Abstract
This study concerns the West African Sahel. The Sahelian climate is characterized by a long dry season and a rainy season which starts in June and ends in September–October. This latter season is associated with the process of oceanic moisture transfer to the mainland (the West African Monsoon). This movement is governed by an overall moving of the meteorological equator and its low-pressure corridor (Intertropical Convergence Zone, ITCZ) towards the north, under the effect of the attraction of the Saharan thermal depressions and a greater vigor of the anticyclonic nuclei. This study was conducted on 27 Sahelian climatic stations in three countries (Burkina Faso, Mauritania, and Senegal). The method used to determine the modes of this variability and the trends of rainfall is the chronological graphic method of information processing (MGCTI) of the “Bertin Matrix” and continuous wavelets transform (CWT). Results show a rain resumption observed in the recent years over the Sahelian region and a convincing link with the surface temperature of the Atlantic Ocean.
Highlights
If, on a global scale, the rise in temperatures is a certainty, the evolution of global rainfall is much more contrasting, as it is subject to a strong spatiotemporal variability [1].Increased power of evaporation will lead to a greater availability of water vapors
The analysis of rainfall trend evolution shows that, following a long Sahelian drought, rains returned to this part of West Africa
The observations made in the entire Sahel region point to a major change that occurred in the mid-1990s [54,55], which made some scientists use the term “ecologization” [56,57]
Summary
On a global scale, the rise in temperatures is a certainty, the evolution of global rainfall is much more contrasting, as it is subject to a strong spatiotemporal variability [1].Increased power of evaporation will lead to a greater availability of water vapors. Using a climate simulation model, it was proved that a 22% rise in air humidity may be brought towards continents by maritime flows [3]. The results of various studies regarding rainfall evolution show that climate changes have entailed an intensification of precipitation and a repetition of extreme events [4,5,6,7,8]. Given this climate change, a likely increase in extreme events, floods, is to be expected
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