Climate Impact of Anthropogenic Aerosols in an Interactive Size-Resolving Aerosol-Climate Model

A multi-mode, two-moment aerosol model has been incorporated in the NCAR's CAM3.0 to study the impact of anthropogenic aerosols on the global climate system. Six aerosol modes, namely three sulfate, one external black carbon, one primary organic carbon, and one sulfate/black carbon mixed mode, are included in the model. Atmospheric distributions of these aerosols are predicted undergone transport, mixing, and various aerosol physical and chemical processes including diffusive growth, coagulations, sedimentation, dry and wet deposition, and nucleation as well as impaction scavenging. Aerosol size distributions are then used in the radiation module of CAM to instantly calculate the radiative fluxes under the influence of anthropogenic aerosols. Model results suggest that the major portions of black carbon and sulfate aerosol masses exist as mixed aerosols and therefore the optical properties of this type of aerosols are considered to be most influential to the system. In this study, multiple 60-year long simulations are carried out to examine the impact of the anthropogenic aerosols on the climate system. Strong positive atmospheric forcing and negative surface forcing by the mixed aerosols affect the atmospheric thermal structure and consequently alter values of important parameters including cloud cover, height of planetary boundary layer, surface heat fluxes, and precipitation. The detailed results will be presented and discussed.