Abstract
This study assessed the performance of 24 simulations, from five regional climate models (RCMs) participating in the Coordinated Regional Climate Downscaling Experiment (CORDEX), in representing spatiotemporal characteristics of precipitation over West Africa, compared to observations. The top five performing RCM simulations were used to assess future precipitation changes over West Africa, under 1.5 °C and 2.0 °C global warming levels (GWLs), following the representative concentration pathway (RCP) 8.5. The performance evaluation and future change assessment were done using a set of seven ‘descriptors’ of West African precipitation namely the simple precipitation intensity index (SDII), the consecutive wet days (CWD), the number of wet days index (R1MM), the number of wet days with moderate and heavy intensity precipitation (R10MM and R30MM, respectively), and annual and June to September daily mean precipitation (ANN and JJAS, respectively). The performance assessment and future change outlook were done for the CORDEX–Africa subdomains of north West Africa (WA-N), south West Africa (WA-S), and a combination of the two subdomains. While the performance of RCM runs was descriptor- and subregion- specific, five model runs emerged as top performers in representing precipitation characteristics over both WA-N and WA-S. The five model runs are CCLM4 forced by ICHEC-EC-EARTH (r12i1p1), RCA4 forced by CCCma-CanESM2 (r1i1p1), RACMO22T forced by MOHC-HadGEM2-ES (r1i1p1), and the ensemble means of simulations made by CCLM4 and RACMO22T. All precipitation descriptors recorded a reduction under the two warming levels, except the SDII which recorded an increase. Unlike the WA-N that showed less frequency and more intense precipitation, the WA-S showed increased frequency and intensity. Given the potential impact that these projected changes may have on West Africa’s socioeconomic activities, adjustments in investment may be required to take advantage of (and enhance system resilience against damage that may result from) the potential changes in precipitation.
Highlights
West Africa’s climate is influenced by several factors including altitude, proximity to the tropicalAtlantic Ocean, migration of the Inter-Tropical Convergence Zone (ITCZ), and the location of dominant atmospheric high- and low-pressure systems [1]
For the WA-S region (Table 4), CCLM4 forced by Max Planck Institute (MPI)-M-MPI-ESM-LR (r1i1p1) and ICHEC-EC-EARTH (r12i1p1), RACMO22T forced by MOHC-HadGEM2-ES (r1i1p1), HIRHAM5 forced by ICHEC-EC-EARTH (r3i1p1), and an ensemble mean for simulations produced by RACMO22T
The five model runs were CCLM4 forced by ICHEC-EC-EARTH (r12i1p1), RCA4 forced by CCCma-CanESM2 (r1i1p1), RACMO22T forced by MOHC-HadGEM2-ES (r1i1p1), and the ensemble means of simulations done by CCLM4 and RACMO22T
Summary
Atlantic Ocean, migration of the Inter-Tropical Convergence Zone (ITCZ), and the location of dominant atmospheric high- and low-pressure systems [1]. The region’s main rainy season occurs between. April and September in coincidence with the northerly migration of the Inter-Tropical Convergence Zone (ITCZ). Countries like Ghana and Côte d’Ivoire experience bi-modal rainfall with the main (minor) rainy season being April to July (September to October). In between these rainy seasons are dry periods, mainly from November to March. Temperatures across the region are relatively high throughout the year ranging from around 21 to 30 ◦ C. The highest temperatures are experienced in the Sahara Desert, north of the region, where average maximum temperatures regularly exceed 40 ◦ C
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