to aerosol and cloud characterizations J. Vanderlei Martinsa,b, Xiaoguang Xua,*, Brent McBridea,b, Henrique M. J. Barbosac, Anin Puthukkudya,b, Noah Sienkiewiczb, and Lorraine Remer a aJoint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD,

USA bDepartment of Physics, University of Maryland Baltimore County, Baltimore, MD, USA cInstituto de Física, Universidade de São Paulo, São Paulo, Brazil *Presenting author ([emailprotected]) The Hyper-Angular Rainbow Polarimeter (HARP) instruments are designed at the University of Maryland Baltimore County to make multi-angular multispectral polarimetric measurements needed to characterize microphysical properties for aerosols and clouds (https://laco.umbc.edu) [1]. Currently, there are three polarimeters based on the HARP concept: AirHARP, HARP Cu-beSat, and HARP-2. AirHARP is an airborne prototype instrument, which has been deployed in the NASA Lake Michigan Ozone Study (LMOS) and Aerosol Characterization from Polarimeter and Lidar (ACEPOL) campaigns during 2017. HARP CubeSat is a NASA funded 3U-size satel-lite to be launched in 2019 and is planned for a one-year mission lifetime. HARP-2 is an im-proved copy of the HARP CubeSat polarimeter payload and will be equipped on the NASA Plankton, Aerosol, Cloud, Ocean Ecosystems (PACE) mission satellite [2]. Specifically, the HARP polarimeter family measures radiance and polarization at 60 scan angles in the 670-nm wavelength and at 20 (10 for HARP-2) scan angles in each of other three spectral bands (440, 550, and 870 nm). These instruments also feature a 94° cross-track field of view, allowing a wide spatial coverage. In this presentation, we will demonstrate the HARP observation concept with the AirHARP observations collected during the LMOS and ACEPOL campaigns. We will also present preliminary applications of the AirHARP Level-1 products for characterizing cloud drop-let size and aerosol microphysical properties. References [1] Dubovik, O., Z. Li, M. I. Mishchenko, et al., 2019: Polarimetric remote sensing of atmospheric aero-

sols: Instruments, methodologies, results, and perspectives. J. Quant. Spectrosc. Radiat. Transfer 224, 474–511.

[2] Remer L. A., K. Knobelspiesse, P. Zhai, et al., 2019. Retrieving aerosol characteristics from the PACE mission. Part 2: Multi-angle and polarimetry. Front. Earth Sci. (submitted).

Preferred mode of presentation: Oral

Light scattering studies at the El Paso del Norte Region in Texas Richard Medina

Lewis Clark State College, 500 8th Ave, Lewiston, ID 83501, USA ([emailprotected]) The light-scattering properties of mineral dust and soot particles in the El Paso-Juarez Airshed were analyzed using data from an acoustic extinctiometer and a laser particle counter in conjunc-tion with a non-spherical scattering model for polydisperse and randomly oriented particles, the T-matrix model. The data selected correspond to days exhibiting a mean relative humidity less than 20% to avoid effects of possible aerosol hygroscopic growth. The inter-comparison for the selected days of the extinction and scattering coefficients results obtained using the T-matrix and the laser particle counter, with those obtained from an acoustic extinctiometer at a wavelength of 0.87 μm shows good agreement. In addition, the single-scattering albedo for this region is analyzed for the selected days. The methodology developed in this work can be used as a diagnostic tool to char-acterize mineral dust and soot particles, and the results of this study will provide a better under-standing of the aerosol optical properties for the El Paso-Juarez Airshed. Preferred mode of presentation: Oral

Propagation of electromagnetic radiation in a slab waveguide with topological insulator walls T. M. Meloa,*, D. R.Vianab, W. A. Moura-Meloc, J. M. Fonsecac, and A. R. Pereirac aIFRJ-Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro, Av. Prefeito Botafogo,

Rio de Janeiro, RJ 27541030, Brazil bFaculdade de Viçosa, St. Gomes Barbosa 870, Minas Gerais, MG 36570101, Brazil cUFV-Universidade Federal de Viçosa, Departamento de Física, Viçosa, Minas Gerais, MG 36570000,

Brazil *Presenting author ([emailprotected]) The topological magnetoelectric effect emerges whenever time reverse symmetry is broken at the surface of three-dimensional topological insulators (3D TI, like , and compounds) in the long-wavelength regime of electromagnetic (EM) radiation [1]. As conse-quence, the EM response of 3D TIs is given in terms of fine structure constant due to the quan-tized Hall current excited on the 3D TI surface by a parallel electric field [2,3]. Among other consequences, when light is sent to a TI border, its behavior is deeply modified: for instance, light plane polarization is rotated by a universal angle leading to unusual Kerr/Faraday and EM scattering effects [4].

Here, we shall show that whenever light propagation is guided by 3D-TI walls, it experiences a cutoff frequency coming from topological grounds, , which is related to the penetration length of metallic surface states into the TI-bulk, . The scenario is such that lower frequencies, < , are reflected by the walls, while for > considerable part of the incident light pen-etrates into the TI-bulk making wave propagation throughout the waveguide deeply jeopardized. Our findings suggest that TI-made waveguides enable an estimate of the microscopic quantity, , by measuring the topological optical response carried out by the macroscopic signature of [5]. Furthermore, such topological stability can be useful in waveguides to propagate EM radia-tion in scattering light experiments and applications [6]. References [1] Ortmann, F., S. Roche, and S. O. Valenzuela, 2015: Topological Insulators: Fundamentals and Per-

spectives. Wiley, New York. [2] Chang, M.-C., and M.-F. Yang, 2009: Optical signature of topological insulators. Phys. Rev. B 80,

113304. [3] Martín-Ruiz, A., 2018: Magnetoelectric effect in cylindrical topological insulators. Phys. Rev. D 98,

056012. [4] Tse, W. K., and A. H. MacDonald, 2010: Giant magneto-optical Kerr effect and universal Faraday

effect in thin-films of topological insulators. Phys. Rev. Lett. 105, 057401. [5] Melo, T. M., D. R. Viana, et. al., 2016: Topological cutoff frequency in slab waveguide: penetration

length in topological insulators walls. Phys. Lett. A 380, 973–976. [6] Nesterenko, M. V., V. A. Katrich, et. al., 2012: Electromagnetic waves scattering and radiation by

vibrator-slot structure in a rectangular waveguide. Prog. Electromagn. Res. 24, 69–84. Preferred mode of presentation: Oral

A comprehensive analysis of aerosol property retrieval from the MicroNeph–GRASP system Alireza Moallemia,*, Robin L. Modinia, Tatsiana Lapyonokb, David Fuertesb,c, Anton Lopatinc, Gergely Dolgosd, Yevgeny Derimianb, Benjamin Torresb,c, Oleg Dubovikb,c, and Martin Gysel-Beera

aLaboratory of Atmospheric Chemistry, Paul Scherrer Institute, Forschungsstrasse 11, 5232 Villigen PSI, Switzerland

bLaboratoire d’Optique Amosphérique, Université de Lille, 59655 Villeneuve d’Ascq Cedex, France cGRASP-SAS, Remote sensing developments, Université de Lille, 59655 Villeneuve d’Ascq Cedex, France dMicos Engineering GmbH, Überland Str. 129, 8600 Dübendorf, Switzerland *Presenting author ([emailprotected]) The phase function (F11) and polarized phase function (F12) are important elements of the scatter-ing matrix that contain implicit information regarding aerosol microphysical properties such as the size distribution, refractive index, and shape. The F11 and F12 can be measured in situ with polar imaging nephelometry [1]. The microphysical properties of the aerosol being measured can be inferred from these data by employing aerosol retrieval algorithms such as the Generalized Re-trieval Algorithm of Surface and Aerosol Properties (GRASP) [2,3]. Recently, the development began on a miniature version of a polar imaging nephelometer called MicroNeph. The goal of this study is to test the GRASP algorithm on the MicroNeph data.

A thorough numerical analysis is conducted to investigate the retrieval of particle size distri-bution, refractive index and shape distribution) from the combined MicroNeph–GRASP system. For a number of aerosol models encompassing a variety of microphysical properties, MicroNeph measurements (F11 and F12 at three visible wavelength) are simulated with the GRASP forward model. The simulated results are subjected to synthetic error and instrument-related parameters such as measured wavelength and angular resolution are manipulated. These data are then intro-duced to the GRASP inverse model, and the quality of the retrieval is investigated. The role of a priori assumptions in the GRASP inverse model on the retrieval quality is also assessed for various parameters such as the spectral refractive index. Finally, it is planned to test the GRASP algorithm on real MicroNeph data using either well-defined aerosol samples or independent measurements of aerosol microphysical properties. References [1] Dolgos, G., and J. V. Martins, 2014: Polarized Imaging Nephelometer for in situ airborne measure-

ments of aerosol light scattering. Opt. Express 22, 21972–21990. [2] Espinosa, W. R. et al., 2017: Retrievals of aerosol optical and microphysical properties from Imaging

Polar Nephelometer scattering measurements. Atmos. Meas. Tech. 10, 811–824. [3] Dubovik, O., et al., 2014: GRASP: a versatile algorithm for characterizing the atmosphere. SPIE News-

room, Sep. 2014. Preferred mode of presentation: Oral

Self-organized micellae with UV-light triggered fluorescence turn-on

Alexander E. Moskalenskya,b,* and Aleksey Yu. Vorob’eva,c aNovosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia bVoevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090,

Novosibirsk, Russia cN. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, 9 Lavrentiev Ave., 630090,

Novosibirsk, Russia

*Presenting author ([emailprotected])

Particles with stimulus-responsive fluorescence are in demand for imaging and diagnostic appli-cations [1,2]. Different strategies have been employed to obtain such particles (micellae or lipo-somes). We report a novel approach based on fatty acids conjugated with a photolabile group, which self-organize into micellae in water. Under near-UV illumination the photolabile group dis-sociates and becomes fluorescent, accumulating inside the drops.

Our experiments showed the formation of micellae with sizes ranging from one to several tens of micrometers. Initially, particles were not visible under a microscope with a 450–490 nm exci-tation and >520 nm emission filters. Illumination with a 365 nm LED during 100 ms turned on the orange-colored emission of micellae. The signal was stable for at least an hour. Further UV illu-mination increased the fluorescence intensity and made even the smallest observed particles very bright. This effect may potentially be used in life sciences (e.g., to track movements of particles from the specific origin) because fatty acids represent a bio-friendly material.

The study was supported by Russian Science Foundation (Grant No. 18-15-00049).

References [1] Niko, Y., Y. Arntz, Y. Mely, G. Konishi, and A. S. Klymchenko, 2014: Disassembly-driven fluores-

cence turn-on of polymerized micelles by reductive stimuli in living cells. Chem. A 20, 16473–16477.[2] Shi, S., Y. Liu, Y. Chen, Z. Zhang, Y. Ding, Z. Wu, J. Yin, and L. Nie, 2016: Versatile pH-response

micelles with high cell-penetrating helical diblock copolymers for photoacoustic imaging guided syn-ergistic chemo-photothermal therapy. Theranostics 6, 2170–2182

Preferred mode of presentation: Oral/Poster

Scattering of light in planetary regoliths: theory, experiments, and applications Karri Muinonena,b*, Timo Väisänena, Julia Martikainena, Johannes Markkanenc,a, Antti Penttiläa, Maria Gritsevicha,d, Jouni Peltoniemib,a, Jürgen Blume, Joonas Herranena, Gorden Videenf,g, Göran Maconia, Petteri Helandera, Ari Salmia, Ivan Kassamakova, and Edward Haeggströma aDepartment of Physics, University of Helsinki, Finland bFinnish Geospatial Research Institute FGI, National Land Survey, Masala, Finland cMax Planck Institute for Solar System Research, Göttingen, Germany dInstitute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia eInstitut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig,

Braunschweig, Germany fSpace Science Institute, Boulder, Colorado, USA gArmy Research Laboratory, Adelphi, Maryland, USA *Presenting author ([emailprotected]) Theoretical, numerical, and experimental methods are presented for scattering of light in macro-scopic discrete random media of densely-packed microscopic particles. The theoretical and nu-merical methods constitute a framework of Radiative Transfer with Reciprocal Transactions (R2T2). The R2T2 framework entails Monte Carlo order-of-scattering tracing of interactions in the frequency space, assuming that the fundamental scatterers and absorbers are wavelength-scale vol-ume elements composed of large numbers of randomly distributed particles. The discrete random media are fully packed with the volume elements. For spherical and nonspherical particles, the interactions within the volume elements are computed exactly using the Superposition T-Matrix Method (STMM) and the Volume Integral Equation Method, respectively. For both particle types, the interactions between different volume elements are computed exactly using the STMM. As the tracing takes place within the discrete random media, incoherent electromagnetic fields are uti-lized, that is, the coherent field of the volume elements is removed from the interactions. The experimental methods are based on acoustic levitation of the samples for non-contact, non-destruc-tive scattering measurements. The levitation entails full ultrasonic control of the sample position and orientation, that is, six degrees of freedom. The light source is a laser-driven white-light source with a monochromator and polarizer. The detector is a mini-photomultiplier tube on a rotating wheel, equipped with polarizers. The R2T2 is validated using measurements for a mm-scale spher-ical sample of densely-packed spherical silica particles. After validation, the methods are applied to interpret astronomical observations for asteroid (4) Vesta and comet 67P/Churyumov–Gerasi-menko visited by the NASA Dawn mission and the ESA Rosetta mission, respectively. Preferred mode of presentation: Oral/Poster

Absorptance of densely packed particulate samples

Andrei E. Mukhanova,* and Dmitrii B. Rogozkina,b aDukhov Research Institute for Automatics, 22, Sushchevskaya Street, 127055 Moscow, Russia bNational Research Nuclear University “MEPhI”, 31 Kashirskoe Shosse, 115409 Moscow, Russia

*Presenting author ([emailprotected])

This presentation addresses the problem of light transport in a weakly absorbing powder medium. The individual particles of the medium are assumed to be large compared to the wavelength. Different values of the particle refractive index, in the range from 1.3 to 4.0, are used in the calculations. The results of ray tracing Monte Carlo simulations are presented for three models of absorption in the medium. We consider bulk absorption of radiation in the powder particles themselves, absorption in the spaces between the particles, and continuous absorption. The total absorptance and the depth dependence of the absorbed energy are calculated for all these cases. At rather great depths, the obtained results can be fitted by the diffusion law with appropriate values of the absorption and transport mean free path. The value of the transport mean free path is retrieved by fitting the diffusion flux attenuation curve to the data of Monte Carlo simulations for the model of continuous absorption. The dependence of the ratio of the transport mean free path to the particle size on the filling factor of the powder medium and on the particle refractive index is studied. We find that, for given absorption and transport mean free path, the value of the energy absorbed in the sample depends on the model of absorption and differs from the corresponding prediction of the radiative transfer theory. The difference between the obtained results diminishes as the filling factor of the powder medium decreases. We propose a qualitative explanation of the observed effects, based on an analysis of the path distribution of photons in the medium and a comparison of the average photon paths inside and outside the particles.

The presented results can be useful for the management of absorption in various applications such as solar cells and other photovoltaic devices, absorption spectroscopy, and random lasers. See, e.g., [1–3].

References [1] Sgrignuoli, F., and P. Bettotti, 2016: Roughness-induced enhancement of optical absorption in random

media. J. Opt. Soc. Am. B 33, 915–921.[2] Koman V. B., Ch. Santschi, and O. J. F. Martin, 2016: Maximal absorption regime in random media.

Opt. Express 24, A1306–A1320.[3] Mupparapu R., K. Vynck, T. Svensson, et al., 2015: Path length enhancement in disordered media for

increased absorption. Opt. Express 23, A1472–A1484.

Preferred mode of presentation: Oral

Constraining aerosol vertical profile in the boundary layer using hyperspectral measurements of oxygen absorption

Vijay Natraja,*, Zhao-Cheng Zengb, Feng Xua, Thomas J. Pongettia, Run-Lie Shiab, Eric A. Kortc, Geoffrey C. Toona, Stanley P. Sandera, and Yuk L. Yungb aJet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA

91109, USA bDivision of Geological and Planetary Sciences, California Institute of Technology, 1200 East California

Blvd., Pasadena, CA 91125, USA cDepartment of Climate and Space Sciences and Engineering, University of Michigan, 500 South State

St., Ann Arbor, MI 48109, USA *Presenting author ([emailprotected])

Atmospheric aerosols have a major impact on climate, air quality and human health, and also in-fluence greenhouse gas retrievals from space by modifying the path of atmospheric radiation. However, uncertainties about the origin and composition of aerosol particles, their size distribu-tion, concentration, spatial and temporal variability make it challenging to characterize aerosols.

There are four ways to obtain aerosol information from passive remote sensing measurements: multi-angle, multi-wavelength, hyper-spectral and polarization measurements. Multi-angle meas-urements provide information on the aerosol single scattering albedo and phase function, while observations at multiple wavelengths provide extinction as a function of wavelength, and hence the loading and Ångström exponent. Together, they provide information on the aerosol loading and composition. Polarization measurements provide aerosol particle size, optical depth, and some information on speciation. They can also distinguish between spherical and non-spherical parti-cles. Further, they provide constraints to discriminate from the underlying surface. However, these measurements lack sensitivity to the vertical distribution of aerosols. On the other hand, hyper-spectral measurements in gaseous absorption bands (e.g. O2 A-, B- and γ-bands and H2O bands) can be used to characterize the vertical distribution of aerosol loading. This is because the large dynamic range of absorption in these bands allows different regions of the atmosphere to be probed at different absorption line strengths. Measurements in different bands also provide information on the wavelength dependence of aerosol extinction. Further, usage of O2 absorption has the ad-vantage that O2 is well mixed with known concentration. H2O, on the other hand, is variable, but has absorption features all across the electromagnetic spectrum.

We infer aerosol vertical structure in the urban boundary layer using passive hyperspectral measurements. Our algorithm, which uses hyperspectral measurements in the 1.27 μm oxygen absorption band to retrieve the total aerosol optical depth (AOD) and effective aerosol layer height, is applied to data from the California Laboratory for Atmospheric Remote Sensing instrument, located on a mountaintop overlooking the Los Angeles Basin. The effectiveness and accuracy of the retrievals are assessed by comparisons with AOD measurements from AERONET and aerosol backscatter profile measurements from a Mini MicroPulse Lidar lidar measurements. The pro-posed method can potentially be applied to existing and future satellite missions with hyperspectral oxygen measurements to constrain aerosol vertical distribution on a global scale.

