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Communication incl. Poster: BibTeX citation key:  Caminade
Caminade, C., Ruti, P. M., Doblas-Reyes, F. & Morse, A. P. 2009. A Multi-Model reliability study over the Sahel: from seasonal forecasting to climate simulations. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-09-10 16:40:56
Categories: Monsoon system and its variability, Ocean-atmosphere interactions, Weather to Climatic modelling and forecasting
Creators: Caminade, Doblas-Reyes, Morse, Ruti
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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As a consequence of the severe drought that occurs from 1970 to 2000, forecasting rainfall over the Sahel at seasonal to decadal time scales became a priority regarding to impacts in terms of food, health and security managements since the 1970’s over this region.
Studies have shown that the actual state of the art General Circulation Model (GCM) forced by observed sea surface temperature (SST) conditions can reproduce the Sahelian rainfall variability at interannual to multi-decadal time scales. However, when a full ocean-atmosphere coupled approach is considered, they mainly fail in reproducing key features of the West African monsoon (WAM), leading to strong uncertainties for simulated future rainfall changes over Africa at the end of the 21st century.
This study highlights the reliability of the European GCM in reproducing key features of the WAM. This is achieved using both seasonal forecasting outputs from the ENSEMBLES project and climate historical simulations performed within the IPCC fourth report assessment. First, deterministic scores are used in order to characterize the different model biases. Then, the simulated teleconnection mechanism between the SST and Sahelian rainfall are highlighted at interannual time scale, and compared with the observed ones. Preliminary results show that most of the coupled models fail in reproducing the oceanic Atlantic cold tongue during summer, leading generally to an overestimation of precipitation over the Gulf of Guinea and significant problems over the Sahel. This bias is partly related to an overestimation of the westerly winds in the Western part of the Atlantic basin. Note also that these “coarse” resolution models do not capture the observed summer rainfall maximum over the West African mountains (Fouta-Djalon, Cameroon mounts).
The major biases highlighted for the seasonal forecast simulations are generally similar to the climate simulations ones, with however clear improvements for the ENSEMBLES model versions with respect to the IPCC ones.
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