Toward a unified parameterization of the boundary layer and moist convection. Part III: Simulations of clear and cloudy convection

A model that employs a new form of mass-flux closure (described in Part I o f this paper) is applied to a variety of clear and cloudy planetary boundar y layers (PBLs) including dry convection from the Wangara Experiment, trade wind cumulus from the Barbados Oceanographic and Meteorological Experiment (BOMEX), and marine stratocumulus from the Atlantic Stratocumulus Experime nt (ASTEX). For Wangara, the simulated variances and fluxes match that expe cted from similarity arguments, while the mean state is a little less mixed than the observations. In the BOMEX simulation, the shape and magnitude of the fluxes and the turbulence kinetic energy budget agree with LES results and observations. However, the liquid water mixing ratio is too large. Thi s is attributed to an underprediction of the skewness. In agreement with ob servations from the ASTEX experiment, many of the model-simulated fields di stinctly reflect a regime in transition between the trade wind cumulus and the classic stratocumulus-topped boundary layers. In general, the simulated entrainment rate tends to be a little underpredic ted in regimes where there is little cloud-top radiative cooling (Wangara a nd BOMEX), while it is overpredicted in regimes where this process is more critical (e.g., ASTEX). Prior work suggests that this may be related to the manner in which the pressure terms are parameterized in the model. Overall , the model is able to capture some key physical features of these PBL regi mes, and appears to have the potential to represent both cloud and boundary layer processes. Thus, this approach is a first step toward unifying these processes in large-scale models.