Convectively and orographically driven precipitation study – COPS-France

In spite of a strong societal demand for quantitative precipitation forecasting (QPF), progress in this field has been very slow during the last two decades. While many aspects of numerical weather forecasting have made great advances, model skills for precipitation remain much lower than for other atmospheric parameters. In this context, the German Research Foundation (DFG) decided to launch an ambitious programme aiming to make decisive progress in terms of QPF. A key element of this programme is the organization of a 3 month international field campaign COPS (Convective and Orographically-induced Precipitation Study). COPS will take place in summer 2007 in south-western Germany and eastern France. The selected area covers about 250 km in west-east direction and 170 km from south to north. It includes different low-mountain ranges: the Vosges, the Black Forest and the Swabian Jura. The area is particular prone to high convective precipitation in summer (50% of the days), including severe thunderstorms. Such a project requires a joint effort of the scientific community and necessitates strong international cooperation. This ANR proposal deals with the French contribution to COPS. It includes the participation of experimental teams able to deploy additional key instruments and modelling groups involved in the research field of QPF. The proposal is structured in five work-packages. WP1, WP2, and WP3 are process study oriented. They deal respectively with the initiation of the convection, the aerosols and cloud microphysics, and the life cycle of the convection in its precipitating phase. WP4 is focussing on data assimilation whereas WP5 describes the instrumentation that will be deployed in the field in complement to a large international effort. The methodology is based upon the cross-checking of a unique data set, allowing a full four dimensional mapping of the atmospheric state, with the output of advanced numerical modelling and assimilation systems running at very high-resolution. The following results are expected : • An improved understanding of the physical processes governing orographically-driven precipitation • A better apprehension of QPF errors and the development of rational methods to reduce them • Further progress in cloud and precipitation modelling • A strong impulse in the validation of the AROME modelling and assimilation system before its operational use • A more efficient transfer of “know-how” between Météo-France and academic research • The availability of the AROME assimilation system to the research community • Lessons for the design of future routine observing systems • A reinforcement of the German-French cooperation in the field of atmospheric sciences and weather forecasting