| Abstract: | This paper discusses the vapor-driven convection over snow and its limitations. It is shown on the basis of the moist convective plume model that vapor flux from the evaporating snow surface can drive convection, and maintain a super-cooled water cloud layer, without the assistance of heat flux from the surface, or entrainment or radiative cooling, at cloud top.Since the saturation vapor pressure over water is higher than that over ice, the base of the super-cooled water cloud has a lower limiting height. When the cloud base is lowered to this height, the air at the bottom of the convective layer is just saturated with respect to ice and the evaporation of snow stops, as does the vapor-driven convection. This limiting cloud base height varies with snow-surface temperature. The lower the snow temperature, the higher the cloud base height limit for continued convective transfer from the surface. |
