可见光波段非球形沙尘气溶胶散射和辐射特性的理论模拟

Theoretical Simulation of Scattering and Radiative Properties of Nonspherical Dust Aerosols at Visible Wavelength

将非球形沙尘气溶胶视为具有一定尺度谱和形状分布的随机取向椭球粒子群,利用T矩阵和改进几何光学方法模拟了非球形沙尘气溶胶粒子在可见光波段(0.47μm)的散射特性,并与实验室测量结果和等体积球形粒子的计算结果进行了比较。结果表明:利用具有一定尺度谱和形状分布的随机取向椭球粒子模拟自然界中的非球形沙尘粒子散射特性是行之有效的;用等体积球形粒子得到的单散射相矩阵(特别是单散射相函数)与椭球粒子相比,具有明显的差异,而粒子形状对单散射反照率、不对称因子和消光效率的影响明显偏小。通过比较椭球和球形沙尘气溶胶在可见光波段的辐射特性说明在计算非球形沙尘气溶胶辐射特性过程中应考虑粒子形状对其单散射特性的影响。

With the assumption that nonspherical mineral dust aerosols are considered to be a mixture of randomly oriented spheroidal particles with particle size and shape distributions, the scattering properties of nonspherical mineral dust aerosols at visible wavelength （0.47 μm） are theoretically simulated based on the T-matrix method and improved geometric optics method （IGOM）. The corresponding results related to laboratory measurements and equal volume spherical particles are also presented for comparison. The results indicate that it is feasible to simulate the scattering properties of nonspherical dust aerosols by considering dust particles to be a mixture of randomly oriented spheroidal particles with particle size and shape distri- butions, and the differences between equal volume spherical particles and spheroidal particles are obvious for single scattering phase matrix （especially single scattering phase function） when compared with the differences associated with single-scattering albedo, asymmetry factor and extinction efficiency. Moreover, by comparing the radiative properties of dust aerosols at the visible wavelength for spheroid and sphere particle shape as- sumption, it is found that the effect of particle shape on the single scattering properties cannot be neglected in simulating the radiative properties of nonspherical dust aerosols