ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-6-4345-2006 Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign Tegen I. 1 Heinold B. 1 Todd M. 2 Helmert J. 1 Washington R. 3 Dubovik O. 4 5 Leibniz Institute for Tropospheric Research, Leipzig, Germany Department of Geography, University College London, UK Oxford University Centre for the Environment, University of Oxford, UK NASA Goddard Space Flight Center, Greenbelt, MD, USA now at: Laboratoire d'Optique Atmosphérique, University of Lille, France 27 09 2006 6 12 4345 4359 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/6/4345/2006/acp-6-4345-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/4345/2006/acp-6-4345-2006.pdf

We present regional model simulations of the dust emission events during the Bodélé Dust Experiment (BoDEx) that was carried out in February and March 2005 in Chad. A box model version of the dust emission model is used to test different input parameters for the emission model, and to compare the dust emissions computed with observed wind speeds to those calculated with wind speeds from the regional model simulation. While field observations indicate that dust production occurs via self-abrasion of saltating diatomite flakes in the Bodélé, the emission model based on the assumption of dust production by saltation and using observed surface wind speeds as input parameters reproduces observed dust optical thicknesses well. Although the peak wind speeds in the regional model underestimate the highest wind speeds occurring on 10–12 March 2005, the spatio-temporal evolution of the dust cloud can be reasonably well reproduced by this model. Dust aerosol interacts with solar and thermal radiation in the regional model; it is responsible for a decrease in maximum daytime temperatures by about 5 K at the beginning the dust storm on 10 March 2005. This direct radiative effect of dust aerosol accounts for about half of the measured temperature decrease compared to conditions on 8 March. Results from a global dust model suggest that the dust from the Bodélé is an important contributor to dust crossing the African Savannah region towards the Gulf of Guinea and the equatorial Atlantic, where it can contribute up to 40% to the dust optical thickness.

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