Large scale reduction in the size of the Tropical Easterly Jet

Analysis of the 41-year (1958-1998) reanalysis wind data from National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) and European Centre for Medium-Range Weather Forecasts (ECMWF) suggest that zonal extent of the Tropical Easterly Jet (TEJ) has reduced between 1960s and 1990s particularly over the Atlantic and African regions. The decrease in NCEP-NCAR reanalysis is more than the decrease in ECMWF reanalysis. The decrease is about 41% and 20% at 100 hPa and 52% and 30% at 200 hPa in NCEP-NCAR reanalysis and ECMWF reanalysis respectively. It is argued that the weakening and disappearing of TEJ over the Atlantic and African regions and prolonged drought conditions over the Sahel region during the past 4-5 decades may be associated with each other.