沙尘气溶胶粒子群的散射和偏振特性

根据Mie散射理论,以对数正态分布函数描述沙尘气溶胶粒子群的粒径尺度分布,计算了沙尘气溶胶粒子群在0.2～40μm波段间对太阳短波辐射和地球大气长波辐射的单次散射反照率、散射相矩阵函数,揭示了不同相对湿度时,沙尘粒子群对入射辐射的散射和偏振的特征。结果表明,沙尘粒子群的单次散射反照率随着入射波长的增加有较大起伏,不同相对湿度条件下,变化趋势基本一致;在可见光、近红外波段单次散射反照率随湿度增加而变大,湿度95%时非常接近于1;大于10μm的热红外波段单次散射反照率随相对湿度增加而减小,具有较强的吸收辐射能力。散射辐射强度受湿度影响较小,随散射角的增加呈现先减小后增大的趋势,且增大的趋势随着波长的增加而减弱;不同波段上,线偏振和圆偏振随散射角和相对湿度变化存在差异;在前向和后向仅对入射辐射为圆偏振辐射产生圆偏振散射;散射光的偏振特性及其湿度差异主要表现在后向散射区,多以拱形形式体现。拱顶峰值散射角位置存在差异,且峰值散射角随相对湿度的降低向后向漂移。

Scattering and Polarization Characteristics of Dust Aerosol Particles

Based on Mie scattering theory, the single scattering albedo and the phase-matrix function of dust aerosol particles during wavelength of 0.2~40 μm for solar radiation and earth-atmosphere long-wave radiation are calculated with the lognormal distribution function to describe the dust particles size distribution. The scattering intensity and polarization characteristics of light scattered by dust aerosol particles are studied at different relative humidity conditions. The results show that, the single scattering albedo has an evident change with the incident wavelength; the variation trend is identical at different relative humidity conditions; within the visible and near-infrared band, the single scattering albedo increases with the increasing relative humidity, it is very close to 1 at relative humidity of 95%; within the thermal infrared band greater than 10 μm, the single scattering albedo decreases with the increasing relative humidity and it has strong ability to absorb radiation. The scattering intensity has less effect on relative humidity and shows a trend of decreasing firstly and then increasing with the increasing scattering angle, the increasing tendency decreases with the increasing wavelength; for the linear and circular polarization of scattered radiation, the change with the scattering angle and relative humidity has different properties at different bands; in the forward and backward scattering directions, it only produces the circular polarization by dust aerosol particles, when it is assumed that incident light is right hand circularly polarized. Polarization properties of scattered radiation and their differences with humidity mainly change in the backward scattering region, where it is as an arched form. The scattering angle for peak point is different at different relative humidities and the peak position drifts to the larger scattering angle with the decreasing relative humidity.