A GLOBAL 3-DIMENSIONAL MODEL STUDY OF CARBONACEOUS AEROSOLS

We have developed detailed emission inventories for the amount of both black and organic carbon particles from biomass burning sources (wood fuel, charcoal. burning, dung, charcoal production, agricultural, sav anna and forest fires). We have also estimated an inventory for organi c carbon particles from fossil fuel burning and urban activities from an existing inventory for fossil fuel sources of black carbon, We also provide an estimate for the natural source of organic matter. These e missions have been used together with our global aerosol model to stud y the global distribution of carbonaceous aerosols. The accuracy of th e inventories and the model formulation has been tested by comparing t he model simulations of carbonaceous aerosols in the atmosphere and in precipitation with observations reported in the literature. For most locations and seasons, the predicted concentrations are in reasonable agreement with the observations, although the model underpredicts blac k carbon concentrations in polar regions. The predicted concentrations in remote areas are extremely sensitive to both the rate of removal b y wet deposition and the height of injection of the aerosols. Finally, a global map of the aerosol single scattering albedo was developed fr om the simulated carbonaceous particle distribution and a previously d eveloped model for aerosol sulfates. The computed aerosol single scatt ering albedos compare well with observations, suggesting that most of the important aerosol species have been included in the model. For mos t locations and seasons, the single scattering albedo is larger than 0 .85, indicating that these aerosols, in general, lead to a net cooling .