Preferred mode of presentation: Oral

Multi-mode characterization of total columnar aerosols over China based on SONET ground-based remote sensing measurements since 2010

Yang Ou, Zhengqiang Li *, and Ying Zhang

State Environment Protection Key Laboratory of Satellite Remote Sensing, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China

*Presenting author ([emailprotected])

Aerosol is an important component of the terrestrial atmosphere and plays a key role in the deter-mination of global climate change, visibility, and human health. With the rapid development of the economy and human expansion, fine particulate matter is the most important air pollutant in many developing countries. However, the observation sites of Aerosol Robotic Network and Sky Radiometer Network are still very rare and are distributed unevenly over China. Sun-Sky Radi-ometer Observation Network (SONET, www.sonet.ac.cn) is a ground-based radiometer network with the extension of multiwavelength polarization measurement capability to provide long-term columnar atmospheric aerosol properties over China [1], which is a necessary remedy to an im-portant lack of total columnar atmospheric aerosols over China. There are 16 sites located in typ-ical regions of China, including urban, rural, desert, coastal, basin, mountain, and plateau areas, and the data have been obtained since 2010. The absolute aerosol optical thickness uncertainty can be less than about 0.01–0.02. In this study, we employ a new remote sensing method [2,3] to separate the characteristic peaks of atmospheric columnar aerosol volume particle size distribution (VPSD) and retrieve the complex refractive index (CRI) from the SONET observation over China from 2010–2016. It has been found that the aerosol VPSD can be decomposed into four character-istic peaks, including the fine, sub-fine (SF), sub-coarse (SC), and coarse modes, while CRIs can be separated into fine and coarse modes with CRI errors less than about 0.046 (real part) and 0.003 (imaginary part). The results show the mean central radii of the peaks in the fine, SF, SC, and coarse modes are around 0.15, 0.33, 1.86, and 3.30 μm, respectively. In general, the aerosols are complex and highly varying both in time and geographically. The SF mode is the major one in the eastern region in China. The absorption by aerosol in the eastern region is stronger than in the western region with the larger imaginary part of the CRI, while the scattering is weaker.

References [1] Li, Z. Q., H. Xu, K. T. Li, et al., 2018: Comprehensive study of optical, physical, chemical, and radia-

tive properties of total columnar atmospheric aerosols over China: an overview of Sun–sky radiometerObservation Network (SONET) measurements. Bull. Am. Meteorol. Soc. 99, 739–755.

[2] Zhang, Y. Z., Li, Y. Zhang, et al., 2016: Multi-peak accumulation and coarse modes observed fromAERONET retrieved aerosol volume size distribution in Beijing. Meteorol. Atmos. Phys. 128, 537–544.

[3] Zhang, Y., Z. Li, Y. Zhang, et al., 2017: Estimation of aerosol complex refractive indices for both fineand coarse modes simultaneously based on AERONET remote sensing products. Atmos. Meas.Tech. 10, 3203–3213.

Preferred mode of presentation: Poster

Demonstration of an overlap range of size parameters for reliable exact and approximate methods of computing single-particle scattering optical properties

R. Lee Panettaa,b*, Ping Yanga, Jiachen Dinga, Michael Mishchenkoc, and Siyao Zhaia

aDepartment of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA bDepartment of Mathematics, Texas A&M University, College Station, Texas, USA cNASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA

*Presenting author ([emailprotected])

Using any of several numerical methods based directly on Maxwell’s equations to calculate single particle scattering becomes increasingly demanding of computational resources as the size parameter of the particle increases, and as the particle’s index of refraction departs significantly from unity. With these so-called “exact” methods, at any given time there is an upper bound on the size parameter that is feasible for general and practical use, i.e., for “random orientation” calculations of particles that have arbitrary shapes and have indices of refraction that are not close to 1. The bound depends essentially on the state of hardware and software development at that time: beyond the size parameter bound exact methods may be used only under specializing assumptions like symmetry, or single-orientation, or index of refraction differing only slightly from unity. On the other hand, for large enough size parameters, numerical methods that are based on variously improved versions of geometrical and physical optics methods are adequate for computing single scattering properties of practical interest. These methods are not based directly on Maxwell’s equations but on physical approximations to the scattering process, and there is an effective lower bound on the size parameter for reliable calculations set by the physical approximations made.

Until recently there has been a gap in sizes between the upper bound of what can be feasibly handled handled by an exact method and the lower bound on what an approximate method can reliably treat. In this talk we describe success in closing the gap that has recently been achieved by using the exact Invariant Imbedding T-Matrix (II-TM) method in conjunction with an approximate Physical Geometric Optics Method (PGOM). The gap is closed in the sense that there is an overlap range of size parameters, roughly 100–300 in which the two methods agree well in their calculation of single-scattering optical properties. The II-TM method requires no special assumptions on particle symmetry, but it is possible to accelerate the computation of properties when some symmetries are present by improvements in the II-TM algorithm.

Preferred mode of presentation: Oral

Development of a flexible and fast Monte Carlo radiative transfer code for photon density wave spectroscopy

Christian Peest*, Oliver Reich, and Lena Bressel

University of Potsdam, Institute of Chemistry – Physical Chemistry / innoFSPEC, Am Mühlenberg 3, 14476 Potsdam, Germany

*Presenting author ([emailprotected])

Photon Density Wave (PDW) spectroscopy [1,2] is a measurement technique for the determination of the absorption coefficient and the reduced scattering coefficient of highly turbid samples [3]. It employs intensity modulated laser light in the MHz to GHz range, coupled into the sample via an optical fiber. The radiation forms a PDW which experiences a phase delay and a dampening in the turbid medium due to scattering and absorption. A receiving fiber feeds a detector attached to a network analyzer which measures the changes in amplitude and phase of the PDW depending on modulation frequency and fiber distance. and can be accurately determined via a nonlin-ear fit, even for highly turbid samples 0.1 mm < < 100 mm . This makes the PDW ide-ally suited for inline process analytics of large-scale industrial processes, e.g., paint, cosmetics or polymer production, without a need for sample dilution [4].

Theoretical considerations of the PDW necessarily make approximations in order to solve the related radiative transfer equations, such as the P1 approximation. Our group is exploring the limits of the PDW with respect to extremely high optical densities > 100mm , both through ad-vancements in theory and through experiments.

In this talk we present the development of a specialized Monte Carlo radiative transfer code for the simulation of PDW measurements. High optical depths ≫ 1000 require careful treat-ment and efficient speed-up procedures. We describe some of the techniques we employ, their adaptations to our specific system, and how they impact the simulations. Our code includes photon splitting, path length biasing, a modified random walk approach, parallelization and the peel-off mechanism.

References [1] Bressel, L., R. Hass, and O. Reich, 2013: Particle sizing in highly turbid dispersions by Photon Density

Wave spectroscopy. J. Quant. Spectrosc. Radiat. Transfer 126, 122–129.[2] Hass, R., M. Münzberg, L. Bressel, and O. Reich, 2013: Industrial applications of Photon Density Wave

spectroscopy for in-line particle sizing. Appl. Opt. 52, 1423–1431.[3] Münzberg, M., R. Hass, N. D. D. Khanh, and O. Reich, 2017: Limitations of turbidity process probes

and formazine as their calibration standard. Anal. Bioanal. Chem. 409, 719–728.[4] Hass, R., and O. Reich, 2011: Photon density wave spectroscopy for dilution-free sizing of highly con-

centrated nanoparticles during starved-feed polymerization. ChemPhysChem 12, 2572–2575.

Preferred mode of presentation: Oral

New desktop goniopolarimeter at FGI and joint measurement efforts

Jouni I. Peltoniemia,*, Nataliya Zubkoa, Juha Suomalainena, Teemu Hakalaa,Maria Gritsevichb,c, Lei Yand, Siyuan Liud, Zhongqiu Sune, and Jiao Zitif

aFinnish Geospatial Research Institute (FGI), Masala, FinlandbDepartment of Physics, University of Helsinki (UH), Finland cInstitute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia dPeking University, Beijing (PKU), China eNortheast Normal University (NENU), Changchun, Jilin, China fBeijing Normal University (BNU), China

*Presenting author ([emailprotected])

After hundreds of reflectance measurements with Finnish Geodetic Institute’s Field Goniospec-trometer (FIGIFIGO) [1], we are complementing our facility with a more precise desktop gonio-polarimeter. Field use requires many compromises that can be relaxed in laboratory, and some things are done in different way just to experiment and validate.

The new system is build around a central axis, where the spectrometer shelf, zenith arm, and sample tray on top are connected. It further differs from the old one by the main sensor ASD Field Spec 4 SR, 350–2500 nm (vs. Field Spec Pro FR), broad band wire grid polariser (vs. Glan-Thomas calcite prism), smaller field of view of 5 cm in diameter (vs. 20 cm), shorter arm length of 50–100 cm (vs. 150–250 cm), fully automatic movement (vs. manual azimuth). We further use a smaller 250 W QTH light source from Oriel (vs. 1000 W), with a beam width of 20 cm (vs. 60 cm), polarised using another wire grid (vs. unpolarised), three-lens setup (vs. two mir-rors).

First measurements agree within 5% with the FIGIFIGO and confirm there are no fundamen-tal flaws in either design. The new system has better polarisation accuracy, but the reflectance accuracy maybe even less, because of smaller signal after all the optics.

We are working together between FGI, UH, PKU, NENU, and BNU to cross-validate the po-larisation accuracy and to design measurement and illumination mechanics and optics further. We will present new results of sand, snow, dirt, and dirty snow. We compare the measurements against models developed in Finland, China, and elsewhere.

Reference [1] Peltoniemi, J. I., T. Hakala, J. Suomalainen, E. Honkavaara, L. Markelin, M. Gritsevich, J. Eskelinen,

P. Jaanson, and E. Ikonen, 2014: A detailed study for the provision of measurement uncertainty andtraceability for goniospectrometers. J. Quant. Spectrosc. Radiat. Transfer 146, 376–390.

Preferred mode of presentation: Oral/Poster

Space-weathering spectra explained with light scattering simulations A. Penttiläa,*, T. Väisänena, J. Markkanena,b, J. Martikainena, J. Escobar-Cerezoa, T. Kohoutc, G. Videend, and K. Muinonena,e aDepartment of Physics, University of Helsinki, Finland bMax Planck Institute for Solar System Research, Göttingen, Germany cDepartment of Geosciences and Geography, University of Helsinki, Finland dSpace Science Institute, Boulder, Colorado, USA eGeospatial Research Institute FGI, National Land Survey, Kirkkonummi, Finland *Presenting author ([emailprotected]) Space weathering (SW) of regolith particles on the surfaces of atmosphereless Solar System bodies is a mechanism that has been actively studied since the Apollo lunar samples (see, e.g., [1] and references therein). The mechanism has been verified in laboratory experiments and recently by studying samples from asteroid (25143) Itokawa by the Hayabusa mission [2]. It has been identi-fied that the spectral features associated with SW, namely the darkening and reddening of the spectra, are caused by nano- and microphase Fe inclusions in the thin rim of the regolith particles (see, e.g., [3]).

Until now, the physical first-principles model of the SW effects on spectra by Fe inclusions has been lacking. Extensive work has been done in this field using the Hapke model(s) (e.g., [4–6]), but the model only approximates radiative transfer treatment. One deficiency in the model is the lack of a proper treatment of the size effects of the Fe inclusions. Lucey and Riner [7] assessed this by including Mie scattering for the inclusions. However, current state-of-the-art modeling is missing a proper treatment of (i) surface reflections and volume scattering, and (ii) multiple scat-tering and incoherent fields associated with the inclusions.

We have recently completed a project aimed at improving the theory and computational tools for radiative transfer–type solutions in dense particulate media [8–10]. These are combined with our existing tools for light-scattering simulations with surface and volume scattering [11,12]. Us-ing these light-scattering simulation tools, we develop a detailed view on how the Fe inclusions affect the spectra of non-weathered silicate minerals. References [1] Hapke, B., 2001: J. Geophys. Res. 106, 10039–10073. [2] Matsumoto, T., et al., 2015: Icarus 257, 230–238. [3] Pieters, C. M., and S. K. Noble, 2016: J. Geophys. Res. Planets 121, 1865–1884. [4] Lawrence, S. J., and P. G. Lucey, 2007: J. Geophys. Res. 112, E07005. [5] Nimura, T., et al., 2008: Earth Planets Space 60, 271–275. [6] Vilas, F., and A. R. Hendrix, 2015: Astron. J. 150, 64. [7] Lucey, P. G., and M. A. Riner, 2011: Icarus 212, 451–462. [8] Muinonen, K., et al., 2018: Opt. Lett. 43, 683–686. [9] Markkanen, J., et al., 2018: Opt. Lett. 43, 2925–2928. [10] Väisänen, T., et al., 2019: PLOS One 14, e0210155. [11] Muinonen, K., et al., 2009: J. Quant. Spectrosc. Radiat. Transfer 110, 1628–1639. [12] Martikainen, J., et al., 2018: Mon. Not. R. Astron. Soc. 483, 1952–1956.

Preferred mode of presentation: Oral

Convolutional neural networks for aerosol scattering: the analogy to image recognition problems Patricio Piedra*, Aimable Kalume, Yong-Le Pan, and Gorden Videen

U.S. Army Research Laboratory, 2800 Powder Mill Rd., Adelphi, MD 20877, USA *Presenting author ([emailprotected]) Remote sensing of aerosol properties by inversion commonly requires directionally averaged aer-osol light-scattering shape models such as spheres or spheroids. However, using shape-averaged models often yields discrepancies in retrievals at different wavelengths, leading to inaccurate or at-best ambiguous aerosol classification. Furthermore, shape-averaging does not allow discrimi-nation of trace, non-averaged, scattering patterns. In our work, we have applied machine-learning algorithms to the calculated light-scattering patterns from particles of seven different, common, and naturally occurring shapes to test whether their shapes can be classified. Our dataset consists of either the scattering intensity distribution or the degree of linear polarization. Furthermore, our dataset was either one-dimensional, depending on the polar angle, or two-dimensional, depending on both the polar and azimuthal angles. The implementation of a one- or two-dimensional scatter-ing dataset input can be analogous to an image recognition problem, requiring either a fully con-nected or a convolutional neural network. Prediction capabilities were much greater when the two-dimensional scattering data was used than when only one-dimensional data were considered. When the two-dimensional intensity patterns are considered, the prediction capabilities were approxi-mately 70% for the regularly shaped particles and above 90% for the highly irregularly shaped particles. These capabilities increased slightly when linear polarization was used as input. These results suggest that trace-aerosol shape classification can be achieved using two-dimensional light-scattering patterns and convolutional neural networks.

This work has been funded by the U.S. National Academy of Sciences under National Research Council Postdoctoral Fellowship and by sponsorship from the U.S. Army Research Laboratory. Preferred mode of presentation: Oral

Electromagnetic scattering by heterogeneous anisotropic structure of high-order Bessel vortex beam

Tan Qua,*, Zhensen Wub,c, Qingchao Shangb, Jiaji Wua, and Zhengjun Lib aSchool of Electronic Engineering, Xidian University, Xi’an 710071, China bSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China cCollaborative Innovation Center of Information Sensing and Understanding, Xidian University,

Xi’an 710071, China

*Presenting author ([emailprotected])

Due to their wide applications in microwave technology, integrated optics, and sheath, anisotropic media have been researched extensively over the recent years. With the development of material and processing technology, various anisotropic materials with more complex structures and com-positions emerge. The scattering model of a hom*ogeneous anisotropic sphere is not suitable for the description of the problem anymore. In this paper, an analytical solution to the scattering by the heterogeneous anisotropic structure illuminated by a high-order Bessel vortex beam is investi-gated. By means of the Fourier transform and additional theorem, the internal fields of the hetero-geneous anisotropic-sphere periodic structure are expanded in terms of vector spherical wave func-tions. Combining this with the continuity boundary conditions for the tangential components of electromagnetic fields, the scattering coefficients of the heterogeneous anisotropic structure are solved. Compared with the results of the hom*ogeneous anisotropic sphere, the correctness of the theory and the code are verified. The scattering by heterogeneous anisotropic structures with dif-ferent compositions, structures, and numbers of particles are numerically analyzed. The orbital angular momentum spectrum of the scattered wave is presented to show the influence of the com-position on the phase distortion. The research will provide significant foundation for anisotropic materials and their optical properties.

Preferred mode of presentation: Oral

A practical way to detect and quantify the 3D radiative effects in passive cloud property retrievals: theoretical basis and feasibility study

Chamara Rajapakshe* and Zhibo Zhang

Physics Department, UMBC, Baltimore, Maryland, USA

*Presenting author ([emailprotected])

Most operational remote sensing algorithms are based on the computationally efficient 1D radia-tive transfer (RT) theory, while in reality, the RT process is intrinsically 3D. The 1D RT is based on two fundamental assumptions: the “plane parallel approximation” and “independent pixel ap-proximation”. When actual cloud fields deviate from these assumptions, the cloud radiative prop-erties derived from the 1D RT simulations will be different from the observed values, which is known as the “3D effects” in radiative transfer and cloud remote sensing. As a result, the retrieved cloud properties will be biased depending on the magnitude of the 3D effects and also on the retrieval technique. Take, for example, the bi-spectral cloud optical thickness (COT) and cloud-droplet effective radius (CER) retrieval. The so-called “illuminating effect” can lead to an overes-timation of the COT and underestimation of the CER, while the opposite shadowing effect leads to an underestimation of the COT and overestimation of the CER. Despite substantial efforts made in the past, there is still a lack of practical ways to detect and quantify the 3D effects at the pixel level.

Recently, we have developed a theoretical framework that uses a combination of polarimetric and radiometric measurements to detect the pixels of a radiometric image of clouds that are af-fected by the 3D radiative transfer effects. Moreover, with the aid of synthetic cloud fields from the large-eddy simulation model [1,2] and 3D radiative transfer simulations [3], we have success-fully demonstrated how the corrected radiances can significantly improve the statistics of cloud property retrievals.

References [1] Ackerman, A. S., M. P. Kirkpatrick, D. E. Stevens, and O. B. Toon, 2004: The impact of humidity

above stratiform clouds on indirect aerosol climate forcing. Nature 432, 1014–1017.[2] Zhang, Z., A. S. Ackerman, G. Feingold, S. Platnick, R. Pincus, and H. Xue, 2012: Effects of cloud

horizontal inhom*ogeneity and drizzle on remote sensing of cloud droplet effective radius: case studiesbased on large-eddy simulations. J. Geophys. Res. 117, D19208.

[3] Wang, Z., S. Cui, J. Yang, H. Gao, C. Liu, and Z. Zhang, 2017: A novel hybrid scattering order-de-pendent variance reduction method for Monte Carlo simulations of radiative transfer in cloudy atmos-phere. J. Quant. Spectrosc. Radiat. Transfer 189, 283–302.

Preferred mode of presentation: Oral/Poster

Decreasing trend of aerosol optical thickness associated with crop residue burning in Shangdong province observed from synthetic satellite data products

Kalluri Raja Obul Reddy, Xiaoyu Zhang*, and Lei Bi

School of Earth Sciences, Zhejiang University, Hangzhou 310027, China.

*Presenting author ([emailprotected])

Agriculture crop residue burning is an important source of aerosol pollutants. This presentation reports our study to obtaine the aerosol change trend associated with crop residue burning from synthetic satellite products. We focus on Shangdong province which is one of largest agricultural provinces in China. Specifically, we use Moderate Resolution Imaging Spectroradiometer AOT products, carbon monoxide (CO) product from the Measurements Of Pollution In The Troposphere, and fire pixel counts (derived from the active fire product) to evaluate the spatial and temporal variation of atmospheric aerosols during 2006 to 2017. First, a clear distinction of the AOTs was found in the two periods (2006–2011, and 2012–2017), with higher AOT in the first period, and weaker AOT in the second half period. Lower AOT in the second half period could be associated with tightening emission control policies. As an evidence, there has been a decrease in atmospheric loading for some anthropogenic aerosols over Shandong and neighboring provinces [1,2]. In addition to the AOT change, the spatial CO concentrations showed higher concentration (>200 ppbv) during 2006–2011 in the near surface level while lower concentrations (<200 ppbv) was observed during 2011–2017. This observation gives us confidence that the AOT change trend [3] was closely related to crop residue burning. Toward a better understanding of the various aerosol sources, we also report the isentropic back trajectory cluster analysis for the entire study period (2006–2017) by using the HYSPLIT model.

