Saharan Dust and the African Easterly Jet-African Easterly Wave System: Structure, Location and Energetics

The radiative effects of Saharan mineral dust (SMD) aerosols on the structure, location and energetics of the African easterly jet-African easterly wave (AEJ-AEW) system are examined for July-September 2006. Experiments are conducted with and without SMD using the Weather Research and Forecasting (WRF) model, which is radiatively coupled to an interactive dust model. The SMD-modified heating field shifts the AEJ northward, upward and westward, and enhances its zonal asymmetry. These SMD-induced changes to the AEJ are manifest in the AEWs: the northern and southern tracks of the AEWs shift northward (like the AEJ); and the zonal-scale of the AEWs expands and their westward propagation increases. The SMD also strengthens the energetics of the AEJ-AEW system. The domain and temporally averaged baroclinic energy conversion, which is an order of magnitude larger than the barotropic conversion, increases by a factor of 2.5. The eddy kinetic energy and generation of available potential energy increase by factors of 1.5 and 2.7, respectively. The implications of an SMD-modified AEJ-AEW system for West African precipitation and tropical cyclogenesis in the Eastern Atlantic Ocean are discussed.