Atmospheric circulation associated with recent Sahelian hydrologic anomalies

Atmospheric circulation over the tropics during recent wet and dry periods over the Sahel has been studied using the NCEP/NCAR re-analysis data set. The results show that the mid and upper level easterly jets play an important role in modulating rainfall variations over the Sahel. In particular, the lower tropospheric easterly jet is stronger during dry years whereas the upper level easterly jet is weaker. Moisture fluxes over West Africa during dry and wetter periods have also been studied, indicating that an important source of moisture for West Africa, is the southern Atlantic. The magnitude of the moisture flux in this region is greater during the wet episodes than during periods of droughts.