光学学报, 2016, 36 (8): 0829001, 网络出版: 2016-08-18   

沙尘气溶胶粒子模型的线退偏比特性

Linear Depolarization Ratios Characteristics of Dust Aerosol Particles Model
作者单位
南京信息工程大学大气物理学院中国气象局气溶胶与云降水重点开放实验室, 江苏 南京 210044
摘要
利用离散偶极子近似法研究了旋转椭球体沙尘气溶胶粒子模型在尺度参数变化范围为0.1~23时(波长0.55 μm对应有效半径为0.01~2 μm)的线退偏比特性。通过分析比较不同轴半径比时线退偏比特性的差别,研究了粒子非球形性程度对单分散和多分散沙尘气溶胶粒子退偏比特性的影响。对单分散系,旋转椭球体沙尘气溶胶的线退偏比在瑞利散射区和米散射区随散射角的变化有不同的分布特征;在瑞利散射区,散射角分别为0°和180°的前后向散射方向,线退偏比较小,其值在1%的量级,而在散射角为90°附近的侧向,线退偏比有最大值,可达100%;在米散射区,线退偏比则无明显的极值分布,但有明显的后向增强;单分散沙尘粒子明显的非球形性特征,会增加在瑞利散射区的线退偏比,但却不会明显增加米散射区的线退偏比。而对多分散系,除了出现线退偏比最大值的侧向附近(80°~100°)之外,沙尘粒子非球形性特征越明显,其线退偏比越大。
Abstract
Linear depolarization ratios (LDR) characteristics of spheroid dust aerosol particles are studied based on discrete dipole approximation (DDA) for size parameters from 0.1 to 23 (corresponding to effective radius from 0.01 μm to 2 μm at wavelength of 0.55 μm). The effects of the particle asphericity degree on the LDRs characteristics for both monodisperse and polydisperse dust aerosols are performed by comparing LDRs characteristics at different spheroid aspect ratios. For monodisperse particles, the LDRs of spheroid dust aerosol have different behaviors as a function of scattering angle in the Rayleigh and Mie domains. In the Rayleigh domain, the LDRs are small with a value of 1%, in the forward- and backward-scattering directions with the scattering angles of 0° and 180°. While the LDRs show maxima of 100%, at side-scattering angles of 90°. In the Mie domain, the LDRs have no obvious extremum distribution, and reveal significantly enhanced backscattering values. The degree of asphericity of monodisperse dust particles generally increases their LDRs in the Rayleigh domain but not in the Mie domain. However, for polydisperse particles, the degree of dust asphericity increases with the LDRs except in the side-scattering regions (80°~100°) where the LDRs reach maxima.

张小林. 沙尘气溶胶粒子模型的线退偏比特性[J]. 光学学报, 2016, 36(8): 0829001. Zhang Xiaolin. Linear Depolarization Ratios Characteristics of Dust Aerosol Particles Model[J]. Acta Optica Sinica, 2016, 36(8): 0829001.

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