Atmospheric Chemistry and Physics Aerosol indirect effect on warm clouds over South-East Atlantic, from co-located MODIS and CALIPSO observations

Abstract. In this study, we provide a comprehensive analy-sis of aerosol interaction with warm boundary layer clouds over the South-East Atlantic. We use aerosol and cloud pa-rameters derived from MODIS observations, together with co-located CALIPSO estimates of the layer altitudes, to de-rive statistical relationships between aerosol concentration and cloud properties. The CALIPSO products are used to dif-ferentiate between cases of mixed cloud-aerosol layers from cases where the aerosol is located well-above the cloud top. This technique allows us to obtain more reliable estimates of the aerosol indirect effect than from simple relationships based on vertically integrated measurements of aerosol and cloud properties. Indeed, it permits us to somewhat distin-guish the effects of aerosol and meteorology on the clouds, although it is not possible to fully ascertain the relative con