IMPACTS OF CLIMATE CHANGE AND REFORESTATION ON DROUGHTS OVER WEST AFRICA USING REGIONAL CLIMATE MODELS

Abstract

Drought is a threat to food security and water availability in West Africa. As part of efforts to improve drought early warning systems, this study investigates the characteristics of West African droughts, evaluates the ability of CORDEX regional climate models to simulate the droughts and examines the impacts of future climate change (2031-2060, under the scenario RCP45) and reforestation on the characteristics of droughts. The Standardized Potential Evapotranspiration Index (SPEI) was used to define drought occurrence. The study applied the Principal Component Analysis (PCA) on Climate Research Unit (CRU) dataset and model simulations to identify spatial patterns in West African droughts. It studied the relationships between the droughts and atmospheric teleconnections. The capability of the models in reproducing the characteristics of West African droughts was investigated. Furthermore, Regional Climate Model (RCM) experiments, using RegCM4 and WRF, were undertaken to investigate the potential impact of reforestation over Savanna (8 N-12 N) on drought over West Africa in near future (2031-2060) under the scenario RCP45. RegCM4 and WRF were forced with HadGEM2-ES and the ECHAM6 respectively. The study evaluated the performance of both regional climate models to simulate the present-day (1971-2000) mean climatology on seasonal basis while the impacts of global warming and reforestation on drought regimes were investigated using Self-Organizing-Map (SOM). The study showed that about 60% of West African droughts can be grouped into 4 patterns (or modes). The first pattern featured drought over east Sahel, the second over west Sahel, the third over Savanna and the fourth over Guinea coast. Most CORDEX models reproduced at least two droughts patterns, but only one model