地基红外高光谱辐射仪和偏振激光雷达联合反演薄云微物理参数

Thin clouds play a role that cannot be ignored in the Earth’s radiative budget, global climate change and military weather service. Because these clouds are featured with low LWP, optical thin, often broken and potentially mixed phase, it is challenging to accurately retrieve their microphysical properties. Some studies suggest that the ground-based hyperspectral infrared sounder has advantage in the thin clouds measurement. However, there are still some unsolved problems. For example, the interference effects from aerosols below clouds, the reliability issue of cloud phase discrimination, and the uncertainty relationship between the microphysical properties of clouds and the measured radiation. To address these problems, the project will consider the theory and method to retrieve microphysical properties of thin clouds from combined ground-based hyperspectral infrared sounder and polarization lidar. A solution to calculate the cloud emissivity considering aerosol effect will be first studied, then the contribution of emissivity spectra and lidar depolarization ratio to cloud phase classification will be discussed by a series of simulations. The phase determination algorithm will be developed based on support vector machines. The complementarities and restrictions on the use of cloud boundary, cloud optical depth and cloud particle shape derived from polarization lidar will be studied to retrieve microphysical properties of thin clouds by ground-based hyperspectral infrared sounder. The algorithms including a restricted lookup table strategy and a variational scheme for retrieving cloud optical depth and effective radius will be finally proposed. This project will provide an efficient retrieval method for thin cloud measurement by integrated ground-based sensors, which has important theoretical significance as well as application value.

薄云对地球辐射收支、全球气候变化以及军事气象保障均有不可忽略的重要意义，其含水量低、光学厚度小、形状破碎且可能存在混合相态，目前很多测量手段难以对其微物理参数进行有效测量。利用地基红外高光谱辐射仪探测薄云有一定优势，但仍然存在气溶胶的干扰问题、云相态判别的可靠性问题以及反演关系的不确定性问题。本项目拟研究利用地基红外高光谱辐射仪和偏振激光雷达联合探测薄云的的理论与方法。具体包括建立考虑气溶胶影响的云发射率计算方法；研究云的发射率光谱和激光雷达线性退偏振比对云相态分类的贡献，实现基于支持向量机的薄云相态的综合判别；充分考虑偏振激光雷达数据中含有的云边界、光学厚度、云滴形状等信息对地基红外高光谱反演云参数的补充和约束能力，发展基于多约束查找和基于一维变分的薄云光学厚度和有效粒子半径的联合反演方法。本研究将为薄云的地基遥感观测提供一种有效的联合观测手段，具有重要的理论意义和应用价值。

薄云对地球辐射收支、全球气候变化以及军事气象保障均有不可忽略的重要意义，其含水量低、光学厚度小、形状破碎且可能存在混合相态，目前很多测量手段难以对其微物理参数进行有效测量。本项目围绕地基红外高光谱辐射仪和偏振激光雷达联合反演薄云微物理参数进行了科学研究。主要研究内容包括建立考虑气溶胶影响的云发射率计算方法、实现基于支持向量机的薄云相态判别方法、发展薄云光学厚度和有效粒子半径的联合反演方法。主要成果有：（1）建立了地基傅里叶红外高光谱辐射计正向模拟系统并评估了气溶胶对红外高光谱辐射的影响；（2）开展了气溶胶散射特性模拟计算方法研究和气溶胶消光系数廓线反演与比对工作；（3）提出了云层发射率的地基联合反演方法并进行了结果验证；（4）建立了基于支持向量机的地基红外高光谱辐射计和激光雷达联合进行云相态判别的方法；（5）发展了联合地基红外高光谱辐射计和激光雷达反演云滴有效半径和云水路径的方法；（6）提出了基于地基红外高光谱辐射数据进行大气背景廓线反演新方法。本研究为薄云的地基遥感观测提供一种有效的联合观测手段，具有重要的理论意义和应用价值。