Dynamics of Shallow Cumulus Clouds in the Presence of Black Carbon Aerosol

The impacts of light-absorbing smoke aerosols on the dynamics of liquid-phase cumulus clouds over the Amazon is revisited in light of new observations from the tropical Indian Ocean suggesting that cumulus buoyancy is enhanced under conditions of greater concentrations of black carbon aerosols. An observational basis for the expected “burn-of” of clouds, known as the semi-direct effect, has greater support in the literature for Amazon clouds compared to Indian Ocean clouds. Thus, an integrated analysis of satellite and surface observations for both locations seeks to identify the similarities and differences between clouds and aerosols in these two locations to determine why there is a clear signal of smoke reducing clouds over the Amazon, but not over the Indian Ocean. Key differences between the regions may be as simple as differences in the relative vertical distributions of aerosol and cloud, or related to more complex aspects of the surface energy balance and boundary layer dynamics. These are explored using a variety of measurements including DOE and NSF surface station data sets, NASA A-Train satellite observations, and NOAA geostationary satellite data.