Intensification of the Saharan Heat Low: Observations, Attribution, and Implications for Sahel Rainfall

Reanalyses are examined to show that surface temperatures over the Sahara Desert are increasing at a rate that is 3.5 times that of the global mean between 1980 and 2012 and, as a result, the Sahara heat low is strengthening. An analysis of the surface heat balance indicates that this amplified desert warming signal is attributable to increasing atmospheric CO2 concentrations. Most of the surface heating is related to the water vapor/temperature feedback that is triggered on global space scales by the CO2 increases, accompanied by a local disabling of latent cooling at the surface over the desert.

A similar response is seen in well-validated regional model simulations of the mid- and late- 20th century forced by atmospheric greenhouse gas increases according to the representative concentration pathway 8.5 emissions scenario. In response to increases in temperature and geopotential height gradients to the south of the intensified Saharan high, summer rainfall rates and intense events increase over most of the Sahel in the simulations. Evidence for a projected increase in Sahel precipitation is evaluated using observed rainfall.