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
