Cloud Edges and Aerosol–Cloud Interactions

Adiabatic cloud cores have occupied the central stage of investigating aerosol-cloud interactions and developing parameterizations to represent aerosol-cloud interactions in large scale models. However, it is well known that significant portions of a cloud are near cloud edges where the essential interactions with the surrounding environments including aerosols take place, including cloud base, cloud top, and cloud sides. Thus, unlike most conventional studies, this study focuses on the regions of cloud edges, examining the key cloud microphysical (e.g., effective radius, droplet concentration, liquid water content, and relative dispersion), dynamical properties (e.g., vertical velocity, entrainment, and turbulence), and their mutual relationships. Aircraft measurements from several field campaigns are first analyzed to examine the behavioral dependence on the distance to the cloud core and identify potential underlying physical processes. Modeling studies are then conducted to facilitate physical understanding and parameterization development. Potential physical processes include the role of turbulent entrainment-mixing, concurrent occurrence of droplet condensation and aerosol activation near cloud bases, and concurrent occurrence of droplet evaporation and droplet deactivation near cloud tops and cloud sides.