Abstract
Abstract. We present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three typical months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bodélé Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bodélé dust transported towards the Cape Verde Islands is evident in winter when the Bodélé source area is most active and dominant with regard to activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted.
Highlights
The Sahara as the World’s most important dust source adjoins directly to the Atlantic ocean (e.g. Prospero et al, 2002; Middleton and Goudie, 2001; Goudie and Middleton, 2001; Washington et al, 2003)
The Sahara and Sahel region over North Africa contains several potential dust source areas, mostly located in the foothills of the mountain areas where endorheic drainage systems, and wadis opening to fluvial fans provide a large amount of sediment available for aeolian erosion (e.g. Washington et al, 2003; Schepanski et al, 2007)
Patterns of the model simulation agree in general with the remotely sensed patterns, but they disagree in detail: The maximum mean aerosol optical thickness (AOT) values simulated over the Bodele Depression is around 2.8, measurement retrievals indicate AOTs up to 5 by the DeepBlue product
Summary
The Sahara as the World’s most important dust source adjoins directly to the Atlantic ocean (e.g. Prospero et al, 2002; Middleton and Goudie, 2001; Goudie and Middleton, 2001; Washington et al, 2003). A major part of the Saharan mineral dust is exported towards the northern tropical Atlantic Kaufman et al, 2005) Based on such analyses of satellite retrievals, the Bodele Depression was claimed to be the major source for dust transport to the Amazon (Koren et al, 2006). The relation of AOT of dust (in the following referred to as AOT) and atmospheric dust column load and deposition fluxes is discussed. This addresses the question whether it is possible to determine dust deposition from AOTs retrievals based on space-borne measurements provided by e.g. MODIS or SeaWiFS
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