The role the Saharan Heat Low plays in dust emission and transport during summertime in North Africa

Abstract

The Saharan Heat Low (SHL) is an important element in the meteorological system in North Africa in summer. However, it is unclear how the SHL affects North African dust emission and transport. Here we investigate the impact of the SHL on dust emission and transport on synoptic time scales in North Africa during the summer over the period 2003–2015 using satellite retrievals of dust optical depth (DOD) and vertical profiles. During the cool phases of the SHL, dust is preferentially emitted from the Bodele depression. Then, as the SHL warms, the dust emitted from the Bodele depression is advected westward due to the intensified African Easterly Jet, resulting in anomalously high DOD values over Mali and Mauritania, where persistent lower troposphere convergence within the SHL sustains the high concentrations of dust. Thus, the persistently high dust DOD from satellite retrievals over Mali and Mauritania in conditions of warm SHL are a combination of dust advection from the east and local emission.