Modelling the transport of aerosols during indoex 1999 and comparison with experimental data—1: carbonaceous aerosol distribution

We present a 3D simulation of the redistribution of black carbon (BC), a major particulate contaminant, over the Indian Ocean, during the INDian Ocean Experiment intensive field phase in March 1999. We use the CSU RAMS mesoscale model coupled with the BC GEIA emission source. The area under study ranges from 40°E to 100°E and 5°S to 30°N. The modeled period is 1 month (March). The main model results, i.e., the predicted BC mass concentrations, are compared with the available experimental data. Modelled large-scale BC pollution plumes are in qualitative agreement with satellite imagery, and the model-predicted BC concentrations are generally in quantitative agreement with the aircraft data. At the local scale, the vertical profiles and local measurements also show satisfactory agreement with the model. Vertical profiles exhibit in some instances a layered structure, which may be explained by air masses of contrasting origins. This numerical study is a first step in the development of a mesoscale tool intended to investigate the problem of aerosol mixing.