Cloud Resolving Experiments with a Simplified Higher-Order Turbulence Closure

Description

While CRMs (i.e. model with horizontal grid sizes of ~1-5 km) can permit deep convective circulations to be explicitly represented, boundary layer clouds and shallow convection are still sub-grid scale features that need to be parameterized. In addition, turbulence associated with deep convection must also still be parameterized. Unfortunately, most cloud resolving models (CRMs) use subgrid-scale (SGS) parameterizations that were originally designed for large eddy simulations (LES) and are not applicable for models at the kilometer scale. This poster presents experiments where a CRM is coupled with a computationally efficient SGS turbulence and cloud parameterization. The parameterization is known as Simplified Higher-Order Closure (SHOC) and is a diagnostic higher-order turbulence closure centered around an assumed double-Gaussian probability density function. Previous studies have shown SHOC to be insensitive to the choice of grid spacing selected for boundary layer clouds. Here CRM results are presented for TWP-ICE field campaign to see how SHOC, coupled with the System for Atmospheric Modeling (SAM) CRM, simulates deep convection for various horizontal grid sizes. In addition, results are presented for the super-parameterized Community Atmosphere Model (SP-CAM), which is a unique GCM that uses an embedded CRM in each GCM grid column to replace traditional cloud parameterizations. Here we focus on SP-CAM-SHOC’s simulation of aerosol indirect effects and intra-annual seasonal tropical variability.