Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite-based lidar

There have been many proposed processes by which clouds modify aerosol properties, suggesting that aerosol properties near clouds are different than far from clouds. We provide the first satellite-based lidar observations of backscatter and color ratio, quantities directly related to aerosol properties, as a function of distance to cloud edge for boundary layer clouds over the western tropical Atlantic. We show backscatter and color ratio are enhanced adjacent to cloud edge, particularly near cloud top and cloud base. Specifically, layer integrated median backscatter increases by 31 ± 3% and 42 ± 2%, at wavelengths of 532 nm, and 1,064 nm, respectively, and layer averaged color ratio increases by 15 ± 5%. Backscatter calculations suggest our observations adjacent to cloud are best explained by an aerosol size distribution with reduced number concentration, increased median radius, and decreased width compared to far from cloud.