A New Stochastic Multiple-Plume Eddy-Diffusivity/Mass-Flux model: A Step Towards a Unified Parameterization

Abstract:

A new mixing parameterization for climate and weather prediction models is developed. The new parameterization represents boundary layer mixing, and non-precipitating and precipitating convection processes in a unified and physically consistent manner. The parameterization builds on a previously tested stochastic multiple-plume eddy-diffusivity/mass-flux (EDMF) approach. The new parameterization includes a realistic model for microphysical processes as part of the mass-flux parameterization, and a parameterization for convective downdrafts. A method to solve the mass-flux dynamics and microphysics simultaneously is developed. This method avoids the need for an iterative solution of the equations and is numerically stable. The new EDMF parameterization is implemented in a single-column model (SCM) and we show that the model is able to capture essential features of moist boundary layers, ranging from the stratocumulus, shallow and precipitating cumulus regimes. Detailed comparisons of a few important cases with LES results are shown to confirm the robustness of the present approach. This new parameterization provides an important step towards a fully unified parameterization of boundary layer, shallow and deep convection.