Estimation of the direct radiative forcing due to sulfate and soot aerosols

Abstract

The direct radiative forcings due to tropospheric sulfate and fossil fuel soot aerosols are calculated. The change in the atmospheric sulfate since preindustrial time is taken from a recent three-dimensional chemistry transport model calculation. A multistream radiative transfer code and observed atmospheric input data is used. The direct radiative forcing due to sulfate is calculated to -0.32 W/m2. Our results for global and annual mean radiative forcing have been compared with results from other model studies. We have assumed a linear relationship between the concentration of fossil fuel soot and sulfate aerosols. The resulting radiative forcing due to soot particles is 0.16 W/m2. Two types of mixtures of sulfate and soot are further assumed. The calculated single scattering albedo is compared to observations.