Observations of a severe hail-bearing storm by an operational X-band polarimetric radar in the Mediterranean area

Several experimental studies undertaken in the last decade have outlined the benefit of dual-polarization technique in compensating the major limitation on the use of X-band radars for heavy precipitation measurements, i.e., attenuation. However, despite the generally comforting results in rainfall amount and DSD retrieval, it is trivial to state that any attenuation correction technique cannot overtake the physical limit represented by signal extinction, that can be considered as the main limitation of the quantitative use of a single X-band radar in operational contexts. Potential of X-band dual-polarization radar technique is shown with reference to an intense event occurred on 21 February 2013. That strong convective precipitation event with associated rain-hail mixture flash flooding the city of Catania (Sicily, Italy), observed by the operational X-band dual-polarization radar located in the nearby airport, is analyzed in terms of polarimetric signatures. Absolute and differential attenuation are dealt with differential phase measurements properly processed through an iterative approach using a 2-km moving window. A Bayesian hydrometeor classification algorithm is also adopted to support the analysis of the storm characteristics. Extemporaneous signal extinction caused by close-range hail core causing significant differential phase shift in very short range path is documented. Nevertheless, the localized and nearby peak of precipitation amount was extraordinarily catched using a KDP-based rainfall algorithm.