Cloud‐base fluxes in the cumulus‐capped boundary layer

A closure for the fluxes of mass, heat, and moisture at cloud base in the cumulus‐capped boundary layer is developed. The cloud‐base mass flux is obtained from a simplifed turbulence kinetic energy (TKE) budget for the sub‐cloud layer, in which cumulus convection is assumed to be associated with a transport of TKE from the sub‐cloud layer to the cloud layer. The heat and moisture fluxes are obtained from a jump model based on the virtual‐potential‐temperature equation. A key part of this parametrization is the parametrization of the virtual‐temperature flux at the top of the transition zone between the sub‐cloud and cloud layers. It is argued that pressure fluctuations must be responsible for the transport of TKE from the cloud layer to the sub‐cloud layer.