Atmospheric circulations associated with extreme events in seasonal rainfall over west Africa

Abstract

This study examined the atmospheric circulation pattern associated with extreme rainfall events over West Africa during rainfall season. The atmospheric circulation patterns are crucial in determination of the mechanisms that lead to extreme events in seasonal rainfall. The study specifically, examined the spatial and temporal patterns of rainfall over West Africa; identified the extreme wet and dry years; identified the flow pattern associated with the wet and dry years; and examined the relationship between rainfall and circulation parameters. The two data sets used in this study were rainfall and wind data. The rainfall data set is the global monthly precipitation data set from the Climate Research Unit at the University of East Anglia; while the wind data set is the reanalysis monthly wind data from the National Center for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). The methods of analysis used in this study included, plotting the spatial mean pattern of rainfall; time series analysis of the rainfall over the region of study which included determination of wet and dry years, trend analysis, spectral analysis and correlation analysis of rainfall and wind derived parameters (wind shear and velocity potential over the Indonesia Region); and plotting of winds and the derivatives (diverge~~ and-vorticity) of both regional and global during wet and dry years.