Séminaire
This work is a model analysis of the desert winds driven by the Sahara heat low (SHL) done by using a two layer Matsuno-Gill model system obtained by coupling a lower Rayleigh frictional layer with an upper almost frictionless layer. We show how this model system can capture the main characteristics of the desert winds and of the African easterly jet. We show the seasonal migration of the Sahara convergence zone on the west flank of the SHL, and how this convergence zone separates the Harmattan winds from the south-westerly flow from the gulf of Guinea. The upwelling generated by Sahara heat low drives the African easterly jet (AEJ). This jet, which projects itself far off the coast of West Africa, is baroclinically unstable and in its northern flank is inertially unstable. In the warm season when the Sahara heat low moves north-westwards, the inflow from the Tropical Atlantic and the AEJ strengthen, while the inflow from the gulf of Guinea weakens. The model input parameters are extracted from NCAR-NCEP Reanalysis data.
cyrille.flamant@latmos.ipsl.fr