The deep convective systems play a fundamental role in atmospheric circulation and climate. Thunderstorms and mesoscale convective systems produce fast vertical transport, redistributing water vapor and trace gases and influencing the thermal structure of the Upper Troposphere - Lower Stratosphere (UTLS). These processes influence the climate and create damages and lives loss. The determination of cloud top height and the thermal structure of the system are important for the understanding of the climate effect and to detect and forecast the strength of the storm.The ongoing satellite missions do not provide suitable time/space coverage to study such kind of phenomena with adequate horizontal and vertical resolution and sensitivity. The ground based measurements and campaigns are too sparse and the acquisitions at the UTLS altitudesare always difficult and sometimes not reliable.The Global Positioning System (GPS) Radio Occultation (RO) technique enables measurement of atmospheric density structure in any meteorological condition, with extremely high accuracy, precision and vertical resolution, providing a global coverage of the Earth. The objective of the proposal is to combine the capabilities of the GPS RO technique with the high temporal resolution of ground based instruments, with the spatial resolution of other satellite instruments and with the accuracy and precision of campaigns measurements, to define a solid algorithm detecting the storm cloud top with high accuracy using the RO profiles. This will allow to get a good understanding of the role of convection in determining the thermal structure and composition of the UTLS both in the tropics and in the extra-tropics, and to improve the forecast of theintensity of severe events. The analysis of the temporal and zonal variation of the GPS signal will also be used to analyze the climate changes and the contribution of the convection to the climate changes.