References [1] ChinaFAQs Project, 2012: China Adopts World-Class Pollutant Emissions Standards for Coal Power

Plants. http://www.chinafaqs.org/library/chinafaqschina-adopts-world-class-pollutant-emissions-standards-coal-power-plants.

[2] Xu, Y., 2011: Improvements in the operation of SO2 scrubbers in China’s coal power plants. Environ. Sci. Technol. 45, 380 –385.

[3] Xue, R., B. Ai, Y. Lin, B. Pang, and H. Shang, 2019: Spatial and temporal distribution of aerosol optical depth and its relationship with urbanization in Shandong Province. Atmosphere 10, 110.

Preferred mode of presentation: Poster

mailto:[emailprotected]

Assessing particle non-sphericity from the Fourier spectrum of its light-scattering pattern

Andrey V. Romanova,b,*, Valeri P. Maltseva,b,c, and Maxim A. Yurkina,b, aVoevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090, Novosibirsk, Russia bNovosibirsk State University, Pirogova Str. 2, 630090, Novosibirsk, Russia cNovosibirsk State Medical University, Krasny Prospect 52, 630091, Novosibirsk, Russia

*Presenting author ([emailprotected])

Measuring angle-resolved light-scattering patterns (LSPs) of single particles is a powerful approach for their non-invasive characterization. Because of the lack of a universal approach for solving the inverse light-scattering problem, each developed method adjusts to specific tasks and has its own advantages and disadvantages. Due to the wave nature of the studied physical phenomenon, spectral methods for solving inverse problems occupy a special niche, because they allow obtaining reliable results with minimal computational costs, are more resistant to various signal distortions, and afford an easy control of the solution process [1]. A separate issue for all methods is the potential deviation from the used shape model, incurring error in the retrieved particle characteristics. For example, it is difficult to reliably quantitatively describe deviation even from the simplest model of a hom*ogeneous sphere. A brute-force fit of an experimental LSP with the simulated ones can provide an estimation of non-sphericity only if an alternative shape model (e.g., a spheroid) is considered.

In this work, we enhanced the existing spectral method for solving the inverse light scattering problem for a sphere [1] to estimate the non-sphericity of a particle. As before we used the Fourier transformation of the LSP, but the amplitude spectrum only showed resistance to small deviations from sphericity, which is good for characterization, but bad for non-sphericity detection. Therefore, we used the full complex spectrum for a detailed assessment of non-sphericity. The method is based on quantitative comparison of the complex spectrum around the main peak with that corresponding to the effective sphere. The parameters of the latter are determined by the standard (amplitude) spectral method. Moreover, any other characterization method for spheres can be used, for example, non-linear regression applicable to any size and refractive index, but it might significantly increase the computation time.

We also introduced a quantitative definition of non-sphericity for a particle of arbitrary shape. Extensive simulations of LSPs were carried out for spheroids and red blood cells (RBCs). For the former we chose the non-sphericity parameter based on the analysis in the framework of Rayleigh-Gans-Debye approximation as the effective size times squared eccentricity. For the RBCs we applied geometrical fitting of the real shape by a sphere and defined general non-sphericity parameter as absolute volume discrepancy (residual) multiplied by the effective size.

The developed method was validated experimentally on the LSPs of milk fat globules and the red blood cells during spherization process, measured with the scanning flow cytometer. In particular, the RBCs do not seem to reach the ideal spherical shapes, which is either due to the hydrodynamic tensions in the flow or an artefact of the experimental distortions combined with high sensitivity of the method.

Reference [1] Romanov, A. V., A. I. Konokhova, E. S. Yastrebova, et al., 2017: Spectral solution of the inverse Mie

problem. J. Quant. Spectrosc. Radiat. Transfer 200, 280–294.

Preferred mode of presentation: Oral

Optical properties of oriented ice crystals and applications in lidar remote sensing and optical phenomenon simulations Masanori Saito and Ping Yang*

Department of Atmospheric Sciences, Texas A&M University, 3150 TAMU, College Station, TX 77843, USA

*Presenting author ([emailprotected]) Ice clouds are ubiquitous over the globe, and these clouds consist of various nonspherical ice crystals. Among these ice crystals, horizontally oriented hexagonal plates (HOPs) and columns (HOCs) have unique single-scattering properties such as extremely strong backscattering and angular scattering anisotropy about the scattering azimuth angle. These scattering properties sometimes cause specific optical phenomena in the sky. However, these horizontally oriented ice crystals have significant impacts on lidar measurements [1] and even non-negligible impacts on passive-satellite measurements under particular sun–view geometries [2]. Therefore, better quan-titative understanding of the single-scattering properties of horizontally oriented ice crystals is essential to take account of oriented ice crystals in the remote sensing of ice clouds. A recently developed physical-geometric optics method (PGOM) efficiently computes the single-scattering properties of ice crystals [3], which is fairly consistent with the counterparts computed with a rigorous computational technique, the invariant-imbedding T-matrix method (II-TM) [4].

This study develops a single-scattering property database of HOPs and HOCs in various sizes and incident angles at three wavelengths: 355, 532, and 1064 nm using PGOM. In the talk, we will demonstrate the single-scattering properties of a HOP and HOC, and their applications to the simulations of lidar signals and optical phenomena. References [1] Zhou, C., P. Yang, A. E. Dessler, Y. Hu, and B. A. Baum, 2012: Study of horizontally oriented ice

crystals with CALIPSO observations and comparison with Monte Carlo radiative transfer simula-tions. J. Appl. Meteorol. Climatol. 51, 1426–1439.

[2] Marshak, A., T. Varnai, A. and Kostinski, 2017: Terrestrial glint seen from deep space: oriented ice crystals detected from the Lagrangian point. Geophys. Res. Lett. 44, 5197–5202.

[3] Sun, B., P. Yang, G. W. Kattawar, X. Zhang, 2017: Physical-geometric optics method for large size faceted particles. Opt. Express 25, 24044–24060.

[4] Bi, L. P. Yang, G. W. Kattawar, and M. I. Mishchenko, 2013: Efficient implementation of the invari-ant imbedding T-matrix method and the separation of variables method applied to large nonspherical inhom*ogeneous particles, J. Quant. Spectrosc. Radiat. Transfer 116, 169–183.

Preferred mode of presentation: Oral

Far-infrared measurements benefit nighttime ice cloud property retrievals Masanori Saito* and Ping Yang

Department of Atmospheric Sciences, Texas A&M University, 3150 TAMU, College Station, TX 77843, USA

*Presenting author ([emailprotected]) Ice clouds are ubiquitous and play a pivotal role in the earth–atmosphere system. Satellite meas-urements have provided the global distribution of ice cloud properties based on passive remote sensing techniques. In particular, the bispectral method based on a pair of visible and near-infrared channels [1] and the split-window method based on the brightness temperature differences be-tween a pair of thermal infrared (TIR) channels (so-called window channels) [2] are the two major retrieval techniques. However, the former approach is not applicable during nighttime, and the latter approach is only sensitive to optically thin clouds with small ice crystals. Therefore, the current understanding of ice cloud properties is quite limited. Recently, a couple of projects focus-ing on spaceborne far-infrared (FIR) measurements are planned to understand outgoing FIR radi-ation from Earth. Although these projects do not mainly focus on ice clouds, previous studies demonstrate large sensitivities of FIR measurements to ice cloud properties [3]. This may over-come the shortcomings of the passive cloud remote sensing over nighttime. Therefore, there is a pressing need for quantitative evaluations of the feasibility and capability of the FIR measurements to ice cloud retrievals.

In this presentation, we quantitatively illustrate how much the FIR measurements, in addition to TIR, improve the ice cloud retrievals. Potential inherent error sources of ice cloud retrievals such as temperature-dependent indices of ice refraction and subpixel cloud coverage will be dis-cussed. References [1] Nakajima, T., and M. D. King, 1990: Development of optical thickness and effective particle radius of

clouds from reflected solar radiation measurements: Part I. Theory. J. Atmos. Sci. 47, 1878–1893. [2] Inoue, T. (1987), A cloud type classification with NOAA 7 split-window measurements, J. Geophys.

Res. 92, 3991–4000. [3] Yang, P., M. G. Mlynczak, H. Wei, D. P. Kratz, B. A. Baum, Y. X. Hu, W. J. Wiscombe, A. Heidinger,

and M. I. Mishchenko, 2003: Spectral signature of ice clouds in the far-infrared region: Single-scatter-ing calculations and radiative sensitivity study, J. Geophys. Res. 108, 4569.

Preferred mode of presentation: Oral

Analysis of self-regulated processes in optical fields E. Saldivia-Gomez*, A. Garcia-Guzman, and G. Martinez-Niconoff

Optics Department, Instituto Nacional de Astrofísica Óptica y Electrónica Luis Enrique Erro 1, Tonanzintla, Puebla, 72840, México

*Presenting author ([emailprotected]) In this work we analyze the evolution of a wave process and describe the synthesis of non-linear effects, by the study of the topological properties and the wave-diffusion transitions effects [1] of the optical field, which induce self- regulated effects; this kind of effects are present near of regions of maxim energy.

In this context the optical field is described as a complex system that presents an asymptotic behavior near the maxim irradiance region which generates entropy effects.

The study is made by the phase function [2] and irradiance driven by a logistic model in the refractive index, which allows us to identify physical properties in regions where singularities of the field exist and the traditional optical models cannot be applied.

With this model we want to explain how the focal regions interact, which explains the gener-ation of optical networks as the pool effect [2], and the generation of a beam rope in the vacuum through zone plates, which can be used to generate new ways of transmitting information. References [1] Martinez Niconoff, G., P. Martinez Vara, S. I. De los Santos Garcia, M. A. Torres-Rodriguez, M. Var-

gas Morales, and E. Saldivia Gomez, 2018: Analysis of wave-diffusion transitions in optical fields. J. Mod. Opt. 65, 2290–2294.

[2] Berry, M. V., 1980: Catastrophe optics: morphologies of caustics and their diffraction patterns. Prog. Opt. 18, 257–346.

Preferred mode of presentation: Poster

Light scattering by collections of metallic spheroids Dmitri Schebarchov, Walter R. C. Somerville*, Baptiste Auguié, and Eric C. Le Ru

The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600 Wellington, New Zealand

*Presenting author ([emailprotected]) Light scattering by nonspherical metallic nanoparticles supporting plasmon resonances is a cor-nerstone of surface-enhanced spectroscopies, but remains a challenging system to model theoreti-cally. Over the last several years we have extended the Extended Boundary-Condition Method for the specific case of spheroidal particles, as for this particular shape the T-matrix elements have unique numerical properties [1,2]. These investigations have resulted in an efficient and accurate numerical implementation for single spheroids [3], which enables benchmark calculations of far-field and near-field properties for a wide range of parameters. In particular, we used this method to demonstrate numerically the limits of the Rayleigh hypothesis, where the multipolar series ex-pansion of the scattered field may fail to converge in the vicinity of the particle [4].

Where light interacts with a collection of particles in relative proximity, multiple scattering effects can substantially affect the optical response. With the individual T-matrix of each scatterer already available, the superposition T-matrix framework is an appealing approach to describe the collective response of a cluster of such particles [5,6]. We have implemented several algorithms from the literature and compared their performance in the challenging case of light scattering by metallic spheroids. This contribution will present our results for different geometries of particle clusters, and notably discuss the convergence properties of far-field cross-sections and near fields when metallic spheroidal particles are placed such that their smallest circ*mscribing spheres in-tersect. References [1] Somerville, W. R. C., B. Auguié, and E. C. Le Ru, 2012: Severe loss of precision in calculations of T-

matrix integrals. J. Quant. Spectrosc. Radiat. Transfer 113, 524–535. [2] Somerville, W. R. C., B. Auguié, and E. C. Le Ru, 2015: Accurate and convergent T-matrix calculations

of light scattering by spheroids. J. Quant. Spectrosc. Radiat. Transfer 160, 29–35. [3] Somerville, W. R. C., B. Auguié, and E. C. Le Ru, 2016: SMARTIES: User-friendly codes for fast and

accurate calculations of light scattering by spheroids. J. Quant. Spectrosc. Radiat. Transfer 174, 39–55.

[4] Auguié, B., W. R. C. Somerville, S. Roache, and E. C. Le Ru, 2016: Numerical investigation of the Rayleigh hypothesis for electromagnetic scattering by a particle. J. Opt. 18, 075007.

[5] Mackowski, D. W., and M. I. Mishchenko, 1996: Calculation of the T matrix and the scattering matrix for ensembles of spheres. J. Opt. Soc. Am. A 13, 2266–2278.

[6] Stout, B., J. C. Auger, and A. Devilez, 2008: Recursive T matrix algorithm for resonant multiple scat-tering: applications to localized plasmon excitations. J. Opt. Soc. Am. A 25, 2549–2557.

Preferred mode of presentation: Oral

Bridging the knowledge gap between light scattering and microphysics on single atmospheric ice crystals

Franz M. Schnaitera,b,* and Emma P. Järvinenc aKarlsruhe Institute of Technology, Kaiserstraße 12, 76131 Karlsruhe, Germany bschnaiTEC GmbH, Oberes Buchenfeld 18, 77736 Zell a. H., Germany cNational Center for Atmospheric Research, 3090 Center Green Dr., Boulder, CO 80301, USA

*Presenting author ([emailprotected])

The interaction of shortwave solar radiation with ice particles is an important process in the at-mosphere which redistributes solar light on its way to the ground. Therefore, the knowledge of the angular light scattering behavior of atmospheric ice particles is crucial for a reliable calculation of the shortwave radiative transfer in climate models and for retrieving cloud bulk properties from satellites. Much of the current knowledge of the light scattering behavior of atmospheric ice parti-cles is gained from modelling studies, which apply optical models on simplified ice particle mor-phologies. Although these models have been significantly improved over the last decade, their results are still questionable especially when it comes to the effects of ice crystal complexity like hollowness and surface roughness. This is mainly because there are no in-situ measurements avail-able on single atmospheric ice particles that would allow for a validation from the perspective of fundamental single particle light scattering.

This lack of measurement data was the motivation to develop the Particle Habit Imaging and Polar Scattering (PHIPS) probe [1,2]. The PHIPS takes stereo microscopic bright field images of single atmospheric cloud particles and simultaneously acquires the correlated angular light scat-tering function. After the demonstration of its full functionality in 2017, the instrument participated in two campaigns targeting mixed-phase and pure ice clouds in high latitudes in 2017 and 2018. A unique and comprehensive data set of the microphysical properties and the correlated light scat-tering functions of real atmospheric ice particles is now available, and a catalog of individual ice crystals is currently being compiled that will be of high value for modelers developing and apply-ing single particle light scattering models.

In this presentation the PHIPS technology is introduced in detail, followed by an overview of the available single particle data set. First attempts of discussing some of the measured single crystal light scattering functions from a fundamental light scattering perspective are presented. The presentation concludes with an outlook for future instrument upgrades.

References [1] Abdelmonem, A., E. Järvinen, D. Duft, E. Hirst, S. Vogt, T. Leisner, and M. Schnaiter, 2016: PHIPS-

HALO: The airborne Particle Habit Imaging and Polar Scattering probe – Part 1: Design and operation.Atmos. Meas. Tech. 9, 3131–3144.

[2] Schnaiter, M., E. Järvinen, A. Abdelmonem, and T. Leisner, 2018: PHIPS-HALO: the airborne ParticleHabit Imaging and Polar Scattering probe – Part 2: Characterization and first results. Atmos. Meas.Tech. 11, 341–357.

Preferred mode of presentation: Oral

Scattering matrix of semi-infinite scattering media

Alexey A. Shcherbakov

ITMO University, 49 Kronverksky, 197101 Saint-Petersburg, Russia ([emailprotected])

Simulations of light scattering from strongly scattering media are important for many applications ranging from mineralogy to planetary science. When the refractive index contrast is sufficiently large, and the scale of inhom*ogeneities is comparable to the wavelength of the incident radiation, an accurate prediction of spectral angle-resolved reflection requires a rigorous numerical solution of Maxwell’s equations. A number of approaches dealing with this problem have been investi-gated, many of them analyzing bounded partitions of scattering media. Thus, often the transition from a single-scattering part to a semi-infinite bulk inhom*ogeneous material represents a consid-erable problem.

To cope with the problem we consider two approaches based on the Fourier space S-matrix methods for planar diffractive structures. A thick layer bounded by two planes is represented as an infinite crossed grating. When periods of such grating are taken to be sufficiently large in compar-ison with both the wavelength and the inhom*ogeneity scale, and the material and geometric com-position of each period corresponds to those of real media, an impact of the periodicity on the reflection characteristics can be made negligible. Simultaneously, this artificial periodicity allows us to apply analytically known S-matrix components of thin grating slices [1] and rigorously cal-culate the whole layer S-matrix.

As a first approach, the S-matrix composition algorithm can be used to repeatedly double S-matrix (and double the layer thickness respectively) until convergence of reflection parameters to a given accuracy. As a second approach, the Ambartsumian’s invariance principle developed within the radiative transfer theory [2,3] can be applied on the basis of ab initio S-matrix calcula-tions. The principle consisting in the invariance of reflective properties of a semi-infinite medium upon addition of a finite thickness layer yields a matrix Riccati equation. In this contribution, both theoretical formulations of the methods and analyses of their numerical behavior and bottlenecks will be discussed.

References [1] Shcherbakov, A. A., Yu. V. Stebunov, D. F. Baydin, et al., 2018: Direct S-matrix calculation for dif-

fractive structures and metasurfaces. Phys. Rev. E 97, 063301.[2] Ambartsumian, R., 1988: A life in Astrophysics. Selected Papers of V. A. Ambartsumian. Allerton Press,

New York.[3] Plass, G. N., G. W. Kattawar, F. E. Catchings, 1973: Matrix operator theory of radiative transfer. 1:

Rayleigh scattering. Appl. Opt. 12, 314–329.

Preferred mode of presentation: Oral

Features of spectral dependence of single-scattering characteristics for crystalline clouds Olga V. Shefer

National Research Tomsk Polytechnic University, School of Computer Science & Robotics, 30, Lenin ave., 634050, Tomsk, Russia

Presenting author ([emailprotected]) This work considers the extinction, scattering, and absorption coefficients and quantum survival probability as basic characteristics of single scattering. The physical optics method and the Mie theory are used to calculate these characteristics for individual particles of an ice cloud and for ensembles of crystals with various values of the particle aspect ratio and different parameters of the particle size distribution. The features of extinction, scattering, absorption, and single-scattering albedo are illustrated for various microphysical parameters of the crystal system at visible and infrared wavelengths. Particular attention is paid to the Christiansen spectral regions. According to the results of our numerical study, the most pronounced spectral dependences of the single-scattering characteristics are observed for a system of large predominantly oriented plates and wavelength-sized particles. The difference in their behavior is due to variations in the physicochemical properties of the particles even for identically shaped crystals. With the same concentration of the selected particles, the spectral dependence of the optical characteristics (e.g., extinction coefficient) for the large plates is more pronounced (by orders of magnitude) than for the small particles.

