Models for the optical simulations of fractal aggregated soot particles thinly coated with non-absorbing aerosols

作者:Wu, Y (Wu, Yu)[ 1 ] ; Cheng, TH (Cheng, Tianhai)[ 1 ] ; Zheng, LJ (Zheng, Lijuan)[ 1 ] ; Chen, H (Chen, Hao)[ 1 ]

JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER

卷: 182  页: 1-11

DOI: 10.1016/j.jqsrt.2016.05.011

出版年: OCT 2016

摘要

Light absorption enhancement of aged soot aerosols is highly sensitive to the morphologies and mixing states of soot aggregates and their non-absorbing coatings, such as organic materials. The quantification of these effects on the optical properties of thinly coated soot aerosols is simulated using an effective model with fixed volume fractions. Fractal aggregated soot was simulated using the diffusion limited aggregation (DLA) algorithm and discretized into soot dipoles. The dipoles of non-absorbing aerosols, whose number was fixed by the volume fraction, were further generated from the neighboring random edge dipoles. Their optical properties were calculated using the discrete dipole approximation (DDA) method and were compared with other commonly used models. The optical properties of thinly coated soot calculated using the fixed volume fraction model are close to (less than 10% difference) the results of the fixed coating thickness model, except their asymmetry parameters (up to 25% difference). In the optical simulations of thinly coated soot aerosols, this relative difference of asymmetry parameters and phase functions between these realistic models may be notable. The realizations of the fixed volume fraction model may introduce smaller variation of optical results than those of the fixed coating thickness model. Moreover, the core-shell monomers model and homogeneous aggregated spheres model with the Maxwell-Garnett (MG) theory may underestimate (up to 20%) the cross sections of thinly coated soot aggregates. The single core-shell sphere model may largely overestimate (up to similar to 150%) the cross sections and single scattering albedo of thinly coated soot aggregates, and it underestimated (up to similar to 60%) their asymmetry parameters. It is suggested that the widely used single core-shell sphere approximation may not be suitable for the single scattering calculations of thinly coated soot aerosols. (C) 2016 Elsevier Ltd. All rights reserved.

通讯作者地址: Cheng, TH (通讯作者)

Chinese Acad Sci, State Key Lab Remote Sensing Sci, Inst Remote Sensing & Digital Earth, Beijing 100864, Peoples R China.

地址:

[ 1 ] Chinese Acad Sci, State Key Lab Remote Sensing Sci, Inst Remote Sensing & Digital Earth, Beijing 100864, Peoples R China