INFLUENCE OF SEA SURFACE TEMPERATURE AND OUTGOING LONG WAVE RADIATION ON WEST AFRICAN SUMMER MONSOON

Abstract

Rainfall in the tropics is closely linked with other environmental attributes. The influence of Sea Surface Temperature (SST) and terrestrial radiation on West African Summer Monsoon was investigated in this study. This was done by examining the variability of atmospheric circulation features, sea surface temperature and outgoing longwave radiation during West African Summer Monsoon. The interactions between these features and West African Summer Monsoon were also determined. Principal component analysis was also used to find the percentage contribution of forcings on West African Summer Monsoon. The Era Interim reanalysis data were sourced from European Centre for Medium-Range Weather Forecast (ECMWF) with a resolution of 0.1250* 0.1250 from 1998-2012 for 10m U-wind at various pressure levels, Total Precipitation and Sea Surface Temperature. Outgoing Longwave Radiation (OLR) was obtained from Climate Diagnostic Centre for the same period. Extraction and analysis of data were carried out using ferret and Microsoft excel. The study shows a strong positive correlation between Rainfall and SST which increases from the Guinea up to the North and a strong negative relationship between Rainfall and OLR. The wind profile also indicated the presence of moisture throughout the monsoon period. The African Easterly Jet and the Tropical Easterly Jet shown are precipitation or rainfall producing mechanism and represent, among others, major factors or features that influence rainfall, beside Sea Surface Temperature (SST) and Outgoing Longwave Radiation (OLR). The first two principal components for April to October explain 74.2% of the total variance.