For a system of large translucent horizontally oriented plates, analytical expressions are presented to calculate the absorption and extinction coefficients. These expressions allow us to quantify the influence of microphysical parameters of the particles and their refractive index on the spectral dependence of the optical characteristics for a polydisperse medium containing large horizontally oriented plates with a minimal expenditure of computer resources. Preferred mode of presentation: Poster

Two dimensional shape retrieval from interferometric out-of-focus images of non-spherical particles

Huanhuan Shena,*, Lingyuan Wua, Yanglong Lia, and Weiping Wanga aInstitute of Fluid Physics, CAEP, 64 Mianshan road, Mianyang, 621999, China bKey Laboratory of Science and Technology on High Energy Laser, CAEP, Mianyang, 621999, China

*Presenting author ([emailprotected])

Interferometric out-of-focus images of non-spherical particles are commonly speckle-like patterns. We will present a treatment that is able to retrieve the two dimensional shape of the particle from its simulated interferometric out-of-focus image [1]. Firstly, the information retrieval issue from the interferometric out-of-focus image will be demonstrated identical to the phase retrieval under certain condition. Then the hybrid–input–output algorithm will be employed to conduct the recon-struction [2]. For a successful reconstruction, a tighter support is required. Thus, the method to get a tighter support will be explained. The reconstructed object has the same global two-dimensional shape of the real particle, though an ambiguity of the shape orientation exists. The size of the reconstructed image is scaled by the parameters for the reconstruction. After that, the superposed interferometric out-of-focus image of two single particles which are close enough to each other will be treated. We will show that the proposed treatment is capable to reconstruct the two particles at the same time. Finally, we will analysis the noise in the out-of-focus pattern that would hobble the reconstruction and thus advises will be given for optical system design. Moreover, preliminary experimental results will be presented.

References [1] Shen, H., L. Wu, Y. Li, and W. Wang, 2018: Two-dimensional shape retrieval from the interferometric

out-of-focus image of a nonspherical particle.—Part I: Theory. Appl. Opt. 57, 4968–4976.[2] Fienup, J. R., 1978: Reconstruction of an object from the modulus of its Fourier transform. Opt. Lett.

3, 27–29.

Preferred mode of presentation: Oral

Phase critical angle refractometry for nanoscale bubble growth measurement Lin Shia,*, Yingchun Wua, Xuecheng Wua, and Jianqi Shenb aState Key Laboratory of Clean Energy Utilization, Zhejiang University, 38 Zheda Rd., 310007

Hangzhou, China bUniversity of Shanghai for Science and Technology, 516 Jungong Rd., 200093 Shanghai, China *Presenting author ([emailprotected]) Bubbles exist in a wide range of natural systems and industrial processes [1]. Accurate measurements of bubble size and its transient growth are of great importance, which is able to characterize the interaction between bubbles and surroundings. Nanoscale growth of a micron-sized bubble is difficult to measure since it is beyond the resolution of current bubble sizing techniques [2–4]. In this talk we will present a newly developed phase critical angle refractometry (PCAR) technique for simultaneous size and growth measurement. First, the principle of PCAR was theoretically derived, which reveals that the phase shift of time resolved fine structure of bubble light scattering linearly correlated with bubble growth. Then we verified PCAR through the simulation of bubbles with tiny size change, and the accuracy was analyzed. At last, experiments on a single bubble with tiny bubble growth show the feasibility of PCAR technique. PCAR is a promising tool for bubble study and can be extended to industrially-relevant applications. References [1] Onofri, F.R.A., M. Krzysiek, J. Mroczka, et al., 2009: Optical characterization of bubbly flows with a

near-critical-angle scattering technique. Exp. Fluids 47, 721. [2] Onofri, F., 1999: Critical Angle Refractometry for Simultaneous Measurement of Particles in Flow:

Size and Relative Refractive Index. Part. Part. Syst. Charact. 16, 119–127. [3] Zhang, H., X. Wang, J. Sun, et al., 2018: Multidispersed bubble-size measurements by interferometric

particle imaging at scattering angles of 90° and 45°. Appl. Opt. 57, 10496–10504. [4] Lebrun, D., D. Allano, L., Méès et al., 2011: Size measurement of bubbles in a cavitation tunnel by

digital in-line holography. Appl. Opt. 50, H1–H9.

Preferred mode of presentation: Oral/Poster

Extinction efficiency calculation of an infinite multilayered cylinder using transmission coefficients

Nir Shiloaha,*, Moshe Kleimana, and Ioseph Gurwichb

aDeptartment of Applied Mathematics, Israel Institute for Biological Research, P.O.B. 19, Ness-Ziona, 7410001, Israel

bDeptartment of Electro-Optics, Ben-Gurion University, Beer-Sheva 8434231, Israel

*Presenting author ([emailprotected])

The purpose of this work is to develop a formalism for calculation of extinction efficiency, for infinite multilayer cylinder [1,2], based on the transmission coefficient.

We investigate particles with a large size parameter (the ratio between the particle size and wavelength) [3], and with high refractive index (optically non-soft particles, like metal-coated fi-bers).

The relationships are obtained by comparing the results of Mie calculations of the electromag-netic nearfield [4], with the classical theory of the electromagnetic field [5], and by using the fiber impedance parameter.

The mathematical expression obtained for the calculated transmission coefficient (and thus for the extinction efficiency) is quite complex, but it allows extraction of the extinction efficiency, which depends on the fiber parameters and its dielectric properties ( and ).

References

[1] Kleiman, M., I. Gurwich, and N. Shiloah, 2007: Enhanced extinction of electromagnetic radiation bymetal-coated fibers. J. Quant. Spectrosc. Radiat. Transfer 106, 184–191.

[2] Gurwich, I., N. Shiloah, and M. Kleiman, 1999: The recursive algorithm for electromagnetic scatteringby tilted infinite circular multilayered cylinder. J. Quant. Spectrosc. Radiat. Transfer 63, 217–229.

[3] Gurwich, I., N. Shiloah, and M. Kleiman, 2001: Calculations of the Mie scattering coefficients formulti-layered particles with large size parameters. J. Quant. Spectrosc. Radiat. Transfer 70, 433–440.

[4] Bohren, C. F., and D. R. Huffman, 1983: Absorbtion and Scattering of Light by Small Particles (Wiley,New-York).

[5] Lord Rayleigh, 1881: On the electromagnetic theory of light. Philos. Mag. 12, 81–101.

Preferred mode of presentation: Poster

Simulations of scattering by extremely oblate particles with the discrete dipole approximation D. A. Smuneva,* and М. А. Yurkinb,c aBelarusian State University, Nezavisimosti Av. 4, 220030 Minsk, Belarus bVoevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090,

Novosibirsk, Russia cNovosibirsk State University, Pirogova Str. 2, 630090, Novosibirsk, Russia

*Presenting author ([emailprotected])

The discrete dipole approximation (DDA) is a widely used method to simulate scattering and absorption of electromagnetic waves by particles of arbitrary shape and internal structure [1]. In most cases the DDA is used with a cubic lattice of dipoles, although theoretically dipoles (voxels) of any shape can be used, for example cuboid (rectangular parallelepiped). Still, the issues associated with the latter has been resolved only in 2015 [2]. Those “rectangular dipoles” allow significant reduction of computational time for some cases. Consider, for example, a graphene nanoplate with sizes 9 μm × 9 μm × 20 nm [2]. Dipole size has to be small to fit into the nanoplate thickness, which implies redundantly large number of dipoles to cover the width. By contrast, rectangular dipoles can be optimized for particular aspect ratios of the scatterer.

In this work we take the next step, by analyzing the rectangular-dipole formulation of the DDA in the limit of very small thicknesses of both dipole and scatterer. Taking the limit of zero thickness greatly simplifies the theoretical formulation, resulting in effectively 2D representation, where all optical quantities scale with various powers of particle thickness. It is equivalent to the Rayleigh–Debye–Gans approximation combined with the boundary conditions at the plane interface. We also proved that the scattering quantities computed with the standard (3D) code are independent of number of dipoles along the particle thickness, when the latter is sufficiently small.

Although the simulations based on the 2D theory are much faster than the standard DDA even for multi-layered structures (no linear system need to be solved), it can still be conveniently done within the framework of the DDA. Thus, we have implemented this capability as the development branch of ADDA: https://github.com/adda-team/adda/tree/2d_dda, as a natural extension of the existing command line options. After the simulation, ADDA generates standard output files, values in which are scaled to the corresponding powers of thickness. This can be used for various applications, including simulations of finite-width metasurfaces.

References [1] Yurkin, M. A., and A. G. Hoekstra, 2007: The discrete dipole approximation: an overview and recent

developments. J. Quant. Spectrosc. Radiat. Transfer 106, 558–89. [2] Smunev, D. A., P. C. Chaumet, and M. A. Yurkin, 2015: Rectangular dipoles in the discrete dipole

approximation J. Quant. Spectrosc. Radiat. Transfer 156, 67–79. Preferred mode of presentation: Oral

mailto:[emailprotected]

Optical force on a Mie particle by an Airy light-sheet using generalized Lorenz–Mie theory

Ningning Songa,*, Renxian Lia,b,**, Jiaming Zhanga, Shu Zhanga, Han Suna,and Bojian Weia aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an

710071, China

*Presenting author ([emailprotected])**Corresponding author ([emailprotected], [emailprotected])

Since Ashkin invented optical tweezers in 1986 [1], more and more scientists have been devoted to optical manipulation. The study of optical manipulation of micro- and nano-particles depends on specific light field. Traditional optical tweezers used Gaussian beam as trapping beam. In recent years, some new optical manipulation techniques based on novel laser beams have been developed. Airy light-sheet is a new type of optical field, and its amplitude distribution obeys the airy function. Airy light-sheet have self-healing [2], non-diffraction, self-acceleration [3], self-bending transmis-sion [4] and other excellent characteristics, and provides a possibility for the special and complex manipulation of light on particles. Exact prediction of optical force by laser beam is of practical significance for the development of novel optical tweezer systems.

Generalized Lorenz–Mie theory (GLMT) is an exact solution of the Maxwell equations, and can rigorously predict the optical force on a hom*ogeneous spherical particle induced by laser beams [5]. In this paper, the GLMT is employed to rigorously calculate optical force exerted on a sphere in the Mie regime induced by an Airy light-sheet. The results are of great significance for the development of Airy sheet based optical manipulation technology, and have potential applica-tions in the fields including single-molecule research, living cell research, high-precision meas-urement, etc. [6].

References [1] Ashkin, A., 1986: Observation of a single-beam gradient force optical trap for dielectric particles. Opt.

Lett. 11, 288–290.[2] Broky, J., G. A. Siviloglou, A. Dogariu, and D. N. Christodoulides, 2008: Self-healing properties of

optical Airy beams. Opt. Express 16, 12880–12891.[3] Siviloglou, G., J. Broky, A. Dogariu, and D. Christodoulides, 2007: Observation of accelerating Airy

beams. Phys. Rev. Lett. 99, 213901.[4] Dolev, I., T. Ellenbogen, N. Voloch-Bloch, et al., 2009: Control of free space propagation of Airy

beams generated by quadratic nonlinear photonic crystals. Appl. Phys. Lett. 95, 201112.[5] Gouesbet, G., and G. Grehan, 1982: A generalized Lorenz–Mie theory. J. Opt. 13, 97–103.[6] Dienerowitz, M., 2008: Optical manipulation of nanoparticles: a review. J. Nanophoton. 2, 021875.

Preferred mode of presentation: Oral

Sensitivity of aerosol refractive index to particle composition and component index uncertainties

Patrick G. Stegmanna,b*, Benjamin T. Johnsona,b, and Ping Yangc

aNOAA Center for Weather and Climate Prediction, 5830 University Research Ct., College Park, MD 20740, USA

bJoint Center for Satellite Data Assimilation cDepartment of Atmospheric Science, Texas A&M University, College Station, TX 77840, USA

*Presenting author ([emailprotected])

Stegmann and Yang [1] developed a novel, comprehensive refractive index database for dust aer-osol species. This database accounts for various dust compositions, including silicates, quartz, car-bonates, sulfates, soot (black carbon), and iron oxides. The database was compiled from multiple sources to cover a spectral range from 0.1 to 150 μm and beyond for specific individual species. Furthermore, the database also provides a software tool to compute the Bruggeman effective me-dium refractive index [2] of an arbitrary mixture of the components for real-world remote sensing applications. This is achieved through an invariant-imbedding-like approach that not only fur-nishes a unique solution for the effective index, but also allows to study the sensitivity of the Bruggeman effective medium to its input parameters in a rigorous manner. Similarly, Jacobian and adjoint equations for data assimilation applications can be formulated analytically. While slightly more involved than the traditional weighted summation approach, the proposed method thus offers distinct advantages. In addition to the database itself, the provided code is also available as an open source under the GPL v3.0 and can be cloned from its online repository [3].

In this talk we summarize the development and extent of the aerosol refractive index database, discuss the approach towards finding a unique solution for a Bruggeman effective medium, and provide sample results to illustrate the sensitivity of the effective refractive index to uncertainties in its composition and input component refractive indices.

References [1] Stegmann, P. G., and P. Yang, 2017: A regional, size-dependent, and causal effective medium model

for Asian and Saharan mineral dust refractive index spectra. J. Aerosol Sci. 114, 327–341.[2] Bruggeman, D. A. G., 1935: Calculation of various physical constants of heterogeneous substances: 1.

Dielectric permittivities and heat conductivities of mixed bodies made out of isotropic substances. Ann.Phys. 5, 636–664.

[3] https://github.com/PStegmann/Bruggeman_Effective_Medium

Preferred mode of presentation: Oral

Fast vector radiative transfer solution using improved small-angle approximation

Bingqiang Sun

Department of Atmospheric and Oceanic Sciences/Institute of Atmospheric Sciences, Fudan University, Shanghai, 200438, China ([emailprotected])

If the scattering phase matrix has a forward diffraction peak, an accurate solution of the corre-sponding vector radiative transfer equation is time-consuming. By decomposing the scattering phase matrix at certain scattering angles into the forward component and the remaining compo-nent, the original vector radiative transfer equation is decomposed into three equations: the forward equation, the regular equation, and the error equation. The forward equation is approximately solved using the small-angle approximation [1]. The regular equation is solved using the adding-doubling method. The error equation is described using the single-scattering approximation. The summation of the solutions from the three equations generates the final solution of the original radiative transfer equation. Using this decomposition, the vector radiative transfer equations with respect to an arbitrary scattering phase matrix can be rapidly but accurately solved. The computa-tional time is significantly reduced because the most time-consuming forward equation is solved by an analytic formula after using the small-angle approximation. The solution is verified against benchmarks and several applications are also shown in this presentation.

Reference [1] Sun, B., G. W. Kattawar, P. Yang, and E. Mlawer, 2017: An improved small-angle approxi-

mation for forward scattering and its use in a fast two-component radiative transfer method. J.Atmo. Sci. 74, 1959–1987.

Preferred mode of presentation: Poster

Resonance scattering by a dielectric sphere of a vector Airy beam

Han Suna,*, Renxian Lia,b,**, Jiaming Zhanga, Ningning Songa, Shu Zhanga,and Bojian Weia aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University,

Xi’an 710071, China

*Presenting author ([emailprotected] )**Corresponding author ([emailprotected])

Diffraction is one of the most important factors limiting the accuracy of instruments in optical systems. Since the concept of non-diffraction beams is put forward by Durnin [1], it has rapidly become a hot topic. An Airy beam, a novel non-diffraction beam, has some special characteristics such as self-recovery and self-bending. Resonance scattering analyses of Airy beams have some potential applications in optical manipulation, optical tweezers, imaging systems, and other fields.

In this paper, resonance scattering by a dielectric sphere illuminated by a vector Airy beam is investigated using the generalized Lorenz–Mie theory. A part of the non-resonant background is subtracted from the standard Mie scattering coefficients. Firstly, the electric fields of the vector Airy field is expressed using the angular spectrum decomposition [2]. The beam-shape coefficient is derived using multipole expansion of spherical harmonic functions. To further investigate the physical explanation of some special phenomena, the scattering coefficient of the dielectric sphere is expanded using Debye series [3]. The effects of parameters including the polarization, modula-tion parameter and transverse scale of Airy Beams are considered [4]. The advantage of the reso-nance method is that we can quantitatively describe the scattering using Debye series by separate diffraction effects from the external and internal reflections from the sphere.

References [1] Durnin, J., 1987: Exact solutions for nondiffracting beams (I): The scalar theory. J. Opt. Soc. Am. A 4,

651–654.[2] Caoa, Z., and C. Zhai, 2017: Angular scattering of an Airy beam light sheet by a concentric sphere. J.

Quant. Spectrosc. Radiat. Transfer 202, 31–36.[3] Gouesbet, G., 2003: Debye series formulation for Generalized Lorenz–Mie Theory with the Bromwich

method. Part. Part. Syst. Charact. 20, 382–386.[4] Mitri, F. G., R. X. Li, L. X. Guo, et al., 2015: Resonance scattering of a dielectric sphere illuminated

by electromagnetic Bessel non-diffracting (vortex) beams with arbitrary incidence and selective polar-izations. Ann. Phys. 361, 120–147.

Preferred mode of presentation: Oral

In situ measurement of vertical distribution of CO2 and CH4 in the troposphere by aircraft and tethered balloon Xiaoyu Suna, Minzheng Duana,*, Xiangao Xiaa, Disong Fua, and Zhongdong Yangb aInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China bNational Satellite Meteorological Center, CMA, Beijing, China *Presenting author ([emailprotected]) Several satellites have been launched into space to monitore the greenhouse gases concentration, by observing the backscattered hyper-spectral radiance in the SWIR, in the atmosphere therefore the vertical profile of greenhouse gases, especially carbon dioxide, and aerosol could greatly mod-ulate the retrievals. To investigate how the interplay process of the CO2 and aerosol scattering in the atmosphere, which is blamed for the uncertainty of the retrieval results of satellite measure-ments. Therefore, knowledge of CO2 vertical distribution is crucial for the development of satel-lite-borne retrieval methods and algorithm. Aircraft in situ measurements of carbon dioxide mixing ratio and methane over Jiansanjiang (46.77°N, 131.99°E) (August 2018) were conducted, and compared to the retrieval results of Orbiting Carbon Observatory 2 (OCO-2) and Chinese Carbon Dioxide Observation Satellite (TanSat). The aircraft measurements were carried out between alti-tudes of 0.6 to 7 km, and obtained vertical profile of CO2 and CH4 by an Ultra-Portable Greenhouse Gas Analyzer (Los Gatos Research, LGR). A constant increase of an averaged 15.26 ppm in CO2

mixing ratio were observed between altitude 2 to 7 km during the flight period. The methane meas-urements shows an averaged 0.5 ppm in CH4 mixing ratio increased below 2.0 to 0.6 km caused by the large emission from wide range paddy field below, and the mixing ratio above 2 km varies between 1.951 to 1.976 ppm without large mutation.

