African dust source regions for observed dust outbreaks over the Subtropical Eastern North Atlantic region, above 25°N

Abstract

High mineral dust-laden air mass potential source regions affecting the Marine Boundary Layer (MBL) of the Subtropical Eastern North Atlantic Region above 25°N (SENAR), directly or by means of gravitational settlement, were objectively identified. We introduced a new hybrid Lagrangian-Eulerian receptor model, in which air mass residence time probability maps in the geographical domain latitude = [5°N, 60°N], longitude = [70°W, 30°E] were combined with TOMS-AI data (TAPI Index), and with simulated Total Suspended Particles (TSP) with the BSC/DREAM model (SDPI Index). Both approaches show a good agreement. For dust gravitational settlement episodes within the MBL, the dust sources are located in southernmost latitudes compared to those associated with lower air mass transport. A seasonal variability in potential dust sources is found with both approaches, TAPI and SDPI. In winter, most dust sources are located within the Sahara in an area bounded by latitude = [18°N, 35°N], longitude = [15°W, 15°E]. In summer, a high dust-laden air mass reservoir above the Atlantic Ocean has been found during episodes for low altitudes, and dust source regions in the Sahara have been identified for middle and upper altitudes. The Bodelé depression was found to have a minor impact on dust outbreaks affecting the SENAR.