## 1 Introduction
Satellites equipped with microwave sensors, are a valid tool to provide information about thunderstorms' structure and intensity, especially when they develop over the sea, as it often happens in the Mediterranean area. Microwave radiation has the ability to directly interact with solid and liquid hydrometeors (raindrops, graupel, hail, snowflakes) within the clouds [12; 13; 14], since their sizes are comparable to the microwave radiation wavelength (at frequencies between 10 and 200 GHz). For example, the upwelling radiation measured by passive microwave (PMW) radiometers at the top of the atmosphere is the result of the background emission signal (surface and atmospheric gases) modulated by the cloud hydrometeors-radiation interactions within the cloud and, therefore, can be related to the precipitation structure. On the other hand, the backscattering signal measured by a spaceborne precipitation radar is the result of reflected echoes by the hydrometers within a given volume. This explains the great attention that microwave spaceborne instruments have acquired over the years for scientific and operational purposes. With the advent of the Tropical Rainfall Measurement Mission (TRMM) in 1997, it has been possible to study deep convective systems over tropical and subtropical areas by means of co-located active and passive microwave observations [15; 16; 17; 18; 19]. More specifically, hailistorms and severe deep convection penetrating the tropopause over the tropics and on global scale have been analyzed by means of measurements of passive microwave sensors onboard different platforms [20; 21; 22; 23; 24; 25]. The Global Precipitation Measurement-Core Observatory (GPM-CO), launched on 27 February 2014 and covering latitudes up to 65 \({}^{\circ}\)N/S, has started a new era not only for precipitation monitoring, but also for the analysis and characterization of precipitation events around the globe. In the present study, we aim at demonstrating the unique capabilities of the GPM-CO in the analysis of the climatology of deep convective systems in the Mediterranean area (i.e., seasonal and diurnal cycles, as well as geographical distribution), and to reveal how this region is often hit by extremely severe deep convection phenomena, also over the sea, with similar characteristics to those found in the tropics (e.g., Reference [26; 27; 28]). The GPM-CO is equipped with the two most advanced active and passive microwave sensors designed for precipitation retrieval from space: the Japan Aerospace Exploration Agency (JAXA) Dual-Frequency Precipitation Radar (DPR), and the National Aeronautics and Space Administration (NASA) GPM Microwave Imager (GMI) conically-scanning radiometer [29; 30]. The DPR allows study of the three-dimensional structure of the precipitation and its microphysics parameters, while the multichannel GMI microwave measurements, available at unprecedented spatial resolution up to 5 km, allow for inferring information on precipitation microphysics processes. Detailed information provided by these two sensors has been exploited in several studies on the analysis of different typologies of deep convective systems on a global scale [26; 27; 28] but without focusing specifically on the Mediterranean area. In particular, passive microwave measurements, by combining observations of TRMM and GPM-CO, or of different GPM constellation radiometers (including the GMI), have been used globally to identify the scattering signature of hail in intense thunderstorms, observed as a strong depression of upwelling brightness temperatures measured by satellite radiometers [31; 32; 33]. Over the Mediterranean region, a climatological analysis of deep convection has been carried out by Reference [34] using long-term measurements of the Advanced Microwave Sounding Unit-B/Microwave Humidity Sounder (AMSU-B/MHS) cross-track scanning radiometer measurements.