PNNL

Abstract

The cumulus parameterization framework is called the Cumulus Potential (CuP) scheme. Within this framework, the scheme uses Joint Probability Density Functions (JPDFs) of temperature and moisture and the mean temperature profile to predict the amount and size distribution of fair-weather cumuli. This scheme considers the diversity of air parcels over a heterogeneous surface, and recognizes that some rising parcels become cumuli, while other parcels remain clear updrafts. Once a parcel becomes cloudy, the thermodynamic properties and the exchange of mass between the cloud and environment are calculated using a cloud model within the CuP framework. The primary advantages of the new scheme are the prediction of cloud-base mass flux, cloud cover, and a range of cloud-top heights.