Microphysical Aspects of Representing Cloud Regime Transitions in Regional Forecast Models

Correctly representing cloud regime transitions in marine boundary layers is a challenge for regional forecast models. An accurate mesoscale model forecast depends on robust microphysical and boundary layer parameterizations. This study will evaluate the performance of various microphysical parameterizations in the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) over the southeast Pacific, where stratocumulus sheets frequently persist over periods of several days and transition into open-cell, shallow cumulus convection further west of the coast. Model output will be compared with data collected from the NOAA Research Vessel Ronald H. Brown over the course of the VOCALS–Rex field campaign, as well as with C–130 flights as applicable. Among our goals will be to evaluate a new microphysical parameterization specifically tuned for shallow convection and to scrutinize the performance of COAMPS for deep, stably stratified boundary layers observed from the ship during VOCALS.