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


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.

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