Intercomparison of inversion techniques to retrieve surface rain-rate from SSM/I over the Mediterranean basin by using a 9-year validation set

The skill of some algorithms, based on both a physical and an empirical approach, to estimate surface rain-rate in the Mediterranean region from the special sensor microwave imager (SSM/I) data is analysed. A reliable validation set consisting of rain-gauge data collected throughout 9 years is used to perform such analysis. We aim to confirm the validity of the physical approach adopted in previous works, showing that its behaviour is similar to the one presented by the algorithms based on an empirical approach, but with the well-known advantage of an easy extension to zones different from the calibration one and to sensors operating at other frequencies. We also evaluate the improvement that can be obtained using local scale algorithms rather than global scale ones.