Improvements to Boundary-Layer Representation in Convection-Resolving Global-to-Regional Forecasts using GFDL fvGFS

The nesting capabilities in the FV3 dynamical core allow us to efficiently reach convection-resolving scales while preserving the large-scale circulation of a global model. Improvements to the physics will be needed to best take advantage of the potential hurricane forecast gains from very high resolution, but care must be taken to not simultaneously degrade the large-scale state, critical for accurate track prediction. Higher horizontal resolutions demand higher vertical resolution as well, especially in the planetary boundary layer (PBL).

We describe improvements made to the GFDL finite-volume Global Forecast System (fvGFS), a model made up of FV3 coupled to augmented GFS physics. The new "vertical nesting" capability in FV3 permits us to optimize our vertical resolution in the high-resolution region, allowing us to better represent PBL processes critical for intensification. We also describe fundamental improvements in the PBL schemes available to fvGFS, which will help improve thermodynamic profiles and boundary layer structure.

Prospects for further unification of models---global to regional, across timescales, and the oft-overlooked tropical-to-extratropical---will also be discussed.