Possible causes of the Central Equatorial African long-term drought

TLDR: In this article, the authors examined the atmospheric circulation changes related to sea surface temperature (SST) variations that control the equatorial African rainfall and found that the long-termdrought duringApril,May and June overCEAmay reflect the large-scale response of the atmosphere to tropical SST variations.

Abstract: Previous studies found thatCentral Equatorial Africa (CEA)has experienced a long-termdrying trend over the past twodecades. To further evaluate thisfinding,we investigate possiblemechanisms for this drought by analyzingmultiple sources of observations and reanalysis data.We examine the atmospheric circulation changes related to sea surface temperature (SST) variations that control the equatorial African rainfall.Our results indicate that the long-termdrought duringApril,May and June overCEAmay reflect the large-scale response of the atmosphere to tropical SST variations. Likely the drought results primarily fromSSTvariations over Indo-Pacific associatedwith the enhanced andwestward extended tropical Walker circulation. These are consistentwith theweakened ascent overCentral Africa that is associated with the reduced low-levelmoisture transport. The large-scale atmospheric circulation changes associatedwith aweakerWestAfricanmonsoon also have some contribution.These results reinforce the notion that tropical SSTshave large impacts on rainfall over equatorial Africa andhighlight the need to further distinguish the contributionof SSTs changes (e.g., LaNiña-like pattern and IndianOcean warming)due tonatural variability and anthropogenic forcing to the drought.