A New Multi-Plume Stochastic Eddy-Diffusivity/Mass-Flux Model: A Step Towards Unified Turbulence and Convection Parameterization

We propose an approach to represent in a unified manner different types of convection including dry, non-precipitating, and precipitating moist convection and boundary layer turbulence. This parameterization is based on a multi-plume stochastic Eddy-Diffusivity/Mass-Flux (EDMF) approach. Convection is represented by an ensemble of laterally entraining plumes. Condensation and precipitation within plumes are represented by a simple but realistic cloud microphysics scheme. Lateral entrainment is modeled with a Monte-Carlo approach. This EDMF approach is implemented in a single-column model (SCM) and leads to a realistic representation of variability between convective plumes. We show that it captures the essential features of moist boundary layers ranging from stratocumulus to shallow and precipitating cumulus regimes. A detailed comparison of benchmark cases with large-eddy simulation (LES) results shows the value of the approach. The new approach realistically represents smooth transitions between different convective regimes including dry, shallow and deep convection without any arbitrarily-defined trigger functions. This multi-plume stochastic EDMF model simulates different types of convective plumes (that are associated with different regimes) co-existing within one horizontal domain.