Modelling soil dust aerosol in the Bodélé depression duringthe BoDEx campaign

[摘要] We present regional model simulations of the dust emission events during theBodélé Dust Experiment (BoDEx) that was carried out in February andMarch 2005 in Chad. A box model version of the dust emission model is usedto test different input parameters for the emission model, and to comparethe dust emissions computed with observed wind speeds to those calculatedwith wind speeds from the regional model simulation. While fieldobservations indicate that dust production occurs via self-abrasion ofsaltating diatomite flakes in the Bodélé, the emission model basedon the assumption of dust production by saltation and using observed surfacewind speeds as input parameters reproduces observed dust optical thicknesseswell. Although the peak wind speeds in the regional model underestimate thehighest wind speeds occurring on 10–12 March 2005, the spatio-temporalevolution of the dust cloud can be reasonably well reproduced by this model.Dust aerosol interacts with solar and thermal radiation in the regionalmodel; it is responsible for a decrease in maximum daytime temperatures byabout 5 K at the beginning the dust storm on 10 March 2005. This directradiative effect of dust aerosol accounts for about half of the measuredtemperature decrease compared to conditions on 8 March. Results from aglobal dust model suggest that the dust from the Bodélé is animportant contributor to dust crossing the African Savannah region towardsthe Gulf of Guinea and the equatorial Atlantic, where it can contribute upto 40% to the dust optical thickness.

[学科分类] 大气科学