Global analysis of aerosol properties above clouds

The seasonal and spatial variability of Aerosol Above Cloud (AAC) properties are derived from passive satellite data for the year 2008. A significant amount of aerosols are transported above liquid water clouds on the global scale. For particles in the fine mode (i.e., radius smaller than 0.3 mu m), including both clear-sky and AAC, retrievals increase the global mean aerosol optical thickness by 25(6)%. The two main regions of originated anthropogenic AAC are the tropical Southeast Atlantic, for biomass-burning aerosols, and the North Pacific, mainly for pollutants. Man-made AAC are also detected over the Arctic during the spring. Mineral dust particles are detected above clouds within the so-called dust belt region (5-40 degrees N). AAC may cause a warming effect and bias the retrieval of the cloud properties. This study will then help to better quantify the impacts of aerosols on clouds and climate.