Group seminar on 3. November, 14:15 CET

Seasonal Cycle of Precipitation in Equatorial West Africa and Atmospheric Circulation Structures

A well known explanation for the seasonal precipitation cycle over West Africa is the seasonal excursion of the ITCZ. A look in historical literature shows that its use has long been controversial, with some scientist strongly criticizing its applicability over Africa. Regardless, the ITCZ concept remains the common explanation for rainfall seasons in equatorial west Africa. Motivated by recent studies on the ITCZ over central Africa which show that the precipitation maximum is not always connected to low level convergence.

This study tries to understand if a similar phenomenon can also be found further west. The study is based on analysis of TRMM and ERA-5 datasets in an area between 20W -20°E and 20S -20N. The analysis reveals that in the west, the maximum of precipitation is connected to low level convergence in contrast to the east. Moreover, in the west and less so in the east the maximum of precipitation is bordered in the north by a strong convergence zone due to the north-easterly flow of the Harmattan and the south-westerly flow of the west African moonson.