Another vertical profile measurements of CO2 and CH4 on tether-balloon platform was con-ducted on Changshou (107.00°E, 29.84°N) (January 2019). In this study, vertical profiles of CO2 mixing ratio measurements was made at low troposphere within altitude 0 to 1000 km. A strong vertical mixture of CO2 was observed between 0 to 700 km, and most profiles presents declining trends of CO2 and CH4 mixing ratio with the increase of altitude, since the experiment site located in an industrial park with a large greenhouse gases emission source. The results would enhance the understanding of the spatial variation of CO2 and CH4. Preferred mode of presentation: Poster

Improving the radiative transfer approximation in the geometric optics regime

Timo Väisänena,*, Julia Martikainena, Antti Penttiläa, and Karri Muinonena,b

aDepartment of Physics, University of Helsinki, Finland bFinnish Geospatial Research Institute FGI, National Land Survey, Kirkkonummi, Finland

*Presenting author ([emailprotected])

We have developed a set of light-scattering tools which can be used to model the spectroscopy, photometry, and polarimetry of planetary surfaces by linking the tools as a pipeline [1,2]. In these pipelines, scattering by densely packed media in the geometric optics regime is approximated by utilizing radiative transfer. A single diffuse scatterer is created by mixing light-scattering characteristics of individual particles statistically, which is then used as input in the SIRIS4 [2–4]. The problem is that the current approach neglects the so-called shadowing effect.

In order to study the effects of particles shadowing each other, we have developed a new version of the SIRIS which is capable of handling arbitrary geometries. Still, computing multiple scattering from millions of particles with multiple facets in the geometric optics regime is too computer-intensive, and hence we need to utilize our existing radiative transfer approach with possible corrections. We study approaches which might be used to improve the existing pipeline, such as using volume elements to replace the statistically diffuse scatterer or adding particles on top of the geometry containing diffuse scatterers.

References [1] Markkanen, J., J. Agarwal, T. Väisänen, A. Penttilä, and K. Muinonen, 2018: Interpretation of the phase

functions measured by the OSIRIS instrument for comet 67P/Churyumov–Gerasimenko. Astrophys. J.Lett. 868, L16.

[2] Martikainen, J., A. Penttilä, M. Gritsevich, and K. Muinonen, 2018: Spectral modeling of meteorites atUV-Vis-NIR wavelengths. J. Quant. Spectrosc. Radiat. Transfer 204, 144–151.

[3] Lindqvist, H., J. Martikainen, J. Räbinä, A. Penttilä, and K. Muinonen, 2018: Ray optics for absorbingparticles with application to ice crystals at near-infrared wavelengths. J. Quant. Spectrosc. Radiat.Transfer 217, 329–337.

[4] Muinonen, K., T. Nousiainen, H. Lindqvist, O. Muñoz, and G. Videen, 2009: Light scattering byGaussian particles with internal inclusions and roughened surfaces using ray optics. J. Quant.Spectrosc. Radiat. Transfer 110, 1628–1639.

Preferred mode of presentation: Oral

Location effects induced in moiré patterns with noise

M. Vargas Moralesa,*, G. Martinez Niconoffa, M. A. Torres Rodrigueza,and P. Martinez Varab,aINAOE Instituto Nacional de Astrofísica Óptica y Electrónica, optics department, Luis Enrique Erro 1,

Tonantzintla, Puebla, México Zip code 72840 bBUAP Benemérita Universidad Autónoma de Puebla, BUAP, Engineering faculty, Av. San Claudio,

Puebla, México *Presenting author ([emailprotected])

Strictly, all the physical systems present a certain degree of randomness characterized by the presence of noise. When a physical system is in competition with noise, the evolution of the system may induce/gener-ate novel physical properties, an example of this behavior being the generation of localization effects. Mechanism competition is suitably characterized by analyzing the correlation function, it means that the presence of noise generates directionality in the evolution of the physical processes. In this context we describe the evolution of periodical structures when they are perturbed with multiplicative noise. We show that increasing the random character, the structures generate localization when the correlation function takes the form of a decreasing exponential from the physical point of view. As a prototype, we use moiré struc-tures and this analysis is transferred to a plasmonic field propagating trough surface metal thin films. The propagation of plasmonic modes is generated by the coupling of the evanescent behavior.

References [1] McGurn, A. R., A. A. Maradudin, and V. Celli, 1985: Localization effects in the scattering of light from

a randomly rough grating. Phys. Rev. B 31, 4866–4871.[2] Mandel, L., and E. Wolf, 1995: Optical Coherence and Quantum Optics. Cambridge University Press,

Cambridge, UK.[3] Martinez Niconoff, G., M. A. Torres-Rodriguez, M. Vargas Morales, S. I. De Los Santos Garcia, P.

Martinez Vara, and A. Carbajal-Dominguez, 2017: Generation of long-range curved-surface plasmonicmodes and their propagation through thin metal films in a tandem array. Appl. Opt. 56, 8996–8999 .

Preferred mode of presentation: Oral/Poster

Doppler velocity comparison of cloud radar and Microrain radar

Xia Wana, Baike Xib,*, Guirong Xua, Chunguang Cuia, Linli Zhoua, and Zhikang Fua aInstitute of Heavy Rain, China Meteorological Administration, Hubei Key Laboratory for Heavy Rain

Monitoring and Warning Research, Wuhan 430074, China bDepartment of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA

*Presenting author ([emailprotected])

This study is trying to address that the uncertainty may be caused by the cloud radar Doppler velocity aliasing issue with the aid of Microrain radar and distrometer measurements. The Mesoscale Heavy Rain Observing System located at Xianning, Hubei province of China, provides a comprehensive measurement during Integrative Monsoon Frontal Rainfall Experiment (IMFRE) in the summer of 2018. Seven precipitation events during the IMFRE are selected under either convective or stratiform clouds except one event that includes both convective and stratiform rain periods. The data collected during this field champion allow us to investigate (1) the effectively of the existing dealiasing algorithm for cloud radar Doppler velocity; (2) the relationship between the Doppler velocities measured by cloud radar and the precipitation rate measured by the disdrometer. The algorithm is simplified and then applied to seven events of convective clouds and/or stratiform clouds in the campaign. MRR measured velocities are used as a criterion to validate the dealiasing velocities of cloud radar measured Doppler velocities under four different rain rate ranges. The multi-instrument measurements provide a verification for the dealiasing processing. Comparisons reveal cloud radar velocities agree well with MRR velocities under rain rate between 0 and 1mm/h with correlation coefficient of 0.98 and bias less than –0.3 m/s. For other three rain rate ranges, the agreements are also acceptable, therefore four linear fitting relationships between the dealias-ing Doppler velocities and the rain rate are proposed, respectively. Velocity vertical profiles of convective and stratiform clouds are also analyzed, and melting band is consistent with zero degree isotherm for stratiform clouds. At convective regions, the Doppler velocities are positively corre-lated with the precipitation rate, and the values increases while approaching the ground. At strati-form regions, very strong variation of Doppler velocities within the melting band, and the values are slightly deceasing with height except when the precipitation rate is greater than 10 mm/h.

References [1] Battaglia, A., E. Rustemeier, A. Tokay, C. Simmer, and U. Blahak, 2010: PARSIVEL snow observa-

tions: a critical assessment. J. Atmos. Oceanic Technol. 27, 333–344.[2] Guang, C. C., et al., 2015: The Mesoscale Heavy Rainfall Observing System (MHROS) over the middle

region of the Yangtze River in China. J. Geophys. Res. Atmos. 120, 10399–10417.[3] Clothiaux, E. E., T. P. Ackerman, G. G. Mace, K. P. Moran, R. T. Marchand, M. Miller, and B. E.

Martner, 2000: Objective determination of cloud heights and radar reflectivities using a combination of active remote sensor at the ARM CART sites. J. Appl. Meteorol. 39, 645–665.

[4] Fang, D., G. Liu, and X. Dong, 2007: The application of region growing in the analysis on velocity field of the weather. J. Nanjing Univ. (Nat. Sci.) 43, 625–632.

[5] Feng, Z., X. Dong, and B. Xi, 2011: A method to merge WSR-88D data with ARM SGP millimetercloud radar by studying deep convective systems. J. Atmos. Ocean. Technol. 26, 958–971.

Preferred mode of presentation: Poster

Optical properties of soot particles influenced by mixing structure Yuanyuan Wang and Weijun Li*

Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou, 310027, China

*Presenting author ([emailprotected]) Soot particles are ubiquitous in the atmosphere and have a strong absorption ability. Soot parti-cles tend to mix with other aerosol particles during ageing in the atmosphere. The aerosol parti-cles of different shapes and size mix with soot particles on various positions, which compromise different mixing structures. Many studies modeled and observed the optical properties of inter-nally mixed soot particles. Some numerical optical models such as the Rayleigh–Debye–Gans approximation, T-matrix, and Discrete Dipole Approximation have been used to simulate the op-tical properties of soot particles. Besides, some experimental methods such as a combination of the single-particle soot photometer and the three-wavelength photoacoustic soot spectrometer have been applied to characterize physicochemical properties of soot and measured their optical properties [1,2]. However, the calculated optical properties of soot particles are still rather incon-sistent with observed ones because of their complex shapes and mixing structures.

In this talk, we compare optical properties of soot particles with different mixing structures. We establish an improved internally mixed soot particles model with coatings of different shapes, numbers, and relative positions to soot particles according to their factual morphologies in the atmosphere. The improved atmospheric soot particle models show different optical properties with those in former works, which provide essential improvement to simulate optical properties of atmospheric internally mixed soot particles. References [1] Lan, Z.-J., X.-F. Huang, K.-Y. Yu, T.-L. Sun, L.-W. Zeng, and M. Hu, 2013: Light absorption of

black carbon aerosol and its enhancement by mixing state in an urban atmosphere in South China. Atmos. Environ. 69, 118–123.

[2] Liu, S., A. C. Aiken, K. Gorkowski, et al., 2015: Enhanced light absorption by mixed source black and brown carbon particles in UK winter. Nat. Commun. 6, 8435.

Preferred mode of presentation: Oral

Photonic jets generated by a spherical particle excited by a shaped beam Jiajie Wang*, Le Zhu, and Yiping Han

School of Physics and Optoelectronic Engineering, Xidian University, 710071, China *Presenting author ([emailprotected]) Photonic jets (PJs) are narrow and elongated spots which have a subwavelength beam waist and propagate with little divergence for several wavelengths. The feasibility of using a photonic jet to design super-resolution optical microscopy [1], tools for precision cell surgery and tumor detection [2], applications in optical tweezers [3] as well as to develop optical data storage devices with ultrahigh density of information recording and technologies of direct write nano-patterning [4] makes the photonic jet a hot research spot in recent years.

The key parameters of PJs (transverse dimension, length, peak and intensity) formed in the vicinity of hom*ogeneous dielectric microspheres and microcylinders under exposure of plane wave radiation has been thoroughly studied. These studies have shown that both the PJs shape and in-tensity depend significantly on the size and optical properties of a generating particle. However, there is limited studies on the investigation of the properties of a PJ excited by a shaped beam. As we realized that by the use of sharply focused laser beams or structured beams, where additional localization of a photonic stream and its effective volume reduction can be achieved, the properties of a PJ would be changed and some features will be enhanced.

In this talk we will report our recent work on the investigation of PJ generated by spherical particles excited by shaped beams. The tunable of PJs parameters brought by structured beams, including Bessel beam, Gaussian beam, and by properties of particles are discussed. Numerical results concerning the position of maximal intensity, longitudinal and transversal dimensions of the PJs, and its peak intensity will be presented. References [1] Hao, X., C. Kuang, X. Liu, H. Zhang, and Y. Li, 2011: Microsphere based microscope with optical

super-resolution capability. Appl. Phys. Lett. 99, 203102. [2] Seidfaraji, H., M. Hasan, and J. J. Simpson, 2012: A feasibility study of microjets applied to breast

cancer detection. Proc. 2012 Int. Conf. Electromagn. Adv. Appl., 949–951. [3] Yannopapas, V., 2012: Photonic nanojets as three-dimensional optical atom traps: a theoretical study.

Opt. Commun. 285, 2952–2955. [4] Kong, S.-C., A. Sahakian, A. Taflove, and V. Backman, 2008: Photonic nanojet-enabled optical data

storage. Opt. Express 16, 13713–13719.

Preferred mode of presentation: Oral

Properties of aerosols and clouds from lidar and radar soundings: experiment and theory

Zhenzhu Wanga,*, Dong Liua, Anatoli Borovoib, Chenbo Xiea, and Yingjian Wanga aKey Laboratory of Atmospheric Optics, Anhui Institute of Optics and Fine Mechanics, Chinese Academy

of Sciences, Hefei 230031, China bV. E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk,

634055, Russia

*Presenting author ([emailprotected])

Aerosols play important roles in environmental quality and sometimes cause serious problems such as endangering human health and reducing visibility. Furthermore, aerosols directly affect the earth’s radiation balance through scattering and absorbing solar radiation, and they indirectly influence the properties and lifetimes of clouds by acting as a condensation nucleus or an ice nu-cleus in cloud formation, eventually influencing the global climate change. At the meanwhile, Clouds strongly regulate radiative transfer and the hydrological cycle, which are important parts of Earth's weather and climate. The optical characteristics of aerosol and cloud are poorly studied yet because of the strong spatial and temporal variability of them. A lidar and a radar are two common useful tools for aerosol and cloud, which can provide the possibility to retrieve the verti-cal profiles of both the number density of particles and their microphysical characteristics, in com-parison with the passive remote sensing methods. In this study, a multi-wavelength Raman–Mie lidar, a CCD lidar, and a 35-Ghz radar are employed to measure the properties of aerosols and clouds. The extinction at 0.355 and 0.532 μm and backscattering at 0.355, 0.532, and 1.064 μm coefficients and the phase function at 0.532 μm from lidar, and the effective reflectivity factor from radar are inversed for use. Furthermore, the quantities responsible for microphysics can be extracted and explained as the dimensionless values, such as the linear depolarization ratio, the color ratio, the lidar ratio and the other ratios. Then these microphysical properties for aerosol and cloud during campaigns are analyzed in detail.

Preferred mode of presentation: Oral

The effect of inhom*ogeneity of wet sea salt aerosols on direct radiative forcing Zheng Wanga,*, Lei Bia, Bingqi Yib, and Xiaoyu Zhangc aDepartment of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou, China bSchool of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and

Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China cSchool of Earth Sciences, Zhejiang University, Hangzhou, China *Presenting author ([emailprotected]) In a humid environment, wet sea salt aerosols are always considered to be spherical in most climate models. However, sea salt aerosols are inhom*ogeneous during hygroscopic processes (deliques-cence and crystallization). As relative humidity (RH) increases or decreases, sea salt particles are coated by water or crystallized in droplets. In this study, we used a two-layer sphere model to simulate optical properties of wet sea salt in specified ranges of RH. We have found that the asym-metry factor of coated sea salt is much lower than that of the volume equivalent hom*ogeneous spherical sea salt, indicating stronger backscattering of coated sea salt. To assess the impact of the aforementioned inhom*ogeneity on direct radiative forcing of sea salt aerosols, we used the Com-munity Earth System Model. Results show that on global scale the inhom*ogeneity of wet sea salt has limited effect on direct radiative forcing; however, over the coastal regions bias of direct radi-ative forcing between inhom*ogeneous and hom*ogeneous sea salt aerosols could be up to 10% [1]. From a remote sensing perspective, in coastal regions, both the nonsphericity and inhom*ogeneity should be considered to compute the optical properties of sea salt aerosols due to a large range of RH [2]. References [1] Wang, Z., L. Bi, B. Yi, and X. Zhang, 2019: How the inhom*ogeneity of wet sea salt aerosols affects

direct radiative forcing. Geophys. Res. Lett. 46, 1805–1813. [2] Bi, L., W. Lin, Z. Wang, X. Tang, X. Zhang, and B. Yi, 2018: Optical modeling of sea salt aerosols:

the effects of nonsphericity and inhom*ogeneity. J. Geophys. Res. Atmos. 123, 543–558. Preferred mode of presentation: Poster

Theoretical extension of universal forward and backward Monte Carlo radiative transfer modeling for passive and active polarization observation simulations

Zhen Wanga,*, Shengcheng Cuib, Zhibo Zhangc, Jun Yanga, Haiyang Gaoa,and Feng Zhangd aKey Laboratory for Aerosol–CloudPrecipitation of China Meteorological Administration, School of

Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044, China

bKey Laboratory of Atmospheric Optics, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China

cPhysics Department, University of Maryland, Baltimore County, Baltimore, MD 21250, USA dSchool of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing

210044, China

*Presenting author ([emailprotected])

The theoretical framework of universal forward and backward Monte Carlo radiative transfer mod-eling in [1] is extended for passive and active polarization observation simulations [2]. It is built upon newly derived forward and backward vector scattering order-dependent integral radiative transfer equations (IRTEs). The unified mathematical formalism not only establishes the design of object-oriented software architecture, but also speeds up software development via the reuse of developed scalar code. The polarization simulations are implemented with the addition of the Stokes vector and the Mueller matrix weight tracing schemes. To improve numerical performance order by order, the extension implementation of hybrid scattering order-dependent variance reduc-tion techniques are given detailedly, with a focus on the formulation of scattering phase matrix truncation on the basis of remodeling vector IRTEs. To enrich polarization simulation features, not only scattering operators but also source vector function and detector response matrix function are formulated in unified mathematical forms for the hierarchies organization of various atmos-phere, surface, source and detector classes. The framework was fully implemented in MSCART model. For passive simulation, it not only can handle all 1D and 3D test cases in Phases A and B of the IPRT intercomparison project using forward and backward algorithm, but also simulate polarized radiance in a specified direction at a specified position using backward algorithm. For active simulation, lidar backscatter range-resolved signals can be simulated using forward algo-rithm. The source package is freely available for research purpose from the corresponding author, with online documentation from https://intersharp.gitlab.io/mscart-docs.

References [1] Wang, Z., S. Cui, J. Yang, H. Gao, C. Liu, and Z. Zhang, 2017: A novel hybrid scattering order-de-

pendent variance reduction method for Monte Carlo simulations of radiative transfer in cloudy atmos-phere. J. Quant. Spectrosc. Radiat. Transfer. 189, 283–302.

[2] Wang, Z., S. Cui, Z. Zhang, J. Yang, H. Gao, and F. Zhang, 2019: Theoretical extension of universalforward and backward Monte Carlo radiative transfer modeling for passive and active polarization ob-servation simulations (submitted).

