Simulation of Beam Filling Effect on Spaceborne Precipitation Radar Rainfall Retrieval

In order to estimate rain rate quantitatively, the parameters measured by a spaceborne precipitation radar are usually assumed to be uniform within the antenna beam. It means that the rainfall spreads uniformly within a range of a few kilometers. However, in most cases of convective rain, the footprint size of spaceborne radar may be larger than the rain cell size, then the reflectivity and the path integrated attenuation are not accurate due to nonuniform beam filling. As a result, the retrieved rain rate is also biased. In this paper, beam filling effects on spaceborne precipitation radar are investigated theoretically according to whether rain attenuation can be neglected. Furthermore data from the Airborne Rain Mapping Radar are used to simulate observations from spaceborne precipitation radar with different beam width.