Marine boundary layer clouds are of great importance for the heat balance of the earth-atmosphere system. The ocean surface has a very low albedo whereas stratus clouds reflect solar radiation efficiently. The temperature of the ocean surface and the cloud top are simular, which implies that they radiate about equal amounts in the long-wave spectrum. The total radiative forcing of MBL clouds is thus negative.
Basic questions of the mechanisms by which marine clouds are produced, maintained, and dissipated are not yet fully answered. Large field studies, such as FIRE and ASTEX, have given some insight into processes controlling the cloud topped MBL, but have also illustrated the complexity of the MBL clouds.
In this work we have used a numerical model to investigate the sensitivity of the MBL clouds to different parameters controlling the cloud. We have looked at "outer" forces as large scale subsidence and SST as well as the microphysical forcing i.e. CCN spectra, the importance of drizzle formation, turbulence-cloud microphysics and turbulence-radiation interactions.
The model used in the study is an ensemble-average model with a higher order turbulence scheme. The model is run with either a bulk-liquid water formulation or an explicit microphysics formulation. It also includes detailed radiation scheme and a model for the heat fluxes from the ocean