Precipitation signature on side-looking aperture radar imaging: Sensitivity analysis to surface effects at C, X and Ku band

Previous studies have shown the potentiality of X-band synthetic aperture radar in measuring rainfall. A microwave forward model describes the Normalized Radar Cross Section (NRCS) as composed by a surface contribution and a volumetric contribution and inversion techniques were used to derive the precipitation over land, particularly over bare soil. However, different surfaces may affect the SAR precipitation signature, so here, we present a sensitivity analysis to the surface effects for three different frequencies such as C-, X- and Ku-band using a two-layer precipitating cloud system composed by rain and snow. Particular attention is given to the effects of sea surface whose variability is strongly related to the surface winds. The main results show that as the frequency increases, the NRCS increases. Moreover, when the wind speed becomes higher, the SAR response due to precipitation is mainly influenced by the surface contribution so that the sensibility to precipitating cloud decreases. This behaviour can be ascribed to the increasing sea surface roughness.