Toward a Fully-Coupled Global Ensemble Forecast System (GEFSv13)

NOAA/NCEP will upgrade the operational uncoupled Global Forecast System (GFSv16) and Global Ensemble Forecast System (GEFSv12) to be fully-coupled models at the same time in the future. A UFS-based 6-way (atmosphere, ocean, sea ice, land, wave, aerosol) fully-coupled forecast system is being developed targeting these implementations. A series of coupled model prototypes have been performed as part of model development. In the meantime, several coupled ensemble prototypes (EPs) were also developed and performed based on these coupled model prototypes with updates and tuning of stochastic physics schemes as well as other changes to model configurations. One of the big challenges in developing coupled GEFSv13 is to quantify the model uncertainties following the updates of model physics. As the impact of SPPT (stochastic Perturbed Parameterization Tendencies) largely depends on the model's physical tendency, the configuration of the SPPT scheme needs to be tuned accordingly when the magnitude of the model physical tendency changes significantly due to physics updates.

In this presentation, we will show some results from five ensemble prototypes EP1-EP4 and EP4a (EP4 with aerosol) and compare them with operational GEFSv12.