利用FY-2C卫星数据反演云辐射特性

本文利用FY-2C静止卫星提供的可见光、中红外和热红外观测数据, 开展了水云光学厚度、粒子有效半径和云顶温度的云参数遥感探测理论和反演方法研究。基于FY-2C可见光、中红外(3.75 μm)与热红外(11 μm)通道辐射率对云光学厚度、 云滴有效半径、云顶温度辐射参数的敏感性分析, 提出三通道同时反演云的光学厚度、云滴有效半径及云顶温度的迭代方案; 通过个例分析进行了云参数反演试验, 并将结果与MODIS的云反演产品进行了对比, 最后对反演误差进行了分析。主要结论如下:(1) 个例反演得到的云参数与各通道探测数据有着较好的对应关系, 迭代计算标准偏差在允许的计算精度范围内(<0.89%), 反演结果具有合理性; (2) 通过与MODIS云反演产品的对比可以看到, 两者云光学厚度、云滴有效半径的均值和直方图分布都非常一致, 而MODIS的云顶温度比FY-2C反演值要高, 考虑到FY-2C的 11 μm通道测量的辐射值与MODIS相比偏小, 因此认为我们的反演方法与MODIS方法的精度是相当的。

Retrieval of Cloud Radiative Properties from FY-2C Satellite Data

This paper describes the theories of remote sensing and algorithms for retrieving cloud radiative properties such as cloud optical thickness, cloud particle effective radius, and cloud top temperature, using multispectral images such as visible, middle-infrared, and far infrared channel reflectance, and brightness temperature from the Visible and Infrared Spin Scan Radiometer (VISSR) sensor of FY-2C satellite. Based on the sensitivity analysis between FY-2C visible, middle-infrared, far infrared channel radiance, and radiative parameters such as cloud optical thickness, cloud particle effective radius, cloud top temperature, surface albedo, and surface temperature by radiative transfer calculations, an iterative algorithm for retrieval of cloud optical thickness, cloud particle effective radius; and cloud top temperature simultaneously by three channels of FY-2C sensor is developed and applied to experimental study. The retrieval results are compared with MODIS cloud products. Finally, the retrieval errors are analyzed. Conclusions are as follows: 1) There is a good correspondence between observed data of FY-2C channels and retrieved cloud parameters, standard deviation (SD) of iterative algorithm is reasonable (0.89%); 2) A comparison with MODIS cloud products shows a good coherence of cloud optical thickness and cloud particle effective radius between FY-2C and MODIS, while the cloud top temperature of FY-2C retrieval results is lower than that of MODIS. In view of lower-valued 11μm channel radiance from FY-2C, the precision of this algorithm is equivalent to that of MODIS.