Preprints
https://doi.org/10.5194/gmd-2020-38
https://doi.org/10.5194/gmd-2020-38

Submitted as: model description paper 14 Apr 2020

Submitted as: model description paper | 14 Apr 2020

Review status: a revised version of this preprint is currently under review for the journal GMD.

The GF Convection Parameterization: recent developments, extensions, and applications

Saulo R. Freitas1,2, Georg A. Grell3, and Haiqin Li3,4 Saulo R. Freitas et al.
  • 1Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD, USA
  • 2Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 3Earth Systems Research Laboratory of the National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 4Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA

Abstract. We detail recent developments in the GF (Grell and Freitas, 2014, Freitas et al., 2018) convection parameterization and applications. The parameterization has been extended to a trimodal spectral size to simulate the interaction and transition from shallow, congestus and deep convection regimes. Another main new feature is the inclusion of a closure for non-equilibrium convection that resulted in a substantial gain of realism in the simulation of the diurnal cycle of convection, mainly associated with boundary layer forcing over the land. Additional changes include the transport of momentum, the use of three Probability Density Functions (PDF's) to describe the normalized vertical mass flux profiles from deep, congestus, and shallow plumes (respectively) in the grid box, and the option of using temporal and spatial correlations to stochastically perturb PDF's, momentum transport and the closures. Cloud water detrainment is proportional to mass detrainment and in-cloud hydrometeor mixing ratio, and transport of chemical constituents (including wet deposition) can be treated inside the GF scheme. Transport is handled in flux form and is mass conserving. Finally, the cloud microphysics has been extended to include the ice phase to simulate the conversion from liquid water to ice in updrafts with resulting additional heating release, and the melting from snow to rain within a user-specified melting vertical layer.

Saulo R. Freitas et al.

 
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Saulo R. Freitas et al.

Saulo R. Freitas et al.

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Short summary
Convection Parameterization is a component of atmospheric models aiming to represent the statistical effects of sub-grid scale convective clouds. Because the atmosphere contains circulations with a broad spectrum of scales, the truncation needed to run models in computers requires the introduction of parameterizations to account for processes that are not explicitly resolved. We detail recent developments in the Grell-Freitas CP, which has been applied in several regional and global models.