Impact of shallow convection parameterization on simulations of stratocumulus clouds

During VOCALS-REx , Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) was used to provide real-time forecasts for the field program in the southeast Pacific off Chilean coast. It was found that sporadic grid-scale convection frequently occurred offshore over areas where the convective instability was usually present. Analysis suggested that it was likely due to a lack of shallow convection parameterization in the model. Recently, we implemented University of Washington's shallow convection parameterization in COAMPS. We applied the single column mode of COAMPS to two shallow cumulus convection cases (BOMEX and RICO) following GCSS 1-D setups. In both cases, the parameterization gives reasonable structure for the shallow convective boundary layers. We applied the regional COAMPS to the VOCALS-REx area to further study the impacts of shallow cumulus convection on stratocumulus simulations. Some preliminary simulations show encouraging results. The frequency of grid-scale convection occurrence is reduced because the shallow convection parameterization removes the convective instability. Currently, we are systematically analyzing the results and will present them in the conference.