Variabilité et structure des précipitations au Sahel, apport des radars météorologiques et des réseaux hertziens commerciaux

Le résumé fourni par la source

In West Africa, rainfall is an essential element for the economic growth of countries and their populations. Driven by a monsoon regime, rainfall is concentrated from May to October. Depending on their intensity and their spatial and temporal distribution, they can lead to the development of rain-fed agriculture, but also lead to food, economic and human losses when they cause severe flooding. In the context of current and future climate change, the region is expected to be more frequently affected by extreme events. This thesis contributes to provide elements to improve the quality of precipitation estimates in a poorly instrumented region of the world. Measurements from the MIT weather radar, deployed during the AMMA 2006-2007 campaign in Niamey, are treated following two methodological approaches in order to extend quantitative precipitation estimates (QPE) beyond the AMMA-CATCH rain gauge network. Rainfall measurement is also addressed using the telecommunication links of cell phone operators. For the first time in West Africa, the method is validated on a microwave link northeast of Ouagadougou by comparison with a rain gauge and Xport radar. Over the two months under consideration, 95% of the cumulative rainfall was estimated using this method, with a low number of false alarms or non-detections. At the scale of the event, the results are mixed depending on the events.Furthermore, in order to document the icy microphysics of mesoscale convective systems (MCS) in the Sahel, the polarimetric measurements of the Xport radar were also used to validate the particle identification algorithm (HID). The estimated solid particle distributions, in terms of graupels and aggregates, were compared with in situ measurements acquired during instrumented flights performed during the Megha Tropics pre-validation campaign in Niamey in August 2010. Synthetic variables, obtained by a T-matrix modeling from shape and density characteristics measured by the airborne probes during the flights, confirmed these results.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.