The breakup of marine boundary-layer clouds over an inhomogeneous sea surface temperature field

This numerical study examines the breakup of marine atmospheric boundary-layer (MABL) clouds through various physical processes over an inhomogeneous sea surface temperature (SST) field. Three regimes are identified under which the cloud layer will break up. (A) advection of drier air into the MABL for the California case. (B) daytime absorption of solar radiation, occurring most easily over the cold water. (C) mesoscale fluctuations in the flow, producing holes in the cloud layer.The budget study of these three situations concludes that large-scale subsidence, solar radiation, local mesoscale advection, and inhomogeneous surface fluxes cannot be neglected in modeling cloud breakup. This study also confirms the belief that the mixing process alone induced by evaporative entrainment is generally insufficient to predict the breakup of the cloud layer.Sections of this paper are based on an extended abstract by the author and Dr. Steven Stage for the Ninth Symposium on Turbulence and Diffusion held at Riso, Denmark, 1990.