Aerosol-cloud interactions in small cumuli can have a strong two-way component. Although the aerosols can affect cloud and precipitation processes and characteristics, small cumuli can alter the aerosol properties of their immediate environment through cloud and precipitation processes. To study this processing we used observations in and near precipitating and non-precipitating cumulus clouds observed during the Barbados Aerosol Cloud Experiment (BACEX) that was carried out from 15 March to 15 April 2010. The principal observing platform for the experiment was the CIRPAS Twin Otter that was equipped with aerosol, cloud, and precipitation probes and standard meteorological instrumentation for observing the mean and turbulent thermodynamic and wind structure. A Doppler 94 GHz cloud radar was mounted on the top of the aircraft fuselage in an upward facing mode and provided high temporal and spatial characterizations of the cloud and precipitation structures above the aircraft.

The vertical and horizontal distributions of aerosols observed on the 15 flights show a wide range of aerosol conditions that include the most intense African dust event (March 31-April 2) observed at Barbados during all of 2010. In the extreme African dust no clouds were observed and new particle production associated with very clean air was suppressed. But for the weaker African dust events and cases where the accumulation mode aerosol content above the boundary layer is very low, areas of very clean air and new particle production were observed in the vicinity of cumulus clouds. In this study the cloud conditions and processes associated with regions of clean air and new particle production are explored. These processes include wash out by precipitation and CCN depletion in the cloud shell that can subsequently impact new convective elements directly. The role of detrainment and entrainment mixing and evaporation processes on aerosol distributions at the cloud boundaries will be considered for clouds in different phases of their life cycle.