云-气溶胶相互作用是气候变化研究中的热点和难点问题。晴空条件下气溶胶直接辐射强迫评估已有较大进展，但有云情况下气溶胶直接辐射强迫的评估不确定性仍很大。目前研究面临的主要问题是缺乏云天时的气溶胶观测资料，因为绝大多数卫星遥感都先将云剔除，只给出晴空区的气溶胶特性，不能提供云天时气溶胶和云的特性。A-Train卫星编队包括PARASOL偏振成像仪、MODIS中分辨率成像仪以及CALIOP星载激光雷达，具备主被动准同步联合遥感能力，为改进气溶胶遥感算法和同时反演云、气溶胶特性提供了契机。鉴于此，本项目拟联合利用上述主被动卫星观测资料，用最优统计理论发展晴空、云天（层云上存在气溶胶）和云-晴空过渡区条件下，气溶胶和云微物理特性同时反演的方法，并对反演结果加以验证。研究结果将为偏振传感器的仪器指标性能评估和资料处理提供理论依据，也将进一步提高对气溶胶辐射和气候效应的认识。

Aerosol-cloud interactions have been one of difficulties and hot issues in the study of the climate change. Improvements on the estimation of the clear-sky aerosol direct radiative forcing has been substantial with availability of aerosol optical properties from the ground-based and satellite remote sensing. The uncertainties in the cloudy-sky aerosol radiative forcing remain large due to the lack of cloudy-sky aerosol properties measurements. It is common to distinguish "cloudy" and "cloud free" areas at the first step when deriving the aerosol properties from remote sensing measurements. However, it is necessary to make simultaneous retrieval of aerosol and cloud properties from satellites in order to quantify the aerosol and cloud effects on climate. The "A-train" satellite constellation allows a synergetic use of PARASOL, with MODIS/AQUA to obtain the spatial information on the cloudy parameters, and with CALIOP to get the accurate information on cloud/aerosol layer height and thickness. The proposed work aims to explore the capability of combining the active- and passive- satellite measurements for simultaneous retrieval of aerosol and cloud microphysical properties in clear and cloudy sky by using the statistical optimized theory and validate the retrieval results. The study can give reference for the instrument performance evaluation and data processing of the current and future polarization sensor. In addition, the study results will improve the undestanding of aerosol-radiation-climate effects.