Impact of rainfall incoherent backscattering upon radar echoes above 10 GHz

Radar observations of precipitation profiles from space are simulated in or der to evaluate the impact of precipitation incoherent backscattering upon radar returns above 10 GHz at nadir. Spaceborne and airborne radar frequenc ies at 13.8, 24, and 35 GHz are chosen for carrying out simulations at nadi r. Realistic precipitation profiles are extracted from a microphysical meso scale cloud model simulation and averaged with respect to classes of surfac e rainrate. The classical radar equation is reformulated taking into accoun t the multiple scattering phenomenon through a general definition of the ap parent reflectivity. Numerical results show that opposite effects are due t o the combination of path attenuation and multiple scattering. When first-o rder scattering approximation holds, path attenuation is the predominant co ntribution and tends to reduce the equivalent reflectivity, while multiple scattering tends to increase it, especially in the cloud regions characteri zed by large albedo. For intense rainfall cases the rainrate profiles can b e significantly overestimated when derived from apparent radar reflectivity simply corrected by two-way single-scattering path attenuation. (C) 2000 E lsevier Science Ltd. All rights reserved.