This study investigates the impact of increased global warming on heat stress changes and the potential number of people exposed to heat risks over Africa. For this purpose a heat index has been computed based on an ensemble-mean of high-resolution regional climate model simulations from the Coordinated Output for Regional Evaluations (CORE) embedded in the COordinated Regional Climate Downscaling EXperiment (CORDEX), under two Representative Concentration Pathways (RCPs) scenarios (RCP2.6 and RCP8.5), combined with projections of population growth developed based on the Shared Socioeconomic Pathways (SSPs) scenarios (SSP1 and SSP3). Results show that by the late 21st century, the increased global warming is expected to induce a 12-fold increase in the area extent affected by heat stress of high-risk level. This would result in an increase of about 10-30% in the number of days with high-risk heat conditions, as well as about 6-20% in their magnitude throughout the seasonal cycle over West, Central and North-East Africa. Therefore, and because of the lack of adaptation and mitigation policies, the exacerbation of ambient heat conditions could contribute to the exposure of about 2-10 million person-events to heat stress of high-risk level over Burkina Faso, Ghana, Niger, and Nigeria. Furthermore, it was found that the interaction effect between the climate change and population growth seems to be the most dominant in explaining the total changes in exposure due to moderate and high heat-related risks over all subregions of the African continent.

The Tropical Rainfall Measuring Mission (TRMM) daily (3B42) and monthly (3B43) rainfall products are evaluated relative to synoptic weather station observations in Cameroon and according to the main agro-climatic regions. In order to achieve this goal, deterministic and categorical metrics were used, as well as inter annual variability and seasonnal distributions. Outcomes of the comparison showed that synoptic weather station data are strongly correlated with the TRMM 3B43 data and that rainfall distribution is characteristic for each agro-climatic region. The highest skill scores were observed in the Sudano-sahelian, High Savannah, and Western Highlands zones, while the Uni-modal Equatorial zone displayed the lowest correspondence scores between TRMM rainfall estimates and station-based observations. Daily TRMM 3B42 showed good performance in detecting rainy events, especially for light and moderate intensity rainfall events. TRMM 3B42 overestimates rainfall intensities except in the uni-modal region where rainfall intensities are underestimated. Rainfall seasonnality, as well convective zone are well reproduced by the TRMM datasets. Overall, the skill of TRMM 3B42 decreases for increasing precipitation intensities.

The study aims to assess the local response of the regional climate model version 4.6 (RegCM4.6) to the coupling of ocean-atmosphere interaction in Central Africa. The ability of the model is evaluated over six years (first January 2001, to thirty-first December 2006) by conducting two different experiments with the Grell convective scheme. The experiments are carried out monthly with a spatial resolution of 40 km. The model was forced by ERA-Interim reanalyses and validated by GPCP (Global Precipitation Climatology Project) observational data, ERA 5 and ERA-Interim reanalyses. To evaluate the influence of the slab-ocean, we carried out two different experiments: The first experiment is designed to produce the climatology and force the surface limits of RegCM with the sea surface temperature. The second experiment is designed to couple RegCM with the slab-ocean, which provides mutual interaction between the ocean and the atmosphere. Using statistical tools, we evaluated the model’s ability to simulate precipitation, surface temperature and wind. Both experiments reasonably reproduce the main characteristics of the rainfall regime, temperature and wind. A comparative analysis of the different experiments reveals that the performances of the experiments are similar in Central Africa and in the different homogeneous sub-regions as far as rainfall is concerned, but there are subtle differences. Slab-ocean improvement varies from season to season and from the sub-region to sub-region. However, we note a significant improvement in temperature and rainfall over the Indian Ocean.