Turbulent Entrainment-mixing and Its Effects on Continental Stratus/stratocumulus Cloud Microphysics Observed During the RACORO Campaign

Marine boundary layer clouds such as stratus and stratocumulus clouds are known to exert significant impact on earth's radiation budget due to its extensiveness and longevity. Unlike their simplistic appearance, however, their microphysics, dynamics and radiative properties are found to be complexly interrelated. Especially entrainment of very dry air above cloud top and how this air mixes with cloudy air significantly modulates cloud microphysics and dynamics. In a recent study on marine stratocumulus clouds, we showed that relevant scale parameters (transition length and scale number) indicated inhomogeneous mixing while observed microphysical relationships indicated homogeneous mixing due to modulation of cloud microphysics during vertical circulation of mixed parcels. Here we make similar investigation on continental stratus/stratocumulus clouds observed in Oklahoma during the Routine AAF CLOUD Optical Radiative Observations (RACORO) campaign. The thermodynamic and aerosol conditions for these clouds were obviously different from those for the marine stratocumulus clouds we investigated in our recent study. The estimated turbulence dissipation rates were different, too. Resultantly the scale number were found to be smaller and microphysical relationships indicated dominant homogeneous mixing signature for the RACORO clouds. More detail will be presented at the symposium.