Modelling polarimetric effects of precipitation on spaceborne side-looking aperture radar response

Precipitating clouds can have significant effects on both amplitude and phase of the signal received by spaceborne microwave sensors, especially if operating at frequencies above C-band. The evaluation of these effects is more complicated on Synthetic Aperture Radar (SAR) systems, due to their slant observing geometry. The signal received by spaceborne SAR systems in presence of precipitating cells is a combination of surface and volumetric scattering, reduced by path attenuation and largely dependent on frequency, polarization and spatial distribution of hydrometeors. Moreover, the nominal SAR resolution (of the order of meters) is reduced (to the order of hundreds meters) due to the random nature of the moving distributed atmospheric target. In this work a numerical forward model of spaceborne SAR response due to precipitating clouds is introduced, using a high-resolution mesoscale atmospheric numerical model. This modelling framework aims at improving the understanding of the correlation between SAR retrieved signals and precipitation contents. The developed simulator, quite flexible in terms of structure and configuration, is suitable to analyze X, Ku or Ka spaceborne observations, adopted for several current or planned spaceborne SAR missions.