Abstract
In order to provide a framework to elucidate the problem of aerosol mixing from different sources and its chemical and radiative implications, we present a 3D simulation of the redistribution of three atmospheric contaminants during the INDOEX Intensive Field Phase in March 1999: black carbon (BC) as a carbonaceous aerosol marker, sulphur dioxide (SO
2) (a sulphate precursor) and soil dust. In Part 1 of the paper, we focussed on the spatio-temporal redistribution of BC, because: (i) it allowed us to present the methodology; (ii) we could provide a first model validation because a large set of BC measurements is available and, unlike SO
2, it is chemically inert; (iii) BC is an important contributor to aerosol optical depth. In both parts of the paper, we use the CSU RAMS mesoscale model coupled with the GEIA and EDGAR emission databases (for BC and SO
2, respectively), and an online aeolian dust uptake scheme. The area under study ranges from 40°E to 100°E and 5°S to 30°N, and the modelled period is the month of March 1999. Similar to what we demonstrated for BC in Part 1, comparison with available observations suggests that the model results are realistic for dust and SO
2. Mineral dust is found to be a major component of the atmospheric column in the north of the INDOEX area when dust outbreaks occur, but in the south, anthropogenic aerosols (carbonaceous and sulphates) predominate. Finally, we provide an estimate of total optical depth from continental aerosols: BC, dust and sulphate.