Weakening and Shiing of the Saharan Heat Low Circulation DuringWet Years of theWest African Monsoon

�e correlation between increasedWest African monsoon rainfall and anomalously low surface pressure over the Sahara is well established in observations and global climatemodels, and has been interpreted as a strengthening of the Saharan Heat Low (SHL) during wet monsoon years.�is study uses two atmospheric reanalysis datasets to examine interannual variability of Sahel rainfall and the shallow Saharan Heat Low circulation, which consists of the near surface SHL and the Saharan High in the lowermid-troposphere. During wet Sahel years, the SHL circulation shi�s poleward, producing a drop in low-level geopotential height and surface pressure over the Sahara. Statistically removing the e�ect of the poleward shi� from the low-level geopotential eliminates signi�cant correlations between this geopotential and Sahel precipitation. As the SHL circulation shi�s poleward, itsmid-tropospheric divergent out�ow decreases, indicating a weakening of its overturning mass �ux. �e poleward shi� and weakening of the SHL circulation duringwet Sahel years is reproduced in an idealized, zonally periodicmodel ofWest Africa; a wide range of imposed sea surface temperature and land surface albedo perturbations in thismodel produce amuch larger range of variations in the SHL that nevertheless have similar quantitative associations with Sahel rainfall as in the reanalyses. �ese results disprove the idea that enhanced Sahel rainfall is caused by strengthening of the SHL overturning. Instead, a stronger SHL circulation inhibits Sahel rainfall, or some other forcing causes both an increase in Sahel rainfall and a weakening of the SHL circulation.