Direct radiative forcing due to anthropogenic aerosols in East Asia during April 2001

Abstract

An aerosol dynamic model including such processes of nucleation, condensation/evaporation, coagulation, sedimentation, hygroscopic growth and dry and wet deposition coupled with the gas-phase chemistry of the California Institute of Technology model and the aqueous-phase chemistry of the Regional Acid Deposition Model together with meteorological outputs of the MM5 model in a grid of 60 × 60 km2 has been used to estimate anthropogenic aerosols in East Asia (95-145E, 20-50N) for the period of 2-30 April 2001 in the ACE-Asia experimental period. During this period an Asian dust event has been observed from 10 to 13 and 24-26 April in the Korean peninsula. The estimated anthropogenic aerosols excluding the Asian dust are implemented to estimate radiative forcing at the surface, at the top of atmosphere (TOA) and atmospheric aerosol absorption in East Asia using the National Center for Atmospheric Research column radiation model of the community climate model. The results indicate that the area averaged column integrated anthropogenic aerosol concentration in East Asia is estimated to be about 20 mg m-2, of which 46%, 29%, 20%, 4% and 1% are contributed by mixed type, inorganic (IOC), sea salt, organic carbon and black carbon aerosol, respectively. The daytime area mean direct shortwave radiative forcing at the surface is found to be about -5.9 W m-2, of which IOC and the mixed type aerosol contribute about 95% whereas that at TOA is about -4.1 W m-2, of which the IOC and the mixed type aerosol contribute more than 90%. Consequently the area mean atmospheric absorption due to anthropogenic aerosol layer in East Asia is about 1.8 W m-2. The result clearly confirms the existence of a cooling effect (negative forcing) due to the direct effect of anthropogenic aerosols at the surface and TOA in East Asia. However, the atmosphere of the troposphere above the ground is slightly heated due to absorbing aerosol layers that are composed of black carbon and the mixed type aerosol. © 2004 Elsevier Ltd. All rights reserved.