2005: Aerosol and cloud property relationships for summertime stratiform clouds in the northeastern Atlantic from Advanced Very High Resolution Radiometer observations

were used to investigate the feasibility of empirically deriving estimates of the aerosol indirect radiative forcing. A retrieval scheme was used to derive cloud visible optical depth, droplet effective radius, cloud layer altitude, and pixel-scale fractional cloud cover. A two-channel aerosol retrieval scheme was used to determine aerosol optical depth in cloud-free pixels. Mean aerosol optical depths derived from the cloud-free pixels in 1 1 latitude-longitude regions on a given satellite overpass were associated with mean cloud properties derived from the cloudy pixels in the same region for the same satellite overpass. The analysis was restricted to 1 regions that contained only single-layered, low-level cloud systems. Because aerosol and cloud properties are highly variable, results for the 4-month period were composited into 5 5 latitude-longitude regions and averaged to obtain reliable trends in the cloud properties as functions of aerosol burden. Consistent with expectations for the aerosol indirect effect, in some 5 regions, droplet effective radii decreased, and cloud visible optical depths increased as aerosol optical depths increased. The hypothesis that drizzle is suppressed in polluted clouds predicts that liquid water path should increase as aerosol burden increases. In thre