Modelling X-band SAR Observations of Precipitating Clouds over Land and Sea Using C-band-dual Polarization Weather Radar

Data collected by weather radars, typically at S, C and X-band frequencies, and in particular those with dual-polarization capabilities are frequently used to investigate observations of precipitation events collected by satellite borne instruments, such as real or synthetic aperture radars operating at different frequencies. Satellite borne SAR aims at providing surface characteristics for different applications in "all weather" conditions. However, precipitation affects SAR images depending on the employed wavelength, and results in attenuation of surface backscattering, additional backscattering from sampled precipitation, geometric and radiometric distortion. At the 9.6 GHz frequency (X band) of the Italian Space Agency Cosmo Sky Med (CSK®) constellation (and by other SARs currently in orbit), attenuation induced by intense precipitation can be significant, masking features of the observed surface. Over land, attenuation prevails over increased backscattering due to precipitation sampled by radar beam, often negligible with respect to terrain backscattering, also influenced by the terrain wetting. Coincident dual polarization radar measurements allow to estimate X band specific attenuations at the frequency and incidence angle of SAR [1][2]. A classification of hydrometeors obtained from weather radar polarimetric signature of precipitation can be used to select the proper algorithms for specific attenuation [3]. Over the sea precipitation induces also changes in the sea NRCS that can be treated by resorting to rainfall fields retrieved by weater radar and a proper modelling [4][5]. Precipitation cases collected in 2 years by the CSK satellites over terrain and sea are analyzed through a model applied to simultaneous observations collected by C-band