First Measurements Based Estimates of Shortwave Aerosol Direct Radiative Effects over Cloudy Sky

Biomass burning smoke can strongly absorb solar radiation, particularly at short wavelengths (0.1 ~ 4.5 um), and their direct and indirect radiative effects over cloudy sky get increasing interests in recent climate change studies. It has been shown that these aerosols have a positive direct radiative effect (DRE) (i.e., radiative warming) when presence above bright cloud. Satellite measurements such as Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) have been used in this study, to examine the aerosol radiative effects over clouds in the South American area during August and September (2006 – 2012), where large amount of smoke from biomass burning activities in amazon forest area have been found to overly persistent boundary layer stratocumulus clouds. Based on the aerosols and clouds properties from both satellite and ground observations, supplement by a four stream radiative transfer model, the direct radiative effects due to aerosols above clouds have been calculated, which can be used to further assess the total direct radiative effects due to aerosols over both clear sky and cloudy sky. Quantitative results will be further provided.