CLUBB (Cloud Layers Unified By Binormals) is a parameterization of turbulence and cloud macrophysics in the Earth’s atmosphere.  It is a 1D model that predicts the evolution of fields as a function of altitude (but not horizontal position).  It may be run as a standalone single-column model, or it may be implemented as a subgrid-scale parameterization in a large-scale weather forecast or general circulation model.  CLUBB is the default parameterization in several global models, including CESM2, E3SMv3, and NorESM2.

CLUBB is a unified parameterization.  It uses a single algorithm to model many cloud types, such as cumulus, stratocumulus, cumulus-rising-into-stratocumulus, and Arctic clouds.  In addition, it models clear convective boundary layers and stably stratified boundary layers.  It is being generalized to handle deep convective clouds.

CLUBB is based on the assumed PDF method.  It estimates the subgrid-scale probability density function (PDF) of moisture, heat content, and turbulence within each grid box at each model timestep.  This PDF can be used to consistently diagnose several useful quantities such as cloud fraction and buoyancy flux.

CLUBB uses semi-implicit time stepping.  This lengthens the allowable time step and thereby makes CLUBB affordable in global simulations.

CLUBB is being co-developed by researchers at University of Wisconsin — Milwaukee and researchers elsewhere.  CLUBB’s source code is freely available at https://github.com/larson-group/clubb_release.

References:  Larson (2017); Golaz et al. (2002); Larson et al. (2002); Larson and Golaz (2005).