Preferred mode of presentation: Oral

Measuring formation of a vapor bubble around a heated nanoparticle and size of nanoparticles by holography Linglong Wang*, Yingchun Wu, and Xuecheng Wu

State Key Laboratory of Clean Energy Utilization, Zhejiang University, 38 Zheda Rd., 310007 Hangzhou, China *Presenting author ([emailprotected]) Nanoscale particles and micron-sized bubbles are widely found in many industrial processes. The properties exhibited by nanomaterials in the fields of chemical, medical, material and environment sciences are closely related to particle size [1]. When the laser is focused on liquids dispersed with nanoparticles, the formation of laser-induced bubbles are related to the size of particle [2–5]. In this talk we will present the recovery of the size of nanoparticle by measuring the growth process of the laser-induced bubble when the nanoparticles are dispersed in liquids and irradiated by a strong pulsed laser. First, vapor bubbles are formed due to photothermal conversion between laser pulses and liquids containing absorptive nanoparticles, and the growth process of induced bubbles (including expansion and contraction) is recorded by high-speed holography. Then a bubble growth model is established based on heat transfer and bubble dynamics for predicting the size change of bubble generated by the laser irradiation of the nanoparticle. Finally, the size of nano-particle is deduced and obtained from the experimentally measured bubble size and the numerical simulation results. The research result provides a method for measuring the size of nanoparticles and vapor bubble variation during liquid flow. References [1] Niskanen, I., V. Forsberg, D. Zakrisson, S. Reza, et al., 2019: Determination of nanoparticle size using

Rayleigh approximation and Mie theory. Chem. Eng. Sci. 201, 222–229. [2] Lapotko, D., and E. Lukianova, 2005: Laser-induced micro-bubbles in cells. Int. J. Heat Mass Trans-

fer 48, 227–234. [3] Baffou, G., J. Polleux, H. Rigneault, and S. Monneret, 2014: Super-heating and micro-bubble genera-

tion around plasmonic nanoparticles under CW illumination. J. Phys. Chem. C 118, 4890–4898. [4] Wang, Y., M. E. Zaytsev, H. L. The, et al., 2017: Vapor and gas-bubble growth dynamics around laser-

irradiated, water-immersed plasmonic nanoparticles. ACS Nano 11, 2045–2051. [5] Angelsky, O. V., A. Y. Bekshaev, P. P. Maksimyak, et al., 2017: Controllable generation and manipu-

lation of micro-bubbles in water with absorptive colloid particles by CW laser radiation. Opt. Ex-press, 25, 5232–5243.

Preferred mode of presentation: Oral

Vector radiative transfer properties of inhom*ogeneous ice clouds in spherical atmosphere

Mingjun Wang*, Jihua Yu, Xizheng Ke, and Leili Guo

School of Automation and Information Engineering, Xi’an University of Technology, 710048 Xi’an, China

*Presenting author ([emailprotected])

Clouds composed of ice crystals are an important part of the atmosphere [1–3]. Research on at-mospheric radiative transfer properties under an ice cloud condition is helpful to understand the role of ice clouds on remote sensing, atmospheric detection, and many other fields in atmospher-ic physics. However, the study of radiative transfer properties involving ice clouds have often been based on the assumption that the atmosphere is plane parallel [4–5]. Because of the influ-ence of a spherical atmosphere, this assumption is no longer valid when the solar zenith angle is greater than 70° [6].

Our presentation will compare the vector radiative transfer properties of inhom*ogeneous ice clouds in plane parallel and spherical atmospheres at 1.55μm. Changes in the ice cloud transmit-tance and reflectance with effective radius, ice water content, relative azimuth angle, cloud bot-tom height, and so on will be computed numerically and analyzed in the case of a spherical at-mosphere. The effect of ice particle shapes and degrees of roughness on radiative transfer prop-erties will be also analyzed and compared. This research will provide theoretical support for sat-ellite-to-ground laser communication, satellite remote sensing, and other engineering applica-tions.

This work is partly supported by the National Natural Science Foundation of China (Grant No. 61771385) and the Key industry innovation chain of Shaanxi Province (Grant No. 2017ZDCXL-GY-06-01).

References [1] Yang, P., K. N. Liou, L. Bi, et al., 2015: On the radiative properties of ice clouds: light scattering,

remote sensing, and radiation parameterization. Adv. Atmos. Sci. 32, 32–63.[2] Liou, K. N., and P. Yang, 2016: Light Scattering by Ice Crystals: Fundamentals and Application.

Cambridge University Press, Cambridge, UK.[3] Yang, P., S. Hioki, M. Saito, et al., 2018: A review of ice cloud optical property models for passive

satellite remote sensing. Atmosphere 9, 499–529.[4] Mayer, B., and A. Kylling, 2005: The libRadtran software package for radiative transfer calculations

– description and examples of use. Atmos. Chem. Phys. 5, 1855–1877[5] Emde, C., R. Burasschnell, A. Kylling, et al., 2016: The libRadtran software package for radiative

transfer calculations (version 2.0.1). Geosci. Model Dev. 8, 10237–10303.[6] Emde, C., and B. Mayer, 2007: Simulation of solar radiation during a total eclipse: a challenge for

radiative transfer. Atmos. Chem. Phys. 7, 2259–2270.

Preferred mode of presentation: Poster/Oral

The turbulence influence on average intensity of Gaussian beams Wang WanJuna and Wu ZHenSena,b,* aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an, Shaanxi 710071, China bCollaborative Innovation Center of Information Sensing and Understanding at Xidian University, Xi’an,

Shaanxi 710071, China *Presenting author ([emailprotected]) As a basic beam, the Gaussian beam is widely studied for its simple form and applied in many areas, such as optical communications, laser radar, image analysis, and so on. It could also be used for comparison with other complex beams. In this paper, the average intensity of Gaussian beams is studied based on the Rytov theory, and the statistical moment of the turbulence phase perturba-tion is derived. Much work has been done by Andrews et al. [1,2], but some derivation process is not explained in detail [3]. In this paper, the work on the statistical moment of the turbulence is summarized and sorted out, the statistical moment of the turbulence is derived using Mathematica, and the final expression references that in [4]. An approximation that may cause a large bias is also pointed out. The final simple form of the polynomials is obtained by the hypergeometric func-tion approximation with the curve fit in Matlab. The expression of the statistical moment of the turbulence is divergent at a large beam radius caused by the approximation of the Rytov theory; a window function is proposed to limit the divergence at the beam edge. This work provides theo-retical basis for the application of the Gaussian beams. References [1] Andrews, L. C., and R. L. Phillips, 2005: Laser Beam Propagation Through Random Media. SPIE

Press, Bellingham, WA. [2] Miller, W. B., J. C. Ricklin, and L. C. Andrews, 1993: Log-amplitude variance and wave structure

function: a new perspective for Gaussian beams. J. Opt. Soc. Am. A 10, 661–672. [3] Miller, W. B., J. C. Ricklin, and L. C. Andrews, 1994: Effects of the refractive index spectral model on

the irradiance variance of a Gaussian beam. J. Opt. Soc. Am. A 11, 2719–2726. [4] Young, C. Y., and L. C. Andrews: Effects of a modified spectral model on the spatial coherence of a

laser beam. Waves Rand. Med. 4, 385–398. Preferred mode of presentation: Oral/Poster

Generation of Airy beam using optical antenna

Bojian Weia,*, Renxian Lia,b,**, Jiaming Zhanga, Shu Zhanga, Ningning Songa,and Han Suna aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University,

Xi’an 710071, China

*Presenting author ([emailprotected])**Corresponding author ([emailprotected], [emailprotected])

In recent years, nanoantennas have had broad applications, such as super-resolution near-field mi-croscopy imaging, high-efficiency solar cells, and nanolithography. Nanoantennas can efficiently collect light energy and confine it to a subwavelength volume, and their basic principle is surface plasmon polarition resonances [1]. Nanoantennas generally consist of complex two-dimensional or three-dimensional nanostructures. It is relatively expensive and difficult to describe the interac-tion between it and electromagnetic wave with a simple analytical formula. Therefore, we need to numerically simulate the interaction between nanostructures and electromagnetic waves. The re-sults provide clear guidelines for the fabrication of efficient antenna [2]. Non-diffracting beams, do not spread as they propagate. An Airy beam is a non-diffracting beam, and has the property of self-acceleration [3]. This property is particularly useful in many applications.

In this paper, we will develop an optical antenna to generate an Airy beam. The characteristics of the resulting Airy beam are analyzed, and the effects of vary parameters of the optical antenna on the Airy beam are discussed. And by adjusting the parameters, the optical antenna has potential application for generating other novel non-diffracting beams.

References [1] Bharadwaj, P., B. Deutsch, and L. Novotny, 2009: Optical antennas. Adv. Opt. Photon. 1, 438–483.[2] Kappeler, R., D. Erni, C. Xudong, et al., 2007: Field computations of optical antennas. J. Comput.

Theor. Nanosci. 4, 686–691.[3] Siviloglou, G. A., J. Broky, A. Dogariu, et al., 2007: Observation of accelerating Airy beams. Phys.

Rev. Lett. 99, 213901.

Preferred mode of presentation: Poster

Infrared limb detection of large HNO3-containing PSC particles in the Arctic winter stratosphere

Wolfgang Woiwodea,*, Michael Höpfnera, Lei Bib, Farahnaz Khosrawia,and Michelle Santeec aInstitute of Meteorology and Climate Research - Atmospheric Trace Gases and Remote Sensing

(IMK-ASF), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany bSchool of Earth Sciences, Zhejiang University, Hangzhou, China, 310027 cJet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA

*Presenting author ([emailprotected])

Growth, sedimentation and sublimation of nitric acid trihydrate (NAT) particles larger than 10 µm in polar stratospheric clouds (PSCs) are known to affect polar stratospheric ozone loss [1]. Param-eterizations of large NAT particles in atmospheric models are uncertain, since the particles are difficult to access and only few field observations are available. Satellite-borne MIPAS (Michel-son Interferometer for Passive Atmospheric Sounding) infrared limb observations were shown to be sensitive to PSC composition and, specifically, to spherical β-NAT particles with diameters below 6 µm in high volume densities [2]. Based on radiative transfer simulations involving the Mie model it was shown that the v2 mode of NO3– at 820 cm–1 allows a specific detection. How-ever, larger spherical NAT particles with sizes critical for irreversible denitrification are not ac-cessible, since the characteristic signature flattens out. The combination of Arctic airborne MIPAS and in situ field observations in December 2011 suggests that large NAT particles are highly as-pherical. Using IIM+SOV (invariant imbedding T-matrix method and separation of variables method) calculations [3], a characteristic red-shifted spectral signature below 820 cm-1 in the MI-PAS spectra was attributed to highly aspherical β-NAT particles [4].

In the presented study, we analyze capabilities of infrared limb observations of detecting large NAT particles. Our detection algorithm is based on radiative transfer simulations involving IIM+SOV calculations of highly aspherical β-NAT particles. Using MIPAS observations, large NAT particle populations during the Arctic winter 2011/12 are identified vortex-wide. The results are compared with gas phase HNO3 modulations observed by MLS (Microwave Limb Sounder).

References [1] Fahey, D. W., R. S. Gao, K. S. Carslaw, et al., 2001: The detection of large HNO3-containing particles

in the winter Arctic stratosphere. Science 291, 1026–1031.[2] Höpfner, M., B. P. Luo, P. Massoli, et al., 2006: Spectroscopic evidence for NAT, STS and ice in

MIPAS infrared limb emission measurements of polar stratospheric clouds. Atmos. Chem. Phys. 6,1201–1219.

[3] Bi, L., P. Yang, G. W. Kattawar, and M. I. Mishchenko, 2013: Efficient implementation of the invariantimbedding T-matrix method and the separation of variables method applied to large nonspherical inho-mogeneous particles. J. Quant. Spectrosc. Ra. 116, 169–183.

[4] Woiwode, W., M. Höpfner, L. Bi, et al., 2016: Spectroscopic evidence of large aspherical β-NAT par-ticles involved in denitrification in the December 2011 Arctic stratosphere. Atmos. Chem. Phys. 16,9505–9532.

Preferred mode of presentation: Oral

Light absorption enhancement of black carbon aerosols due to complex particle morphology Yu Wua,*, Tianhai Chenga, Dantong Liub, Shuaiyi Shia, Xin Zuoa, Wannan Wanga, Xiaochuan Zhanga, Can Menga, and Qi Ruoa aState Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth,

Chinese Academy of Sciences. No.20 Datun Road, Chaoyang, Beijing, 100101, China bDepartment of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou,

Zhejiang, China *Presenting author ([emailprotected]) Black carbon (BC) is formed by incomplete combustion of fossil fuels, biofuels, and biomass, and is the second most important anthropogenic contributor to global warming after CO2. Climate im-pact of BC aerosols is poorly qualified due to the systematic discrepancy between model and ob-servation estimates of BC light absorption enhancements (Eabs) after aging which transfer directly into large uncertainties in model estimates of BC radiative forcing. Until now, a proper description of Eabs varying with BC aging has not been validated, leading to a curial question of BC climate impact. In this study, BC absorption enhancements are qualified using a theoretical model consid-ering their realistic particle morphologies and mixing states dependent on aging scales. The fractal aggregated morphologies with bare, partly coated, partially encapsulated, and heavily coated states of BC-containing particles are simulated dependent on the mass ratio of non-BC and BC compo-nents in the individual BC-containing particles, and their optical properties are validated by the comprehensive laboratory and field ambient data. Our results indicate that previous conflicting results of Eabs were possibly observed in different BC aging states, which lie in the range of mod-elling descriptions. The observed Eabs can be simulated by the model considering particle mor-phology if BC aging states are exactly obtained. The small observed values of Eabs correspond to a partly aging stage with the BC particles that have inclusions and are thinly coated. The large results of Eabs are mainly produced by heavily coated BC particles in their fully aged stage. It is suggested that the predictions of Eabs varying with BC aging can be largely improved by consider-ing their realistic particle morphologies and mixing states dependent on aging scales. Preferred mode of presentation: Poster

Multiple scattering from liquid cloud measured by using a polarization lidar with two fields of view

Decheng Wua,*, Xianming Sunb, Dong Liua, Zhiqing Zhonga, Bangxin Wanga,and Yingjian Wanga,c aKey Laboratory of Atmospheric optics, Anhui Institute of Optics and Fine Mechanics, Chinese Academy

of Sciences, Hefei, Anhui 230031, China bSchool of electrical and electronic engineering, Shandong University of Technology, ZiBo, Shandong

255049, China cUniversity of Science and Technology of China, Hefei, Anhui 230031, China

*Presenting author ([emailprotected])

Liquid clouds play a key role in the earth radiation budget, the liquid droplet size and concentration are two important parameters in the research of liquid cloud radiation character. A linearly polar-ized laser pulse from lidar penetrates into liquid cloud, multiple scattering will occur in the cloud, and the lidar received multiple scattering signal will be depolarized [1]. The received multiple scattering signal will enhance the received signal intensity and depolarization ratio. The proportion of the multiple scattering signal in the received signal was mainly determined by the receiver’s field of view (FOV), liquid droplet size and concentration. The multiple scattering signal could be obtained from lidar received signals with different FOVs, and the liquid droplet size and concen-tration could be retrieved from the multiple scattering signal [2].

A polarization lidar with two FOVs was developed to retrieve liquid droplet effective size and concentration from the multiple scattering in the liquid cloud. The lidar system was introduced, and the depolarization ratio was calibrated by rotating a half-wave plate in the laser transmitter. The lidar measurements of multiple scattering from liquid cloud are shown and discussed. The results indicated that the polarization lidar with two FOVs could be employed to measure the drop-let effective size and concentration in the liquid cloud.

References [1] Bissonnette, L. R., 2005: Lidar and multiple scattering. In Lidar, edited by C. Weitkamp, Springer,

Berlin, pp. 43–103.[2] Roy G., L. Bissonnette, C. Bastille, et al., 2014: Retrieval of droplet-size density distribution from

multiple-field-of-view cross-polarized lidar signals: theory and experimental validation. Appl. Opt. 38,5202–5211.

Preferred mode of presentation: Oral/Poster

Simulation of FY-3D observations of Hurricane Maria

Hejun Xiea,*, Lei Bia, and Wei Hanb aDepartment of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou, China bNumerical Weather Prediction Center of China, National Meteorology Center of China, Beijing, China

*Presenting author ([emailprotected])

In this presentation, we report on our efforts devoted to simulating FY-3D observations of Hurri-cane with a focus on understanding the impacts of hydrometeor models on the radiative transfer. The FY-3D houses three functioning instruments in the microwave regime, namely MWRI, MWHS, MWTS, whose channels are located at atmospheric windows, absorption lines of vapor and oxygen, respectively. Cases of simulation have been conducted and we found that applying the aspherical shapes mitigates the over-scattering in mid-frequencies (e.g., 30–50 GHz) slightly by reducing the extinction of Mie shape, and enhances the scattering in high-frequencies (e.g., 89–187 GHz) prominently by reducing the asymmetry factor and single scattering albedo (SSA) of Mie shape. These findings are similar to those reported in [1], except that the simulation results of Mie shape in mid-frequencies show no “black hole” as reported in [1]. We also report our efforts on studying the impacts of vertical inhom*ogeneity of particle shapes. Specifically, we apply the optical database of 10 ice crystal habit [2], with temperature dependence of ice refractive index as its feature, to the observational operator RTTOV (Radiative Transfer for TOVS) [3]. Hydrometeor profiles of GRAPES model have been used for simulation. Hurricane Maria and several other storms in West Pacific Ocean, at various stages of development, are chosen as cases. The vertical distribution of hydrometeors of storms in [4] is used for a reference.

References [1] Geer, A. J., and F. Baordo, 2014: Improved scattering radiative transfer for frozen hydrometeors at

microwave frequencies. Atmos. Meas. Tech. 7, 1839–1860.[2] Ding, J., L. Bi, P. Yang, et al., 2016: Single-scattering properties of ice particles in the microwave

regime: temperature effect on the ice refractive index with implications in remote sensing. J. Quant.Spectrosc. Radiat. Transfer 190, 26–37.

[3] Hocking, J., P. Rayer, et al., 2018: RTTOV v12 user guide.[4] Zhou, Y., Y. Han, Y. Wu, et al., 2018: Optical properties and spatial variation of tropical cyclone cloud

systems from TRMM and MODIS in the East Asia region. J. Geophys. Res. 123, 9542–9558.

Preferred mode of presentation: Poster

Retrieving aerosol height over land via the O2 A&B bands

Xiaoguang Xua,* and Jun Wangb aJoint Center for Earth Systems Technology, University of Maryland – Baltimore County, Baltimore, MD

21228, USA bDepartment of Chemical and Biochemical Engineering, The University of Iowa, Iowa City, 52242, IA,

USA

*Presenting author ([emailprotected])

Aerosol vertical distribution is one of the most important but poorly observed variables that govern the aerosol’s radiative impacts on climate and weather. Recently, the determination of aerosol height using passive satellite measurements in the oxygen (O2) A band around 755–775 nm has been increasingly appreciated [1]. Its physical principle relies on the fact that the scattering of aerosol particles reduces the path length and the probability of light being absorbed by the under-neath O2, thus increasing the radiance in O2 A band as observed by a satellite; this brightening is strongly sensitive to the altitude of the aerosol layer. However, such a retrieval over land is chal-lenged by the high surface reflectance in the O2 A band. Measurements in the O2 B band at 685–695 nm, though engaging a relative weaker O2 absorption signal, can complement aerosol height retrieval by taking advantage of the low reflectance of a vegetation surface [2,3].

