African Easterly Waves (AEWs) are the dominant mode of atmospheric variability over West Africa on synoptic scales in the summer. These waves are baroclinic westward propagating disturbances observed in the dynamical fields and convection, with a wavelength of about 3000 km and a period of 3-5 days. They are intermittent on intra-seasonal timescales, and in different studies they have been associated with the modulation and spatial organization of convection in West Africa during the monsoon season. They are also studied as the precursors of tropical cyclones in the Atlantic.

This presentation will focus on the question of the origin and intra-seasonal intermittency of AEWs, investigated through a combination of idealized modeling and analysis of observations. Factors such as the relationship of the waves with the background environment — in particular the African Easterly Jet (AEJ), with convection, and with potential extra-tropical forcing will be examined and discussed.