Upper Troposphere Lower Stratosphere structure during convective systems using GPS radio occultations

The deep convective systems play a fundamental role in atmospheric circulation and climate. Thunderstorms and meso-scale convective systems produce fast vertical transport, redistributing water vapor and trace gases and influencing the thermal structure of the upper troposphere and lower stratosphere (UTLS) contributing to the troposphere-stratosphere transport and affecting the Earth global circulation and the climate changes. 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 this thesis is tounderstand if the radio occultation technique can be used to study the water vapor in the UTLS, and to characterize the convective processes. The contribution to the analysis of tropical storms for the future mission ACES will also be evaluated.
Using data from the past and ongoing GPS RO missions we have defined an algorithm to detect the clouds top of the convective systems and their thermal structure. Other satellite and in-situ measurements co-located with GPS ROs, were used to validate the results.
The outcomes are very promising. The GPS signal can be used to characterize the thermal structure of the convective systems, and to detect the storm cloud top. The RO signal contains interesting information in connection to the troposphere–stratosphere transport providing a clear signature of these processes on the atmosphere.
However the signal is not sensitive enough to detect the variation of water vapor in the UTLS.
The ongoing GPS RO missions do not provide a suitable Earth coverage in order to allow a systematic study of convective systems and an increase of soundings in the tropical area is requested to exploit all the capabilities of thistechnique.