Estimate of Sahelian dust emissions in the intertropical discontinuity region of the West African Monsoon

A three-dimensional mesoscale numerical simulation has been performed to investigate the dust emissions over the Sahel associated with strong near-surface winds in the region of the West African Inter Tropical Discontinuity (ITD) during the summer, when the ITD is located over Niger and Mali around 18 degrees N. The study focuses on the period from 2 to 12 July 2006, in the framework of the African Monsoon Multidisciplinary Analysis (AMMA) Special Observing Period 2al. The comparison with observations suggests that the model can be used reliably to analyze and quantify the dust emissions associated with the strong near-surface winds blowing over the Sahelian dust sources during the period of interest. The daily mean values of dust load related to the strong winds on both side of the ITD, as estimated from the simulation within the model domain (2 degrees W-16 degrees E, 12-28 degrees N), are in excess of 2 Tg on some of the days of the 2-12 July 2006 period. In the present case, the dust load associated with the strong winds south of the ITD accounts for between one third and two thirds of the total load mobilized in the ITD region over the entire domain on a given day. It is simulated to range between 0.5 and 0.8 Tg on average. This study suggests that emissions driven by strong surface winds occurring on both sides of the ITD while lying across the Sahel may contribute significantly to the total dust load over West and North Africa observed annually.