Observational evidence linking precipitation and mesoscale cloud fraction in the southeast Pacific

Abstract

Precipitation has been hypothesized to play an important role in the transition of low clouds from closed to open cell cumulus in regions of large-scale subsidence. A synthesis of A-Train satellite measurements is used to examine the relationship between precipitation and mesoscale cloud fraction across a transition region in the southeastern Pacific. Low cloud pixels are identified in 4 years of CloudSat/CALIPSO observations and along-track mean cloud fraction within 2.5–500 km surrounding the clouds calculated. Results show that cloud fraction decreases more rapidly in areas surrounding precipitating clouds than around nonprecipitating clouds. The closed to open cell transition region appears especially sensitive, with the surrounding mesoscale cloud fraction decreasing 30% faster in the presence of precipitation compared to nonprecipitating clouds. There is also dependence on precipitation rate and cloud liquid water path (LWP), with higher rain rates or lower LWP showing larger decreases in surrounding cloud fraction.