当云层的温度在－40℃~0℃之间时, 云层中会存在冰和水两种相态的云滴, 其散射特性与纯水云以及纯冰云特性有较大差异, 因此遥感反演混合相云层的微观和宏观物理特性具有重要的意义。本文采用冰水双层球模型模拟了冰水混合云中的云滴, 利用Mie理论计算了纯水、纯冰和冰水颗粒的单次散射特性, 分析了单次散射相函数, 不对称因子, 单次散射反照率等随着有效半径、相态、内外半径比等的变化特性。利用离散纵标法(DISORT)计算了水云和冰云对0.75 μm、2.16 μm和3.3 μm的双向反射函数, 讨论了利用纯水滴和纯冰滴反演冰水混合云滴的误差。分析结果表明, 利用0.75 μm和2.16 μm的太阳光反演冰水混合云的光学厚度和有效半径时, 光学厚度误差较大, 有效半径误差较小; 结合0.75 μm和3.3 μm的太阳光反演冰水混合云的光学厚度和有效半径时, 光学厚度误差较小, 有效半径误差较大, 其会高估其有效半径; 另外结合0.75 μm和3.3 μm这两个波长的反射函数反演冰水云的冰水混合比更为有效。

Both ice and water phase particles may coexist in clouds when the temperature is between －40℃ and 0℃. The scattering characteristics of the mixed-phase clouds are deeply different with the pure water or ice phase clouds. So, it is an important problem to derive cloud microphysical and macrophysical properties for mixed-phase clouds. The clouds particles of mixed-phase clouds are modeled by two-layer sphere particles. Based on the Mie theory, the single scattering phase function, asymmetric factor, single scattering albedo are computed with the changing of the effective radius, thermodynamic phase and the ratio of the inner and outer radius. The reflection function of the pure water phase clouds and pure ice phase clouds are calculated with the DISORT method at the wavelength 0.75 μm、2.16 μm and 3.3 μm. The influence of the mixed-phase clouds droplets to the retrieval of the cloud microphysical is discussed. The analyses suggest that the errors of the effective radius inferred for mixed-phase is small with the combination of the wavelength 0.75 μm and 2.16 μm if pure liquid or pure ice phase is assumed for the cloud, but the error of the optical thickness is bigger. On the contrary, the errors of the optical thickness inferred for mixed-phase is small with the combination of the wavelength 0.75 μm and 3.3 μm if pure liquid or pure ice phase is assumed for the cloud, but the effective radius can be overestimated. Combination the reflection of wavelength 0.75 μm and 3.3 μm can be effectively used to infer the mixing ratio of water ice in the mixed-phase cloud.