OBSERVATIONS OF MESOSCALE CELLULAR CONVECTION FROM THE MARINE STRATOCUMULUS PHASE OF FIRE

A common mode of convection within the atmospheric boundary layer, mesoscale cellular convection (MCC), assumes the form of an organized array of three-dimensional polygonal cells. This study employs aircraft data, collected off the coast of California during the marine stratocumulus phase of the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE), to investigate the closed cell variety of MCC, Forty-five transects of closed marine mesoscale convective cells are utilized in this study. Data from these transects are used to calculate first-order and scale-dependent second-order kinematic, thermodynamic, and radiation statistics. From these statistics, a conceptual model of closed MCC is constructed detailing the horizontal and vertical structure of the tells in coupled as well as decoupled boundary-layer environments. Mesoscale convective cells not only have a profound influence on the radiation budget of their environment, but also play a key role in governing the exchange of heat, moisture, and momentum between the atmosphere and the surface. During FIRE, the MCC-scale structures were found to be buoyantly-driven above cloud base and driven by perturbation pressure forces below. Microscale eddies generally worked in tandem with these MCC-scale structures to transport heat and moisture vertically throughout the cells. Microscale eddies were responsible for most of this transport within the surface layer, while MCC-scale structures performed most of the transport at mid-levels within the cells.