Articles | Volume 5, issue 6
Geosci. Model Dev., 5, 1407–1423, 2012
Geosci. Model Dev., 5, 1407–1423, 2012

Development and technical paper 14 Nov 2012

Development and technical paper | 14 Nov 2012

Unified parameterization of the planetary boundary layer and shallow convection with a higher-order turbulence closure in the Community Atmosphere Model: single-column experiments

P. A. Bogenschutz1, A. Gettelman1, H. Morrison1, V. E. Larson2, D. P. Schanen2, N. R. Meyer2, and C. Craig1 P. A. Bogenschutz et al.
  • 1National Center for Atmospheric Research, Boulder, Colorado, USA
  • 2University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA

Abstract. This paper describes the coupling of the Community Atmosphere Model (CAM) version 5 with a unified multi-variate probability density function (PDF) parameterization, Cloud Layers Unified by Binormals (CLUBB). CLUBB replaces the planetary boundary layer (PBL), shallow convection, and cloud macrophysics schemes in CAM5 with a higher-order turbulence closure based on an assumed PDF. Comparisons of single-column versions of CAM5 and CAM-CLUBB are provided in this paper for several boundary layer regimes. As compared to large eddy simulations (LESs), CAM-CLUBB and CAM5 simulate marine stratocumulus regimes with similar accuracy. For shallow convective regimes, CAM-CLUBB improves the representation of cloud cover and liquid water path (LWP). In addition, for shallow convection CAM-CLUBB offers better fidelity for subgrid-scale vertical velocity, which is an important input for aerosol activation. Finally, CAM-CLUBB results are more robust to changes in vertical and temporal resolution when compared to CAM5.