Sahelian Precipitation Change Induced by SST Increase: The Contrasting Roles of Regional and Larger-Scale Drivers

Changement des précipitations au Sahel induit par l'augmentation de la TSM : Les rôles contrastés des facteurs régionaux et à plus grande échelle

Dixon, Ross D. ; Peyrillé, Philippe ; Guichard, Françoise

Année de publication
2019
Résumé
<p align=justify>Representing the West African Monsoon is a major challenge in climate modeling because of complex mechanisms of interaction across scales. We study the monsoon precipitation response to a 4K increase in sea surface temperatures using an idealized meridional-vertical (2D) model, which allows separating regional- and larger-scale influences. The 2D simulations reproduce key features of Atmospheric Model Intercomparison Project simulations and indicate that, in response to sea surface temperature increase, large-scale changes induce a decrease of Sahel precipitation, while regional-scale mechanisms generate a southward shift of the rainband. Large-scale changes moisten and warm the free troposphere, while regional circulation changes increase low-level moisture. Precipitation in the control simulations accounts for much of the variance in precipitation change for both Atmospheric Model Intercomparison Project and 2D simulations. This response is strongly connected to the large-scale drivers of temperature and moisture, with an additional spread associated with the formulation of the convective parameterization.</p>
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