Implementation of CLUBB in COAMPS

Various boundary layer (BL) parameterizations have been developed for numerical weather prediction (NWP) models to represent turbulence and cloud processes in the BL. Due to relatively coarse resolutions used by NWP models, cumulus schemes for shallow and/or deep convection are needed to further account for the subgrid variability of BL convection. In this traditional approach, careful consideration is required when adjusting the interaction between the BL and cumulus schemes. A different approach is to use a probability density function (PDF) parameterization, such as the Cloud Layers Unified by Binormals (CLUBB) scheme. CLUBB, which predicts the joint PDFs of subgrid turbulent variations of vertical motion, moisture and temperature, is considered a unified parameterization since a single set of equations is applied to shallow/deep cumulus and stratiform clouds.

In this study the CLUBB parameterization (Larson 2017) is implemented in the Navy’s regional numerical weather prediction model (Coupled Ocean/Atmosphere Mesoscale Prediction System - COAMPS^®). Our current focus is to assess the impact of CLUBB on the marine boundary layer structure. BL cloud simulations for the VAMOS Ocean-Cloud-Atmosphere-Land study will be presented at the conference.