Projected Changes in Mean Annual Rainfall Pattern Over West Africa during the Twenty First Century

Abstract

This study analysed projected changes in mean annual rainfall pattern over West Africa during the early (2010-2035), mid (2040-2065) and late (2070-2095) twenty first century using the Norwegian Earth System Model version 1 (NorESM1-M) at ~1.89° X 2.5° horizontal atmospheric resolution. We evaluated the ability of the model to simulate the observed mean annual rainfall for the baseline (1980-2005), using satellite derived precipitation data from Global Precipitation Climatology Project (GPCP). Projected changes in mean annual rainfall for the twenty first century, were calculated relative to the base line period using three possible future levels of atmospheric greenhouse gases concentration referred to as Representative Concentration Pathways (RCPs) 2.6 Wm-2, 4.5 Wm-2 and 8.5 Wm-2. The result of the analysis shows that, the model generally reproduced the observed mean annual rainfall pattern with maximum and minimum rainfall of ~2600 mm and ~50 mm respectively. The projected changes in mean annual rainfall pattern show that rainfall amount increases over the Guinea coast and decreases inland. Also the mid twenty first century, is projected to experience more changes in rainfall pattern than the early and late twenty first periods, with RCP 4.5 projecting the highest level of change. It is anticipated that if the projected changes in mean annual rainfall pattern occur in the future, it may lead to stress on water dependent sensitive sectors in the region.