Rain measurements with SIR-C/X-SAR

Two approaches to rain measurement using the normal configuration of the SIR-C/X-SAR radars are considered. In the first approach, the rain echo is retrieved much as it is for ground-based radars. The second approach is to observe the depth of the shadow created by attenuation through a rain storm. The first approach was used for passes over the central western Pacific Ocean, where the surface echo was weak. The second approach was used for storms discovered serendipitously over the Amazon rain forest, where the surface echo is strong and the shadows are obvious. Retrieved rain rates over the Southwest Pacific were subject to more variability due to the necessary assumptions than rain rates retrieved over the Amazon forest, where fewer assumptions were necessary. (AIAA)