In this study, we combined radiances in both the O2 A and B bands measured by the Earth Polychromatic Imaging Camera (EPIC) to determine optical depth and layer height of biomass-burning aerosols over vegetated land surfaces. Carried by the Deep Space Climate Observatory satellite that orbits around the Earth–Sun Lagarange-1 point, EPIC observes the entire sun-lit Earth disk every 1 to 2 hours, providing Earth-reflected radiances in 10 narrow bands. In particular, our algorithm first determines the aerosol optical depth using EPIC’s atmospheric window bands (443, 551, 680, and 780 nm), then uses its O2 bands (688 and 763 nm) to derive the effective aerosol optical centroid altitude. The algorithm was applied to EPIC observations of several biomass burn-ing activities over Canada and the United States in August 2017. Validations were performed against aerosol extinction profile scanned by the space-borne lidar, CALIOP, showing an average error of less than 0.6 km in the retrieved aerosol height.

References [1] Xu, X., J. Wang, Y. Wang, and A. Kokhanovsky, 2018: Passive remote sensing of aerosol layer height.

In T. Islam, Y. Hu, A. Kokhanovsky, and J. Wang, Eds., Remote Sensing of Aerosols, Clouds, andPrecipitation, Elsevier, Amsterdam, pp.1–22.

[2] Ding, S., J. Wang, and X. Xu, 2016: Polarimetric remote sensing in O2 A and B bands: sensitivity studyand information content analysis for vertical profile of aerosols. Atmos. Meas. Tech. 9, 2077–2092.

[3] Xu X., J. Wang, Y. Wang, et al., 2018: Detecting layer height of smoke aerosols over vegetated landand water surfaces via oxygen absorption bands: hourly results from EPIC/DSCOVR satellite in deepspace. Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2018-414.

Preferred mode of presentation: Oral

Progress on inversion algorithm development for multi-angle polarimetric aerosol retrievals using AirMSPI Feng Xua,*, Gerard van Hartena, David. J. Dinera, Oleg Dubovikb, and Yoav Schechnerc

aJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA91109, USA bLaboratoire d’Optique Atmosphérique, CNRS/Université Lille-1, Villeneuve d’Ascq, France cViterbi Faculty of Electrical Engineering, Technion – Israel Institute of Technology, Haifa, Israel

*Presenting author ([emailprotected]) The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) was developed for NASA by the Jet Propulsion Laboratory to advance our understanding of the climate and air quality impacts of aerosols, clouds, and the interactions between aerosols and clouds. It performs multi-angle observations of a target area between ±67° off nadir. Imaging is made in eight spectral channels in the UV–NIR (355–935 nm), three of which (centered at 470, 660, and 865 nm) are polarimetric.

For a coupled retrieval of aerosol properties and surface reflectance, an efficient and flexible algorithm has been developed to fully capture the information content of polarimetric observations. Spatial correlation in aerosol properties is utilized to reduce the retrieval parameter space and mitigate the ill-posedness of inversion, as well as to develop a PC based fast radiative transfer model to capture variations of radiation field across an image [1]. Our retrieval imposes constraints on spatial variations of aerosol microphysical properties, spectral variations of the Bidirectional Polarization Distribution Function and angular shape of the Bidirectional Reflectance Distribution Function [2]. Retrievals were tested using remote sensing data AirMSPI acquired in recent field campaigns including the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys, the Imaging Polarimetric Assessment and Characterization of Tropospheric Particulate Matter, and the Aerosol Characterization from Polarimeter and Lidar campaigns. Validation of retrieved aerosol properties (e.g., aerosol optical depth, single scattering albedo and size distribution) were performed using coincident ground-based measurements by AERONET (NASA/GSFC) in the presence of various types of aerosols (e.g., smoke aerosols, non-spherical dust aerosols, and non-absorbing aerosols) with low to moderately high loadings. References [1] Xu, F., D. J. Diner, O. Dubovik, and Y. Schechner 2019: A correlated multi-pixel inversion approach

for aerosol remote sensing. Remote. Sens. (submitted). [2] Dubovik, O., M. Herman, A. Holdak, et al., 2011: Statistically optimized inversion algorithm for

enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations. Atmos. Meas. Tech. 4, 975–1018.

Preferred mode of presentation: Oral

Radiative transfer in plane-parallel media using spherical wavelets

Guanglang Xua,*, Antti Penttiläa , Maria Gritsevicha,b,c, Jouni Peltoniemib,and Karri Muinonena,b aDepartment of Physics, University of Helsinki, Helsinki, Finland bFinnish Geospatial Research Institute FGI, National Land Survey of Finland, Finland cInstitute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia

*Presenting author ([emailprotected])

Wavelets are among the most powerful tools in signal processing owing to their multi-resolution analysis capacity and local support in both frequency and space domain [1]. In recent years, there have been a growing interest in applying wavelet-based methods to solve partial differential equations [2]. The advantages of these methods in solving partial differential equations, in particular the radiative transfer equation, include their adaptivity, sparsity [3], and, more importantly, the feasibility of obtaining data-driven solutions [4]. In this work, we will present a spherical-wavelet-based method for solving the scalar radiative transfer equation in plane-parallel media. In contrast to the conventional methods, such as the discrete-ordinates and adding/doubling methods [5], the monochromatic scalar radiance and single-scattering phase functions will be represented using spherical wavelets in a sparse and adaptive way [6]. The solution to the equation will then be obtained by combining a finite-difference solver. Owing to the capability of data processing using wavelets, this method could open more of the opportunities for cooperation between experiments and numerical simulations.

References [1] Mallat, S., 1999: A Wavelet Tour of Signal Processing. Elsevier, Amsterdam.[2] Mehra, M., and N. K. R. Kevlahan, 2008: An adaptive wavelet collocation method for the solution of

partial differential equations on the sphere. J. Comput. Phys. 227, 5610–5632.[3] Widmer, G., R. Hiptmair, and C. Schwab, 2008. Sparse adaptive finite elements for radiative transfer. J.

Comput. Phys. 227, 6071–6105.[4] Matusik, W., 2003: A data-driven reflectance model (doctoral dissertation, Massachusetts Institute of

Technology).[5] Liou, K. N., 2002: An Introduction to Atmospheric Radiation. Elsevier, Amsterdam.[6] Schröder, P., and W. Sweldens, 1995: Spherical wavelets: efficiently representing functions on the

sphere. In Proceedings of the 22nd Annual Conference on Computer Graphics and InteractiveTechniques. American Chemical Society, Washington, DC, pp. 161–172.

Preferred mode of presentation: Oral

Debye series analysis of plane wave scatteringby a charged sphere

Yiming Yanga,†, Yinan Fenga, and Renxian Lia,b,* aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an

710071,China

†Presenting author ([emailprotected]) *Corresponding author ([emailprotected])

Electromagnetic scattering has applications in optical tweezers [1], optical communications [2], etc. Most of these applications involve the interaction of a plane wave with a particle. Most studies about the interaction of waves with particles are based on the assumption that the particles are not charged. However, most encountered particles are charged owing to many reasons, for instance, frequent collisions between particles or contacts with reactor walls. Many researches have been devoted to the scattering of a plane wave by a charged sphere [3–5] based on the Lorenz–Mie theory (LMT), which is a rigorous solution of the Maxwell equations and contains all the effects that contribute to scattering. However, the LMT gives few clues to the scattering processes. By writing each term of the Mie series as another infinite series, the Debye series can give a physical interpretation of various scattering processes [6–9].

In this paper, the Debye series is employed to solve the plane wave scattering by a charged sphere, and various scattering phenomena, such as rainbows, are analyzed. The far-field scattered intensity of a charged sphere illuminated by a plane wave is studied, and the effects of various parameters (including the charge, scattering process (namely Debye mode p), etc.) on the far-field scattered intensities are mainly discussed. Such results have important applications in various fields, including particle sizing, optical tweezers, etc.

References

[1] Curtis, J. E., B. A. Koss, and D. G. Grier, 2002: Dynamic holographic optical tweezers. Opt. Commun.207, 169–175.

[2] Anguita, J. A., J. Herreros, and J. E. Cisternas, 2012: Generation and detection of multiple coaxialvortex beams for free-space optical communications. In 2012 CLEO.

[3] Gong, S., R. Li, Y. Liu, et al., 2018: Scattering of a vector Bessel vortex beam by a charged sphere. J.Quant. Spectrosc. Radiat. Transfer 215, 13–24.

[4] Klačka, J., and M. Kocifaj, 2007: Scattering of electromagnetic waves by charged spheres and somephysical consequences. J. Quant. Spectrosc. Radiat. Transfer 106, 170–183.

[5] Bohren, C. F., and A. J. Hunt, 1977: Scattering of electromagnetic waves by a charged sphere. Can. J.Phys. 55, 1930–1935.

[6] Li, R., X. Han, H. Jiang, et al., 2006: Debye series for light scattering by a multilayered sphere. Appl.Opt. 45, 1260–1270.

[7] Hovenac, E. A., and J. A. Lock, 1992: Assessing the contributions of surface waves and complex raysto far-field Mie scattering by use of the Debye series. J. Opt. Soc. Am. A 9, 781–795.

[8] Shen, J., H. Wang, B. Wang, et al., 2010: Stability in Debye series calculation for light scattering byabsorbing particles and bubbles. J. Quant. Spectrosc. Radiat. Transfer 111, 772–781.

[9] Li, R., X. Han, L. Shi, et al., 2007: Debye series for Gaussian beam scattering by a multilayered sphere.Appl. Opt. 46, 4804–4812.

Preferred mode of presentation: Oral/Poster

Computing one-way edge modes in gyromagnetic photonic crystals by Dirichlet-to-Neumann maps Huajiao Yang and Zhen Hu*

Department of Mathematics, Hohai University, Nanjing, 210098, China *Presenting author ([emailprotected]) Anisotropic photonic crystals (PhCs) give rise to devices with tunable physical properties and lead to interesting phenomena, such as one-way edge modes in gyromagnetic PhCs. These modes are confined at the edge of certain two-dimensional magneto-optical (MO) PhCs and pos-sess group velocities pointing in only one direction, determined by the direction of an applied dc magnetic field. Recently, one-way edge modes have been found at the edge between an MO square lattice PhC and a regular PhC [1], at the zigzag edge of a MO honeycomb lattice PhC [2], in an yttrium-iron-garnet (YIG) PhC slab with triangular lattice [3], and at the edge between MO honeycomb lattice PhCs within different topological phases [4]. To analyze one-way edge modes, efficient numerical methods are essential.

In this talk we present an efficient numerical method to compute one-way edge modes in gy-romagnetic PhCs. Our method is based on the Dirichlet-to-Neumann (DtN) maps. By using the DtN map of a supercell, a linear eigenvalue problem with relatively small matrices is formulated on two boundaries of the supercell to solve the edge modes with high accuracy. The eigenvalue is related to the wavenumber of edge modes and the angular frequency is a given parameter. References [1] Wang, Z., Y. D. Chong, J. D. Joannopoulos, and M. Soljacic, 2008: Reflection-free one-way edge

modes in a gyromagnetic photonic crystal. Phys. Rev. Lett. 100, 013905. [2] Ao, X., Z. Lin, and C. T. Chan, 2009: One-way edge mode in a magneto-optical honeycomb photonic

crystal. Phys. Rev. B 80, 033105. [3] Liu, K., L. Shen, and S. He, 2012: One-way edge mode in a gyromagnetic photonic crystal slab. Opt.

Lett. 37, 4110–4112. [4] Lu, J., X. Chen, W. Deng, M. Chen, and J. Dong, 2018: One-way propagation of bulk states and ro-

bust edge states in photonic crystals with broken inversion and time-reversal symmetries. J. Opt. 20, 075103.

Preferred mode of presentation: Oral

Preliminary exploration of radiative propertiesof mixed-phase clouds

Bingqi Yi* and Qing Luo

School of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Zhuhai, China

Southern Laboratory of Ocean Science and Engineering (Guangdong, Zhuhai), Zhuhai, China

*Presenting author ([emailprotected])

Mixed-phase clouds are ubiquitous in the troposphere. They play important roles in various processes related to radiative energy balance of the Earth system. However, due to their complex nature, mixed-phase cloud optical properties are difficult to calculate and the corresponding cloud radiative effects remain highly uncertain [1].

In this study, we present preliminary results of mixed-phase cloud optical properties calculated based on different internal and external mixing assumptions of ice and liquid water droplets with various sizes and mixing ratios. A comprehensive ice scattering property database [2] is used, and the Lorenz–Mie theory is applied to liquid water cloud droplets. Similar to Yang et al. [3], our results show that the mixing process is critical in modulating the optical properties of mixed-phase clouds compared with hom*ogeneous ice or liquid water clouds.

References [1] Korolev, A., G. M. McFarquhar, P. R. Field, C. Franklin, P. Lawson, Z. Wang, and M. Wendisch,

2017: Mixed‐phase clouds: progress and challenges. Meteorol. Monogr. 58, Chapter 5.[2] Yang, P., L. Bi, B. A. Baum, K.-N. Liou, G. W. Kattawar, M. I. Mishchenko, and B. Cole, 2013:

Spectrally consistent scattering, absorption, and polarization properties of atmospheric ice crystals atwavelengths from 0.2 to 100 µm. J. Atmos. Sci. 70, 330–347.

[3] Yang P., H. Wei, B. A. Baum, H. Huang, A. J. Heymsfield, Y. X. Hu, B. C. Gao, and D. D. Turner,2003: The spectral signature of mixed-phase clouds composed of non-spherical ice crystals andspherical liquid droplets in the terrestrial window region. J. Quant. Spectrosc. Radiat. Transfer 79–80,1171–1188.

Preferred mode of presentation: Oral

Unidirectional reflectionless property of periodic structures with PT-symmetry Lijun Yuan

College of Mathematics and Statistics, Chongqing Technology and Business University, 400067 Chongqing, China ([emailprotected])

Unidirectional reflectionless property is the phenomenon wherein the reflection is zero for an in-cident wave coming from one side and nonzero for an incident wave coming from the other side [1]. It has been found for many structures such as PT-symmetric optical fibers, waveguides, cou-pled resonator systems, etc. In this talk, I will study the unidirectional reflectionless property of 2D structures with 1D periodicity and PT-symmetry (i.e., with balanced gain and loss). The exist-ence of the unidirectional reflectionless property is proved theoretically by using the S-matrix and the symmetry. Numerical examples will be presented to show that invisibility can happen by tun-ing structure parameters such that the phase of the transmitted wave is zero. Reference [1] Huang, Y., Y. Shen, C. Min, S. Fan, and G. Veronis, 2017: Unidirectional reflectionless light propaga-

tion at exceptional points. Nanophotonics 6, 977–996. Preferred mode of presentation: Oral

Analysis of energy budget for scattering of fields induced by nearby sources Maxim A. Yurkina,b,* and Alexander E. Moskalenskya,b aVoevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Institutskaya str. 3, 630090,

Novosibirsk, Russia bNovosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia *Presenting author ([emailprotected]) The frequency-domain volume integral equation (VIE) is a general framework for theoretical anal-yses and numerical simulations of scattering by particles of arbitrary shape and internal structure. The VIE has been known for more than 60 years, but a number of issues remained, which recently revived the interest in this subject. This led to a rigorous derivation of the VIE for a set of multi-layered particles with sharp edges and corners [1], further extended to general incident fields, in-cluding those caused by sources located near the scatterer [2]. The only missing element is the energy budget for such general scattering problem. Optical cross sections (extinction, absorption, and scattering) are defined through the power rates (integrals of the Poynting vectors over the closed surfaces) in many textbooks on light-scattering theory. However, those definitions are in-complete and/or ambiguous in the case of source-induced fields.

We provide rigorous definitions of various components of the energy budget for scattering of source-induced electromagnetic fields by a finite non-magnetic object. We use the VIE framework and define power rates in terms of integrals of the Poynting vector over various surfaces, enclosing some or all of the impressed sources, the scatterer, and the environment (such as a planar multi-layered substrate). Thus, we generalize the conventional cross sections and obtain new interrela-tions analogous to the well-known optical theorem. We rigorously treat the strong singularity of the VIE kernel, but keep derivations accessible to a wide audience. The defined power rates are further related to the decay-rate enhancement and apparent quantum yield of an arbitrary emitter, which are the core concepts in nanophotonics, surface-enhanced Raman scattering, and electron-energy-loss spectroscopy. We also discuss the practical calculation of the power rates and decay-rate enhancements in the framework of the discrete dipole approximation (DDA). In particular, we derive the volume-integral expression for the scattered power and use it to prove the automatic satisfaction of the optical theorem irrespective of the discretization level. Thus, the optical theorem cannot be used as an internal measure of the DDA accuracy. The details are given in Ref. [3].

References [1] Yurkin, M. A., and M. I. Mishchenko, 2018: Volume integral equation for electromagnetic scattering:

rigorous derivation and analysis for a set of multilayered particles with piecewise-smooth boundaries in a passive host medium. Phys. Rev. A 97, 043824.

[2] Mishchenko, M. I., and M. A. Yurkin, 2018: Impressed sources and fields in the volume-integral-equation formulation of electromagnetic scattering by a finite object: a tutorial. J. Quant. Spectrosc. Radiat. Transfer 214, 158–167.

[3] Moskalensky, A. E., and M. A. Yurkin, 2019: Energy budget and optical theorem for scattering of source-induced fields. Phys. Rev. A, submitted.

Preferred mode of presentation: Oral

Determination of thermal accommodation coefficient and primary particle size of soot through light scattering method

Junyou Zhang, Hong Qi*, and Liming Ruan

Harbin Institute of Technology, Harbin,150001, China

*Presenting author ([emailprotected])

Soot particles are considered to be the second most important factor in the anthropogenic radiative forcing underlying climate change and can influence cloud formation [1]. Airborne soot also has negative impacts on human health, both directly and as a carrier of other toxic materials [2]. Light scattering-based methods, such as elastic light scattering (ELS) and laser-induced incandescence (LII), provide non-invasive diagnostic techniques for characterizing the morphological properties of these particles. Unfortunately, the morphology measurement involves solving an inverse prob-lem, so an uncertainty of some key LII model parameters like the thermal accommodation coeffi-cient (T) will lead to obviously inaccurate results. Considering the debate on the actual value of T employed in the LII model [3], it is worth simultaneously retrieving T and target morphology parameters from the temporal LII signal. In this work, the fractal dimension and aggregate size distribution of polydisperse soot particles are retrieved from the relative intensity of angular ELS, which is based on our previous work [4]. These parameters determined by ELS are then used as input parameters of the temporal LII model to simultaneously retrieve the thermal accommodation coefficient and primary particle size.

References [1] Bond, T. C, and R. W. Bergstrom, 2006: Light absorption by carbonaceous particles: an investigative

review. Aerosol Sci. Technol. 40, 27–67.[2] Bond, T. C, S. J. Doherty, et al., 2013: Bounding the role of black carbon in the climate system: a

scientific assessment. J. Geophys. Res. Atmos. 118, 5380–5552.[3] Michelsen, H. A., C. Schulz, et al., 2015: Laser-induced incandescence: particulate diagnostics for

combustion, atmospheric, and industrial applications. Prog. Energ. Combust. 51, 2–48.[4] Zhang, J. Y., H. Qi, et al., 2019: Retrieval of fractal dimension and size distribution of non-compact

soot aggregates from relative intensities of multi-wavelength angular-resolved light scattering. Opt.Express 27, 1613–1631.

