后向散射系数模型及其对雨强反演精度的影响

Backscattering coefficient model and its application in rain rate retrieval

对典型地表条件下后向散射系数σ0的观测分析有着非常重要的意义,它能够为降水的反演提供巨大的便利。但是由于σ0会受到外界条件的影响而变化,给σ0的使用带来了不便。为此,通过对2002～2005年间TRMM/PR的2A21数据统计分析,获得晴空条件下地表后向散射系数σ0的变化规律,并在此基础上提出晴空三种典型地表条件下(海洋、沙漠、热带雨林)的σ0均值模型,希望给未来降雨反演带来便利。最后利用kZS算法检验了该均值模型对降雨反演精度的影响。由反演结果可以看出,利用σ0的均值模型在地表条件相对均一的海洋、沙漠地区都获得了很好的反演效果,尤其是海洋地区可以在一个相对更大的范围内使用,而在热带雨林地区,只能在一个相对较小的区域内使用。

The study of backscattering coefficient （σ^0） of representative land surface is of great importance. It can not only be used for the calibration of spaceborne/airborne instruments, but also be a great help to rain rate retrieval. But it varies with time and space and it isn＇t easy to use. In this paper, with TRMM/PR 2A21 data （from year 2002 to 2005）, three kinds of representative land surface （ocean, desert, rainforest） are selected and their annual and seasonal changes of σ^0 are investigate. Then an average σ^0 model is suggested. In order to find out whether the model can represent the real σ^0 variation, the kZS algorithm is used to test. And the rain retrieval result is pretty good. Especially over ocean and desert, the model can be used in a large area.