Polarimetric radar rainfall estimation in complex orography scenarios

Radar rainfall estimation is a complex process dealing with several error sources, some of them being related to the environmental context. The presence of orographic obstacles heavily affects the quality of the retrieved radar products. In relatively flat terrain conditions dual-polarization has been proven either to increase the data quality or to improve the rainfall estimate. The potential benefit of using polarimetric techniques for precipitation retrieval is evaluated in the present work using data coming from two radar systems operating in Italy in complex orography conditions. Ten days of observations, for a total of 240 hours, were analyzed. In particular, the work is finalized to: i) clutter removal through the synergy of clutter map, radial velocity and polarimetric texture analysis; ii) correction of two-way path attenuation; iii) reconstruction of vertical profile of reflectivity; iv) polarimetric estimate of near-surface rainfall. Several techniques, approaching the previous problems, are inter-compared and evaluated. The accomplished analysis outlines encouraging results that might open new scenarios for operational applications. Indeed, rainfall algorithms using specific differential phase resulted to mostly outperform the examined reflectivity-based retrieval techniques except for the analyzed winter storm. In the latter case the likely contamination by frozen or melting snow tends to degrade the performance of the examined Kdp -based rainfall algorithms.