Enhanced Low-Level Stratus in the FSU Coupled Ocean–Atmosphere Model

Abstract

An empirical planetary boundary layer cloud parameterization has been developed for The Florida State University coupled ocean?atmosphere model to improve low-level clouds in the model. The scheme diagnoses the clouds by combining the PBL depth, ground wetness, and the relative humidity. Winter and summer simulations between 1987 and 1989 suggest an improvement in the low cloud representation compared to the International Satellite Cloud Climatology Project analysis. When implemented in the model, this parameterization results in positive impacts on shortwave fluxes and low-level circulation, particularly along the west coasts of the North and South American continents. Enhanced mechanical forcing at the ocean surface improves the SST representation in the eastern Pacific Ocean basin. Warm versus cold phase ENSO variability of the east Pacific SSTs are also improved during the seasonal simulations. Furthermore, the near-coast diurnal fluctuation of the low cloud is comparable to observations.