前向小角度的散射辐射分布与散射介质的粒子大小和光学厚度有关。基于一种新型变视场光度计,测量不同天气条件下的前向小角度散射比值、大气光学厚度τ和气溶胶粒子的Angstrom指数α,并与DISORT方法模拟结果进行对比分析。研究结果表明:散射比值随光学厚度的增大而增大;但当光学厚度τ <1时,散射比值取决于粒子有效尺度,粒子尺度越大,散射比值越小。卷云冰晶尺度较大时 (D_e>10 μm),其散射比值小于气溶胶粒子和水云,这为区别薄卷云与气溶胶提供了一种新方法。给出一种提取卷云光学厚度的简单方法,证明了卷云的消光系数在短波段与波长无关。以上研究为地基探测大气特性提供了一定参考价值。

The distribution of forward small-angle scattering radiation is related to the particle size and optical thickness of the scattering medium. The forward small-angle scattering ratio, atmospheric optical thickness τ and the Angstrom index α of aerosol particles are measured based on a new type of variable field photometer under different weather conditions. The results are compared with the results of DISORT simulation. It is shown that the scattering ratio increases with increasing of optical thickness. However, when the optical thickness is less than 1, the scattering ratio would depend on the effective scale of the particle. The larger the particle, the smaller the scattering ratio. When the size of cirrus ice crystal is larger (De>10 μm ), the scattering ratio is smaller than that of aerosol particles and water clouds. This provides a new method to distinguish thin cirrus clouds with aerosols. A simple method for extracting optical thickness of cirrus clouds is presented. It is proved that the extinction coefficient of cirrus clouds is independent of wavelength in short wavelength band. The research provides a certain reference for ground based detection on atmospheric properties.