Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign I. Tegen1, B. Heinold1, M. Todd2, J. Helmert1, R. Washington3, and O. Dubovik4,* 1Leibniz Institute for Tropospheric Research, Leipzig, Germany 2Department of Geography, University College London, UK 3Oxford University Centre for the Environment, University of Oxford, UK 4NASA Goddard Space Flight Center, Greenbelt, MD, USA *now at: Laboratoire d'Optique Atmosphérique, University of Lille, France
Abstract. 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.
Citation: Tegen, I., Heinold, B., Todd, M., Helmert, J., Washington, R., and Dubovik, O.: Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign, Atmos. Chem. Phys., 6, 4345-4359, doi:10.5194/acp-6-4345-2006, 2006.