Preferred mode of presentation: Poster

Optical force on irregular and inhom*ogeneous particles by an Airy light-sheet using discrete dipole approximation

Jiaming Zhanga,*, Renxian Lia,b,**, Han Suna, Ningning Songa, Shu Zhanga,and Bojian Weia aSchool of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University,

Xi’an 710071, China

*Presenting author ([emailprotected])**Corresponding author ([emailprotected])

Optical tweezers [1] have been become a powerful tool for non-contact manipulation of micro-scopic objects and have found a huge range of applications in various fields [2]. The discrete dipole approximation (DDA) is an efficient tool to calculate optical forces on particles with various shapes illuminated by any beam [3]. Airy light-sheet is a two-dimensional Airy beam and has been widely utilized in optical particle clearing, particle transport, micromanipulation because of their advantages of non-diffraction, self-acceleration, and self-healing [4].

In this research, the angular spectrum decomposition method is used to derive the electromag-netic field components of an Airy light-sheet. Numerical computations for axial and transverse radiation force are computed for x-polarized Airy light-sheet with different transverse scale ω0, modulation parameter a, and beam center. ω0 involves the size of lobes and the number of side lobes. With the increasing of ω0, all the lobes will expand and the number of side lobes will reduce. a involves the intensity of lobes, and the amplitudes of each lobe will decrease with being greater, while the contrast between the main and side lobes is even more obvious. As the particles shift off the axis in the plane perpendicular to the propagating direction, both stable and unstable equilib-rium points are obtained, depending on the size parameters, transverse scale, and modulation pa-rameter.

References [1] Shaw, L. A., C. M. Spadaccini, and J. B. Hopkins, 2017: Scanning holographic optical tweezers. Opt.

Lett. 42, 2862–2865.[2] Liyang, Y., O. V. Minin, W. Zengbo, et al., 2018: Photonic hook: a new curved light beam. Opt. Lett.

43, 771–774.[3] Donald, J. M., A. Golden, and S. G. Jennings, 2009: A novel high-performance computational frame-

work for the discrete dipole approximation. Int. J. High Perf. Comput. Appl. 23, 42–61.[4] Vettenburg, T., H. I. C. Dalgarno, J. Nylk, et al., 2014: Light-sheet microscopy using an Airy beam.

Nat. Meth. 11, 541.

Preferred mode of presentation: Poster

Sensitivity analysis of polarimetric remote sensing of atmospherically-processed brown carbon aerosol

Chenchong Zhanga,*, William R. Heinsona, Benjamin Sumlina, Michael J. Garayb, Olga Kalashnikovab, and Rajan K. Chakrabartya aWashington University in St. Louis, St. Louis, MO 63130, USA bJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

*Presenting author ([emailprotected])

Biomass burning is an important emission source for brown carbon (BrC) aerosol, which has been shown to significantly modulate regional atmospheric radiative forcing by strongly absorbing in the near-UV solar spectra. These particles could also affect cloud microphysical characteristics due to their solubility in a liquid medium. Multiangle spectropolarimetric remote sensing tech-niques have been found great use in improving the characterization of columnar properties of the atmospheric BrC including its composition and particle vertical distribution [1].

Freshly emitted BrC aerosol has been shown to quickly undergo atmospheric processing re-sulting in changes of its optical and physicochemical properties on time-scales ranging between minutes to hours [2]. Current remote sensing retrieval algorithms fail to take into consideration parameterizations of BrC aerosol microphysical properties during atmospheric processing. In this study, we propose forward modeling to quantitatively analyze the sensitivity of remote sensing parameters to changing BrC aerosol properties as a function of atmospheric processing. We track the evolution of BrC aerosol after emission by configuring the atmospheric layers in numerical model with aerosols of different aging stages. By doing this, the spectropolarimetric pattern of BrC aerosol will be tracked over a long time-scale. The validation of our forward modeling results will be made with observational data collected by the Jet Propulsion Laboratory’s Airborne Multiangle SpectroPolarimetric Imager (AirMSPI).

References [1] Diner, D. J., M. J. Garay, O. V. Kalashnikova, et al., 2013: Airborne multiangle spectropolarimetric

imager (AirMSPI) observations over California during NASA’s polarimeter definition experiment (PO-DEX). Proc. SPIE 8873, 88730B.

[2] Sumlin, B. J., A. Pandey, M. J. Walker, R. S. Pattison, B. J. Williams, and R. K. Chakrabarty, 2017:Atmospheric photooxidation diminishes light absorption by primary brown carbon aerosol from bio-mass burning. Environ. Sci. Technol. Lett. 4, 540–545.

Preferred mode of presentation: Poster

3-D tomographic morphology of soot aggregates from coal combustion and associated optical properties Chenchong Zhanga,*, William R. Heinsona, Jingkun Jiangb, and Rajan K. Chakrabartya aWashington University in St. Louis, St. Louis, MO 63130, USA bTsinghua University, Beijing, 100084, China *Presenting author ([emailprotected]) Soot aggregates constitute the major fraction of particulate matter emitted from anthropogenic sources. Freshly emitted soot particles have complex fractal-like structures. These complex mor-phologies can significantly influence particle microphysical and optical properties, thereby im-pacting the earth’s radiative forcing. Accurate parameterization of aggregate morphology is a pre-requisite for quantitatively evaluating soot spectral radiative properties.

Electron tomography is a powerful technique which can detect the detailed three-dimensional (3-D) structure of aggregates. However, a defect, namely the missing wedge, inherent to limited-angle projection images limits the accuracy of the final 3-D reconstruction. Here, we demonstrate a novel tomography technique for 3-D reconstruction of soot aggregates sampled from a coal-fired reactor in China. Compared to traditional weighted back projection and iterative reconstruction techniques, we incorporate total variation minimization to compensate for the missing wedge ar-tefacts [1]. The reconstructed soot particle models precisely capture the detailed morphological information of the aggregates, for example, the exact shapes of primary particles and the necking between monomers. Next, we calculate the Fourier Transform of the density auto-correlation func-tion of the voxels (also known as the particle structure factor) to accurately characterize the fractal morphology of the reconstructed particles. Our goal here is to validate the conventional viewpoint regarding combustion-generated fractal aggregates, formed via diffusion limited cluster-cluster aggregation, yielding a universal mass fractal dimension of 1.8 [2]. Finally, we conclude this work by applying the discrete-dipole approximation on reconstructed aggregate models to derive spec-tral optical properties including scattering and absorption cross-sections, and asymmetry and Stokes parameters. References [1] Goris, B., W. Van den Broek, K. J. Batenburg, H. H. Mezerji, and S. Bals, 2012: Electron tomography

based on a total variation minimization reconstruction technique. Ultramicroscopy 113, 20–130. [2] Sorensen, C.M., 2001: Light scattering by fractal aggregates: a review. Aerosol Sci. Technol. 35, 648–

687. Preferred mode of presentation: Oral

Metasurface based generation of an Airy beam

Shu Zhanga,*, Renxian Lia,b,**, Jiaming Zhanga, Bojian Weia, Ningning Songa,and Han Suna

a School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China. bCollaborative Innovation Center of Information Sensing and Understanding, Xidian University,

Xi’an 710071, China.

*Presenting author ([emailprotected])**Corresponding author ([emailprotected], [emailprotected])

Airy beams have many characteristics such as self-bending [1], no diffracting [2], and lateral ac-celeration [3], and put a great impact on the applications of the trapping in the optical potential, converging transmitted energy during the bending process, and long-distance transmission. There-fore, there are many optical devices to generate Airy beam. To overcome the defect of low loss and heavy attenuation in conventional optical devices, novel devices based on a metasurface are developed [4,5], and they reduce the system complexity and improve system reliability. The metasurface is a material with a thickness less than the wavelength of the incident beam. It has characteristics of flattening and low loss.

In this paper, we design a metasurface to generate an Airy beam with low loss and high effi-ciency using commercial software COMSOL. The characteristics of the resulting Airy beam are tested and verified. The metasurface can be modified to generate arbitrary beams.

References [1] Broky, J., G. A. Siviloglou, A. Dogariu, and D. N. Christodoulides, 2008: Self-healing properties of

optical Airy beams. Opt. Express 16, 12880–12891.[2] Besieris, I. M., and A. M. Shaarawi, 2007: A note on an accelerating finite energy Airy beam. Opt. Lett.

32, 2447–2449.[3] Siviloglou, G., J. Broky, A. Dogariu, and D. Christodoulides, 2007: Observation of accelerating Airy

beams. Phys. Rev. Lett. 99, 213901.[4] Wang, S., X. Wang, and Y. Zhang, 2017: Simultaneous Airy beam generation for both surface plas-

mon polaritons and transmitted wave based on metasurface. Opt. Express 25, 23589–23596.[5] Chen, H.-T., et al., 2016: A review of metasurfaces: physics and applications. Rep. Prog. Phys. 79,

076401.

Preferred mode of presentation: Oral

Aerosol optical properties and their impactson cloud remote sensing

Chuanfeng Zhao* and Xin Yang aCollege of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, China

*Presenting author ([emailprotected])

Aerosols, by scattering and absorbing solar radiation, reduce the energy reaching the ground sur-face. The absorptive properties of aerosols could result in different impacts on the surface radiation. In general, for the same amount of aerosols, the larger the absorption of aerosols, the more the reduction of solar radiation at the surface. Based on the slope ratio of surface radiation to the atmospheric visibility, we first determine the relative strength of aerosol absorption in different regions in China. It is found that the aerosols in Central China have strong absorption [1].

The strong absorption of aerosols in China could further impact the cloud remote sensing based on spectral radiation in visible wavelengths. In principle, it could make the cloud optical depth overestimated and cloud droplet effective radius underestimated for ground-based retrievals since the aerosols reduce the downwelling solar radiation reaching the surface. In contrast, the aerosols could make the cloud optical depth underestimated and cloud droplet effective radius overesti-mated for satellite-based retrievals since they reduce the cloud albedo by absorbing the solar radi-ation. These two different effects of aerosols on ground- and satellite-based cloud remote sensing could make the retrievals from these two different methods different from each other [2].

References [1] Yang, X., C. Zhao, L. Zhou, Y. Wang, and X. Liu, 2016: Distinct impact of different types of aerosols

on surface solar radiation in China. J. Geophys. Res. Atmos. 121, 6459–6471.[2] Li, Z., F. Zhao, J. Liu, M. Jiang, C. Zhao, and M. Cribb, 2014: Opposite effects of absorbing aerosols

on the retrievals of cloud optical depth from spaceborne and ground-based measurements. J. Geophys.Res. Atmos. 119, 5104–5114.

Preferred mode of presentation: Oral

Contribution of weak localization to lidar returns from atmospheric particles

Chen Zhou

Nanjing University, Nanjing, China ([emailprotected])

Lidars have been widely used to detect clouds and aerosols in the atmosphere, and the particle properties can be retrieved from their lidar backscattering signals upon a series of assumptions and approximations. The lidar returns from atmospheric particles might be enhanced by weak locali-zation in both single scattering and multiple scattering processes, depending on particle properties and the off-backscatter observation angle of lidar.

The lidar returns from large aerosol particles and cloud particles may be enhanced by weak localization in single scattering. Solution of Maxwell’s equations to the problem of single scatter-ing can be expanded into iterative series in an order-of-scattering form, where the interference between conjugate terms representing reversible sequences of elementary scatterers is constructive at the backscattering direction, resulting in a coherent backscatter enhancement (CBE) [1]. The backscattering phase function of randomly oriented particles is amplified by CBE with an ampli-fication factor between 1 and 2 depending on particle habit and refractive index. The angular width of the CBE-induced backscattering peak line for a specific particle habit is inversely proportional to the particle size parameter, and CBE peak of cloud and weakly absorbing aerosol particles is wide enough to enhance the returns of most actual lidars.

Lidar backscatter might also be enhanced by interference between conjugate reversible wave paths in multiple scattering (coherent backscattering [2]). However, the angular width of the co-herent backscattering peak line in multiple scattering is narrow due to the relatively large distances between neighboring cloud and aerosol particles, so the spaceborne lidar returns would not be enhanced by coherent backscattering due to relatively large off-backscattering observation angle.

References [1] Zhou, C., 2018: Coherent backscatter enhancement in single scattering. Opt. Express, 26, A508–A519.[2] Mishchenko, M. I., L. D. Travis, and A. A. Lacis, 2006: Multiple Scattering of Light by Particles:

Radiative Transfer and Coherent Backscattering. Cambridge University Press, Cambridge, UK.

Preferred mode of presentation: Oral

Model development for nighttime light radiative transfer and application to VIIRS Day Night Band remote sensing of aerosols

Meng Zhoua,*, Xiaoguang Xub, Jun Wanga, Sepehr Roudinia, Thomas Pongettic, and Stanley Sander3

aUniversity of Iowa, Iowa Advanced Technology Laboratories, Iowa City, IA 52242-1503, USA bUniversity of Maryland – Baltimore County, 1000 Hilltop Cir., Baltimore, MD 21250, USA cNASA Jet Propulsion Laboratory (JPL), 4800 Oak Grove Dr., Pasadena, CA 91109, USA

*Presenting author ([emailprotected])

The observation of nighttime aerosol condition is important because of aerosol effects on visibility, air quality, and public health. By measuring visible light at night from space, the Visible Infrared Imaging Radiometer Suite Day/Night Band (VIIRS DNB) [1] sensor onboard the NPP and JPSS-1 satellites provides the research and operational communities the capability to explore nighttime atmospheric optical and aerosol properties. To quantitatively use the DNB data for nighttime remote sensing, we developed a nighttime radiative transfer model based on the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) [2]. With the new development, the UNL-VRTM can simulate light transfer at night with careful consideration of surface light spectra from various types of artificial light sources, gas flares, and wildfires, as well as moonlight and DNB relative sensor response function (RSR).

We used this model to investigate questions key to the remote sensing of aerosol using VIIRS DNB observations: (1) How significantly can the VIIRS RSR impact the AOD retrieval? (2) How much AOD retrieval bias is there for different surface light spectra when a wavelength independent spectrum (or continuum) is used? (3) For cost efficiency, if only one channel is used to retrieve the AOD, what is the equivalent wavelength of our daily life lamps? Our results show the following. First, without considering the DNB RSR, there can be greater than a 100% bias when the AOD is relatively low (less than 0.5). This retrieval bias decreases as the AOD increases. Second, the AOD retrieval bias is spectrum dependent. When a wavelength independent spectrum is used to retrieve the AOD, the bias is around –10% for light-emitting diodes and fluorescent lamps. While for high pressure sodium lamp, this bias is around –30%. This retrieval bias also decreases with increasing AOD. Third, the equivalent wavelength with respect to the AOD retrieval for the chosen three lamp spectra is around 585 nm.

References [1] Miller, S., et al., 2013: Illuminating the capabilities of the Suomi National Polar-Orbiting Partnership

(NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band. Remote Sens. 5, 6717–6766.

[2] Wang, J., et al., 2014: A numerical testbed for remote sensing of aerosols, and its demonstration forevaluating retrieval synergy from a geostationary satellite constellation of GEO-CAPE and GOES-R.J. Quant. Spectrosc. Radiat. Transfer 146, 510–528.

Preferred mode of presentation: Oral/Poster

How can the discrete dipole approximation reproduce morphology-dependent resonances of spheres? Yingying Zhua, Chao Liua,*, and Maxim A. Yurkinb,c

aSchool of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044, Jiangsu Province, China

bVoevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia

cNovosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia *Presenting author ([emailprotected]) During the development and application of a scattering algorithm, its accuracy is normally validated by comparing with the results for spherical particles given by the exact Lorenz–Mie theory. The morphology-dependent resonances (MDRs) show significant influences on the scattering properties of particles within sufficiently narrow size ranges [1–3], and may affect the validation of the numerical models. It is unclear whether numerical models that solve Maxwell’s equations by discretizing the space could reproduce the MDRs of spheres. This presentation investigates the performance of the Discrete Dipole Approximation (DDA) on modeling the scattering properties with the MDRs. Our results indicate that the DDA can capture both the peak position and peak value in the extinction efficiency over the size parameter caused by an MDR only if an extremely fine discretization is used. To be more specific, the dipole size has to have size similar to the width of the MDRs to produce the accurate MDR results. However, the extinction curves simulated by the DDA (even at relatively coarse discretization) can be fitted with a Lorentzian as well as Lorenz–Mie results [4]. Moreover, the convergence of the corresponding peak parameters with refining discretization is relatively smooth, which allows using Richardson extrapolation (to zero dipole size) to accurately restore the reference Mie values. References [1] Chýlek, P., J. T. Kiehl, and M. K. W. Ko, 1978: Optical levitation and partial-wave resonances. Phys.

Rev. A 18, 2229–2233. [2] Johnson, B. R., 1993: Theory of morphology-dependent resonances: shape resonances and width

formulas. J. Opt. Soc. Am. A 10, 343–352. [3] Conwell, P. R., P. W. Barber, and C. K. Rushforth, 1984: Resonant spectra of dielectric spheres. J. Opt.

Soc. Am. A 1, 62–67. [4] Fuchs, R and K. L. Kliewer, 1968: Optical modes of vibration in an ionic crystal sphere. J. Opt. Soc.

Am. 58, 319–330. Preferred mode of presentation: Oral

mailto:[emailprotected]

Near-backscattering optical properties of aerosols Ruirui Zong*, Wushao Lin, and Lei Bi

Department of Atmospheric Sciences, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, China *Presenting author ([emailprotected]) Knowledge of backscattering optical properties of aerosol particles plays an important role in ac-tive lidar remote sensing and particle characterization studies. However, it is challenging to accu-rately measure the backscattering optical properties of aerosols in a laboratory environment. On the other hand, accurate computation of backscattering optical properties of large-sized model par-ticles has also been a challenging research subject. Therefore, a combination of near-backscatter-ing measurements and modeling analysis [1] would be valuable to obtain a better knowledge of backscattering optical properties at 180°. In this study, we employed an invariant imbedding T-matrix method (IITM) [2,3] to compute the single scattering properties of randomly oriented par-ticles with different size parameters, shape parameters (i.e., aspect ratio and roundness parameter), and refractive indices. For case studies, we applied the IITM to randomly oriented super-spheroids with a size parameter up to 150. The differences of lidar ratios and depolarization ratios at near-backscattering angles (173°, 175°, 178°) and exact-backscattering angle (180°) are quantified with respect to the size parameter and aerosol refractive indices. The findings in this study will be help-ful to understand how backscattering ratios change at near backscattering angles, and the uncer-tainties if optical properties are measured at near-backscattering directions instead of 180°. References [1] Järvinen, E., O. Kemppinen, T., Nousiainen, et al., 2016: Laboratory investigations of mineral dust

near-backscattering depolarization ratios. J. Quant. Spectrosc. Radiat. Transfer 178, 192–208. [2] Bi, L., and P. Yang, 2014: Accurate simulation of the optical properties of atmospheric ice crystals with

invariant imbedding T-matrix method. J. Quant. Spectrosc. Radiat. Transfer 138, 17–35. [3] Bi, L., W. Lin, D. Liu, and K. Zhang, 2018: Assessing the depolarization capabilities of nonspherical

particles in a super-ellipsoidal shape space. Opt. Express 26, 1726–1742.

Preferred mode of presentation: Poster