Factors influencing the mesoscale variations in marine stratocumulus albedo

Measurements of both horizontal gradients and vertical profiles of aerosols, cloud droplets and thermodynamic parameters in the cloud topped marine boundary layer off of central California are presented. They suggest that, while aerosols can indeed modulate cloud albedo, other parameters such as sea surface temperature may similarly affect cloud albedo. Additionally, the impact of aerosols, through sedimentation and precipitation, on cloud optical depths and thus albedo is not always in accord with conventional expectations and can either enhance or decrease the albedo, depending on ambient conditions. Taken together, these results suggest that current estimates of indirect forcing by aerosols could be significantly in error.