Les avancées d'AMMA sur les interactions océan-atmosphère

The results gathered since the AMMA/EGEE campaigns of 2005-2007 in the field of air-sea interactions are presented. They show the key role of the Atlantic cold tongue (ACT) in the eastern equatorial Atlantic on the West African monsoon. The strengthening of south easterlies, associated with the Saint-Helena anticyclone, promotes the preconditioning of the thermocline along the equator and the development of the ACT.The equatorial front on its northern boundary, modifies the surface heat fluxes that affect the circulation in the lower atmosphere. This circulation helps to push moisture northward, toward the West African sub-continent, and impacts the monsoon jump.