Variability and trends of atmospheric moisture in recent West African monsoon season and the Coordinated Regional Downscaling Experiment-Africa projected 21st century scenarios

摘要

The interannual variability and trends of atmospheric moisture flux convergence (MFC) and the flux transport and their roles in wet season rainfall variability during the West Africa monsoon season have been investigated using the Climate Research Unit observational datasets and the National Center for Environmental Prediction reanalysis 2 from 1979 to 2016 and the Coordinated Regional Downscaling Experiment (CORDEX)-Africa model outputs. Particular emphasis has been placed on the three rainfall zones: the Western Sudano Sahel, the Eastern Sudano Sahel and the Guinea Coast. The MFC shows largest variability and impact on rainfall in the Western Sudano Sahel, followed by the Guinea Coast, but there is no significant impact in the Eastern Sudano Sahel. Furthermore, the MFC shows significant positive trends at the Sahelian locations but not at the Guinea Coast. The CORDEX-Africa models adequately simulate the climatology and spatial patterns of the mean June to September atmospheric moisture; however, differences exist in the magnitude and signs of the temporal trend. The model ensemble mean is presented, which better represents the atmospheric moisture during the monsoon rainfall variability. A mean bias-corrected projection of the atmospheric moisture shows enhanced rainfall variability of the Guinea Coast in the representative concentration pathway (RCP) 4.5 and RCP 8.5 at the end of the 21st century.