Satellite observations of aerosols and clouds over South China from 2006 to 2015: analysis of changes and possible interactions

Abstract. Aerosol and cloud properties over South China during the 10-year period 2006–2015 are analysed based on observations from passive and active satellite sensors and emission data. The results show a decrease in aerosol optical depth over the study area by about 20 % on average, accompanied by an increase in liquid cloud cover and cloud liquid water path (LWP) by 5 % and 13 %, respectively. Analysis of aerosol types and emissions suggests that the main driver for their reduction is a decrease in biomass burning aerosols. These changes occurred mainly in late autumn and early winter months and coincided with changes in cloud properties. For the latter, possible explanatory mechanisms were examined, including changes in circulation patterns and aerosol-cloud interactions. Further analysis of changes in aerosol vertical profiles demonstrates a consistency of the observed aerosol and cloud changes with the aerosol semi-direct effect, which depends on their relative heights. Based on this mechanism, less absorbing aerosols in the cloud layer would lead to an overall decrease in evaporation of cloud droplets, thus increasing cloud LWP and cover.