Mesoscale Cellular Convection

摘要

The large areal extent of mesoscale cellular patterns is cumuli suggests there exists a scale of mesoscale convection that is significant to air-sea exchange mechanisms. The purpose here is to bring together a representative sample of satellite and associated meteorological data concerning these cells, and to propose a hypothesis for them that is based on the extant work on Benard convection. As in the laboratory two classes of cells appear to exist: those with ascent in the cell centers and those with descent in the cell centers. Experiment and theory indicate this may be due to the vertical variation of eddy viscosity. It is suggested that the destabilizing effect of surface heating and cloud top cooling by radiation determine this vertical variation, and that these usually are of greater magnitude than evaporation cooling or release of latent heat. Shear and non- steady-state heating are unfavorable for these mesoscale cells, but rotation probably has no effect. Suggestions for future work are to construct a theoretical model that incorporates anisotropic, variable, eddy exchanges and diabatic energy sources other than latent instability. Suggested experimental work should be carried out in the atmosphere, not in the laboratory, and it should include measurements of eddy flux of heat and momentum as well as the diabatic energy sources. (Author)