Ensemble-based CMIP5 simulations of West African summer monsoon rainfall: current climate and future changes
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The West African summer monsoon (WASM) rainfall is of significant socioeconomic importance. Therefore, its response to climate change is of great concern to climate scientists. Based on observations, reanalysis, and multi-model ensemble mean (EnsMean) simulations of Coupled Model Intercomparison Project phase 5 (CMIP5) models, the responses of WASM rainfall, as well as some relevant atmospheric features, to global warming are investigated. Results from the historical period (1980–2005) indicate that EnsMean reasonably reproduced the characteristics of WASM rainfall, and the strength and position of the upper-level Tropical Easterly Jet (TEJ) and mid-level African Easterly Jet (AEJ). Under global warming, EnsMean exhibits localized future changes in spatial rainfall pattern; specifically, a statistically significant increase (decrease) is evident over the central-eastern (western) Sahel subregion. Similarly, the annual cycle exhibits a decrease (increase) in pre-monsoon (post-monsoon) rainfall over the region, evident over the Sahel subregion. Increased surface evaporation and enhanced atmospheric moisture convergence are notable over the region of increasing WASM rainfall, while a weakened and possible alteration of large-scale atmospheric circulation features is evident over the study area.
The authors appreciate the World Climate Research Program’s Working Group on Coupled Modeling, which is responsible for CMIP5, and we also thank the climate modeling groups listed in Table 1 for producing and making available their model output. We are also grateful to the services that have operated the GPCP, CRU, and NCEP/NCAR datasets.
This work is supported by the National Nature Science Foundation of China Grant (41675062) and the Research Grants Council of the Hong Kong Special Administrative Region, China (CityU 11305715 and 11335316). The first author is a recipient of a research studentship provided by the City University of Hong Kong (CityU).
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