Estimation of shortwave direct radiative forcing of biomass-burning aerosols using new angular models

Using a new angular distribution model (ADM) for smoke aerosols, the instan taneous top-of-atmosphere (TOA) shortwave aerosol radiative forcing (SWARF) is calculated for selected days over biomass-burning regions in South Amer ica. The visible and infrared scanner data are used to detect smoke aerosol s and the Clouds and the Earth's Radiant Energy System (CERES) scanner data from the Tropical Rainfall Measuring Mission are used to obtain the broadb and radiances. First, the ADM for smoke aerosols is calculated over land su rfaces using a discrete-ordinate radiative transfer model. The instantaneou s TOA shortwave (SW) fluxes are estimated using the new smoke ADM and are c ompared with the SW fluxes from the CERES product. The rms error between th e CERES SW fluxes and fluxes using the smoke ADM is 13 W m(-2). The TOA SWA RFs per unit optical thickness for the six surface types range from -29 to -57 W m(-2), showing that smoke aerosols have a distinct cooling effect. Th e new smoke ADM developed as part of this study could be used to estimate r adiative impact of biomass-burning aerosols.