The polarimetric characteristics of dust with irregular shapes: evaluation of the spheroid model for single particles
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Published:2022-05-06
Issue:9
Volume:15
Page:2767-2789
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Luo JieORCID, Li Zhengqiang, Fan Cheng, Xu Hua, Zhang Ying, Hou Weizhen, Qie Lili, Gu Haoran, Zhu Mengyao, Li Yinna, Li KaitaoORCID
Abstract
Abstract. In the atmosphere, the dust shapes are various, and a single model is difficult to represent the complex shapes of dust. We proposed a tunable model to represent dust with various shapes. Two tunable parameters were used to represent the effects of the erosion degree and binding forces from the mass center, respectively. Thus, the model can represent various dust shapes by adjusting the tunable parameters. To evaluate the applicability of the single spheroid model in calculating the optical properties of single dust with irregular shapes, the aspect ratios of spheroids were retrieved by best fitting the phase function of dust with irregular shapes. In this work, the optical properties and polarimetric characteristics of irregular dust with a diameter range of 0.2–2.0 µm were investigated. Our findings show that the dust shapes have a substantial impact on the scattering matrix, and sometimes the sign of elements of the scattering matrix could be modified by changing the tunable parameters. The applicability of the spheroid model is significantly affected by the erosion degree and binding forces, and substantial deviations could be observed when the dust diameter is in the range of 0.8–2.0 µm. The F11 relative differences of approximately 100 % between dust with irregular shapes and best-fitted spheroids could be observed in certain scattering angles. The maximum differences in other elements between irregular dust particles and best-fitted spheroids can reach approximately 0.3–0.8. Besides, the signs of F12/F11, F33/F11, F34/F11 and F44/F11 can be modified from negative to positive at some scattering angles if substituting the irregular dust with best-fitted spheroids. As the binding force is small, the deviation of extinction or scattering cross-section generally increases with the erosion degree, and the relative differences between dust with irregular shapes and spheroids can reach approximately 30 % when the erosion degree is large, while the differences are mitigated with the binding force increasing. Besides, with the binding force increasing, the aspect ratio is closer to 1:1. The deviations of the spheroid model in estimating the polarized light were also investigated using the successive-order-of-scattering (SOS) vector radiative transfer (VRT) model. With a diameter (dp) of 0.2 µm, the relative difference of normalized radiance does not exceed 3 %, and the absolute values of the deviation of the polarized bidirectional reflectance factor (PBRF) and the ratio of radiance to polarized intensity (DoLP) are below 0.005 and 0.02, respectively. However, with the particle size increasing, the difference becomes much more substantial. The relative difference of the normalized radiance can exceed 10 %, and the deviations of the PBRF and DoLP can vary in the ranges of −0.015 to 0.025 and −0.05 to 0.15, respectively. Thus, the single spheroid model may lead to non-negligible deviations for estimating the polarimetric characteristics of single dust particles with more complex shapes. In this work, only the optical properties of single particles were considered. In the future, the applicability of an ensemble of spheroidal particles for reproducing the scattering properties and polarimetric characteristics of an ensemble of irregularly shaped dust particles should be further investigated.
Funder
National Natural Science Foundation of China
Publisher
Copernicus GmbH
Subject
Atmospheric Science
Reference68 articles.
1. Bi, L., Yang, P., Kattawar, G. W., and Kahn, R.: Modeling optical properties of mineral aerosol particles by using nonsymmetric hexahedra, Appl. Optics, 49, 334–342, https://doi.org/10.1364/AO.49.000334, 2010. a 2. Cai, W., Ni, X., Gayen, S. K., and Alfano, R. R.: Analytical cumulant solution of the vector radiative transfer equation investigates backscattering of circularly polarized light from turbid media, Phys. Rev. E, 74, 056605, https://doi.org/10.1103/PhysRevE.74.056605, 2006. a 3. Chou, C., Formenti, P., Maille, M., Ausset, P., Helas, G., Harrison, M., and Osborne, S.: Size distribution, shape, and composition of mineral dust aerosols collected during the African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass-Burning Experiment field campaign in Niger, January 2006, J. Geophys. Res., 113, D00C10, https://doi.org/10.1029/2008JD009897, 2008. a, b 4. Dey, S., Tripathi, S. N., Singh, R. P., and Holben, B. N.: Retrieval of black carbon and specific absorption over Kanpur city, northern India during 2001–2003 using AERONET data, Atmos. Environ., 40, 445–456, 2006. a, b, c 5. Dong, J., Zhao, J. M., and Liu, L. H.: Morphological effects on the radiative properties of soot aerosols in different internally mixing states with sulfate, J. Quant. Spectrosc. Ra., 165, 43–55, https://doi.org/10.1016/j.jqsrt.2015.06.025, 2015. a
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