风云静止卫星双星立体观测云顶高度反演初步研究

推导出利用风云静止卫星双星视云坐标计算云下点坐标和云顶高度的理论算法，对静止双星865E/104.5E和86.5E/112E两种组合观测条件下视云位移分布特征以及视云位移与云高关系进行分析计算，在此基础上，提出一种可以实现全区域高精度立体云高反演的非线性视云位移云高反演模型。结果显示，观测数据空间分辨率0.01°条件下，两种双星组合云高分辨率平均值分别为1.28 km和0.93 km，表明86.5E/112E组合反演精度优于86.5E/104.5E组合。最后，利用FY2D和FY2F双星数据在西北太平洋进行立体云高反演实验，并将反演结果与Cloudsat卫星微波雷达云高测量数据进行对比分析。

A Study of Cloud Top Height Retrieval from FY-2 Stereoscopic Observation

We firstly derive the algorithm to retrieve the true cloud location and cloud top height by use of the FY2 stereoscopic observation, and the algorithm to compute the apparent cloud parallax from the true cloud location and its cloud top height. Based on the geostationary satellite stereoscopic algorithm, a simulation is performed on the distribution feature of the apparent cloud parallax and the relationship between the apparent cloud parallax and the cloud top height under two cases of FY2 stereoscopic observation. The analysis shows that the linear model may cause larger errors that cannot be ignored near the conjugate region edge. We accordingly propose a nonlinear cloud height retrieval algorithm which could be used on the full region of stereoscopic observation. The average height resolution is about 1.28 km for 86.5E/104.5E and 0.93 km for 86.5E/112E, when the spatial resolution of the applied data are both 0.01 degree. The combination of 86.5E/112E has better height resolution than 86.5E/104.5E. A stereo cloud height retrieval test is performed to a case from the northwest Pacific and the test results are compared with the CTH observed by Cloudsat CPR microwave radar.