Local vs. remote controls on forced Sahelian rainfall

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Monday, 5 January 2015
Spencer A. Hill, Princeton University, Princeton, NJ; and Y. Ming

Handout (1.2 MB)

Some models dry the African Sahel in response to uniform SST warming; others wetten it. Myriad local and remote processes determine this behavior, their relative importance and interactions uncertain. We present a conceptual framework for Sahelian rainfall centered on the region's moist stability, in which local processes dictate near-surface moist static energy (MSE) and remote convection controls MSE aloft via the weak temperature gradient dynamical constraint. A remote region's influence on local rainfall depends on that region's (1) convection characteristics relative to Sahelian convection and (2) proximity to the Sahel. We present tests of this picture from a series of atmospheric general circulation model simulations, discuss its limitations, and speculate on its applicability to other regions.