Simulations of mirror image returns of air/space-borne radars in rain and their applications in estimating path attenuation

The mirror, image (MI) rain echo, received through the double reflection of the radar pulse from the surface, may provide useful information in estima ting the rainfall rate from airborne and spaceborne weather radars. However , because of the complicated scattering mechanisms involving the surface an d rain and the relatively small amount of measured data, studies of the MI effect have been few. In this paper, a more rigorous model of the MI return power has been constructed that yields the co- and cross-polarized compone nts of the hll and bistatic returns as a functions of the radar parameters (antenna beamwidth and radar altitude) and the scattering properties of the rain and surface. As a test of the model, the mirror image return, as esti mated from theory, is compared with the measured hll range profile, and rea sonably good agreement is obtained. For meteorological applications, algori thms for estimation of the rain path attenuation are developed based on the difference of the direct and MI returns at the same distance from the surf ace. The accuracies of the algorithms are analyzed and compared with those of the surface reference technique (SRT) through the simulations for airbor ne and spaceborne [the case of the Tropical Rain Measuring Mission (TRMM)] geometries.