## 4 Discussion and Conclusions  
The analysis carried out in this work allows highlighting of the characteristics of deep convective systems in the Mediterranean area, based on the unique and unprecedented measurements provided by the GPM-CO active and passive microwave sensors. Despite the availability of a limited number of satellite overpasses and the limited swath size (245 km for the radar-based PF dataset used in this study), the results obtained seem to correspond to the main characteristics of deep convection systems, and, in particular, evidence similarities with previous studies based on GPM-CO measurements at global scale, or in other areas of the world. The PF categorization based on the intensity of each main convection proxy allows extraction of the precipitation structures that have extreme values for the selected variable. By adopting the categorization based on the top percentages of proxy value distributions (0.01, 0.1, 1, and 10%), the geographical, diurnal, and seasonal analysis is carried out without relying on thresholds obtained from previous studies, with other sensors, or in other areas of the globe (e.g., Reference [16; 19; 26]). It is clear that the thresholds found for each category will never be univocal, since they will depend on the distribution itself, being determined a posteriori from the percentiles. The small deviations of the diurnal and seasonal trends of each single property is linked to the diversity of the subsets of the selected PFs, based on the chosen parameters: what is important is not the exact overlap of the trends, but the great similarities of distributions obtained using both radar- and radiometer-based properties. The diurnal variability shows a strong afternoon maximum of PF occurrence over land, where a 10-12% of the PFs belonging to the top intense 1% of each proxy distribution is found between noon and 7 p.m. local time. Weaker diurnal variability is observed over sea, with shallower peaks during the night. The maps of seasonal patterns show clear differences in the geographical distribution of deep convection PFs, pointing out the crucial role that the solar radiation has in affecting the daytime occurrence of intense PFs. Therefore, different origins of severe convection are expected in the cold and in the warm season. Namely, in the fall, severe convection is favored by strong instability induced by the cold air over warm water surface, while, in winter, we expect a direct relationship with the extra-tropical cyclones. The cold air above cool sea water does not lead to a strong instability till late spring when the sea surface temperature has a significant increase. In summer, the trends are a direct consequence of different heat fluxes between the land/sea surface and the atmosphere, due to the greater latent heat capacity of the sea compared to the land surface. The heat flux favors the convective diurnal activity exploiting the destabilization of the air column produced by the orography. It emerges that deep convection follows the general atmospheric circulation during the year, with a general southward shift, that begins in autumn and becomes more visible in winter. Particularly, in winter, the number of PFs found on the basis of different criteria generally decreases substantially for each parameter. It is clear how a key role in the periodic location of severe weather episodes is also played by synoptic conditions linked to the general atmospheric circulation, as well as by the seasonality of solar radiation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**OPFs** & **Spring** & **Summer** & **Autumn** & **Winter** \\ \hline Land & 7.6\% & 21.4\% & 12.1\% & 1.7\% \\ Sea & 3.6\% & 4.0\% & 11.4\% & 5.6\% \\ \hline
**Hailstorms** & **Spring** & **Summer** & **Autumn** & **Winter** \\ \hline Land & 4.5\% & 18.6\% & 12.0\% & 1.1\% \\ Sea & 2.6\% & 3.9\% & 12.0\% & 4.1\% \\ \hline \hline \end{tabular}
\end{table}