The GFS model physics has long included the parameterization of subgrid-scale drag forces and dissipative heating due to the vertical propagation and breaking of gravity waves forced by topography and non-stationary sources such as convection. Two additional parameterizations of orographic sources of subgrid drag have recently been implemented in the RAP/HRRR regional forecasting models developed by the Global Systems Laboratory (GSL). These schemes, which represent gravity wave breaking in highly stable boundary layers and turbulent orographic form drag, account for drag forces generated by horizontal topographic variations down to the ~1km scale. All of these schemes are now available in one “unified” physics module within the FV3GFS/CCPP framework. This presentation will provide a physical overview of the parameterizations. Preliminary test results with the global FV3GFS will be presented, and some possible future directions will be described.
