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Subproject 3.8

Regional modelling of Saharan dust export to the Tropical Atlantic

Emission and transport of Saharan dust and primary marine aerosol is computed to examine multi-years of the spatiotemporal distribution of the size-resolved atmospheric dust load and deposition in the Tropical Atlantic. For this, the regional dust model COSMO-MUSCAT is used to simulate the microphysical and chemical aerosol properties that are measured at the Cape Verde Atmospheric Observatory (CVAO).

Emission, transport and deposition of Saharan dust into the tropical North-East Atlantic have been simulated for the entire period 2007 to early 2009. Specific emphasis is on the determination of dust source regions relevant for dust arriving in the Cape Verde region. The specific objectives of the project are (1) advancing the synthesis of regional model results with long-term measurements at the: microphysical, chemical and optical properties at CVAO; (2) establishing relationship of dust transported to the Tropical Atlantic to dust sources in the Sahara for assessing impacts of climate change on dust export; and (3) assessing Saharan dust transport pathways and mixing processes influencing chemical processing of dust particles. In addition, the model results will provide simulated fields of Saharan dust optical thickness and size-resolved dry and wet deposition for studies of physical and biological dust effects in the Tropical Atlantic.

Specific attention is given to the source regions of Saharan dust, which determine their mineralogical composition as well as impact the transport pathways. This will be done using satellite imagery from the Meteosat Second Generation (MSG) dust index retrieval that provides temporally high-resolved qualitative information on dust emission frequencies. This will be the basis for an improved description of dust emissions in particular for mountainous regions.

Fig.1: Dust source activation frequency on a 1°x1° grid for 2006/02-2010/02 (colour shading) inferred from MSG SEVIRI IR dust images at 15 minute native temporal resolution as described by Schepanski et al. (2012). Overlaid vectors show mean wind at 925hPa for 06UCT calculated from ECMWF ERA-Interim reanalysis. Contour lines represent orography.

Schepanski K; Tegen I; Macke A (2012) Comparison of satellite based observations of Saharan dust source areas, Remote Sensing of Environment, 123, pp.90-97. doi: 10.1016/j.rse.2012.03.019

PI: I. Tegen
Contact: I. Tegen (itegen@tropos.de)
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