Direct climate forcing by biomass-burning aerosols: Impact of correlations between controlling variables

摘要: Estimates of the direct climate forcing by condensed organic species resulting from biomass burning have been made using bulk radiative transfer models various complexity and SUNRAY radiation code European Centre for Medium-Range Weather Forecasts general circulation model. Aerosols arising tropical forests savannas as well those fires outside tropics are considered. The give values ranging −1.0 to −0.6 W m−2, which compare with −0.7 m−2 code. There appears be significant uncertainty in these due uncertainties model input parameters. difference is only 13% between obtained taking into account spatial temporal distribution controlling variables global averages all variables. This indicates that effects variations tend compensate. Yet varies up 34% depending on set averages. results show efficiency at biomass-burning aerosols backscatter sunlight cloudy conditions 0.53, a value significantly higher than reported sulfate aerosols. Most relatively low latitude (hence sun zenith angle) aerosol sources relative sources. implication clouds should not assumed reflectivity unity models. Comparison points other potential problems First, use mean optical properties across entire solar spectrum has impact calculated may 23% estimates clear-sky conditions. Second, neglecting multiple scattering introduces differences high angles.