Characterization of West African Jet Streams and Their Association to ENSO Events and Rainfall in ERA-Interim 1979–2011

Abstract EN

The interannual variability of West African jet streams and their association with rainfall are reexamined using European Reanalysis ERA-Interim 1979–2011.

The objective of the study is to characterize their climatology and role in rainfall variability in western Sahel.

Wavelet analysis was used on wind speed data and implications to ENSO were discussed subsequently.

Our results show that while the low-level African Westerly Jet (AWJ) correlates well with rainfall south of the equator in boreal winter months, the Tropical Easterly Jet (TEJ) and African Easterly Jet (AEJ) correlate better with rainfall north of the equator in the boreal summer months.

Results of interannual-to-decadal variability in 200 mb, 600 mb, and 850 mb of zonal wind reveal that there is enhanced variability in the 2–8 year band.

Also, the TEJ, AEJ, and AWJ fluctuations are coupled with variations in southern oscillation.

Further analysis suggests a statistically significant association between TEJ and the El Niño events of the 1980s that led to intense drought in the Sahel region of West Africa.

The 2007 moderate La Niña shows a statistically significant coherence with the 500 mb, 600 mb, and 850 mb jets.

These associations are also phase locked, suggesting that the association may be more than by chance.