Maintenance of the African easterly jet

The maintenance of the African easterly jet (AEJ) has been examined using a zonally symmetric general circulation model with simple parametrizations. It is shown that the AEJ is maintained in association with two diabatically forced meridional circulations: one associated with surface fluxes and dry convection in the Saharan heat-low region and one associated with deep moi st convection in the intertropical convergence zone equatorward of this. Th e heat-low heating, which reaches the height of the AEJ around 700 mb, is p articularly important in maintaining the AEJ and its associated meridional gradients in potential vorticity. It is concluded that the mean observed AE J results from a combination of the diabatically forced meridional circulat ions which maintain it and easterly waves which weaken it.