3CMI Examining Impacts of Wave Coupling on the Future Global Forecast System

The Unified Forecast System (UFS) is a community based coupled modeling system designed to simplify the National Weather Service suite of models. The Global Forecast System (GFS) is one of these applications, providing global deterministic forecasts out to 16 days. The current version of the GFS (GFSv16) is a one-way coupled model with feedback from the atmospheric model to the wave model. The next version of the GFS will add ocean and sea ice components, and add feedback from the wave model to the other components. This project examines the impact of wave feedback on the coupled model. To analyze the differences, two configurations of the global coupled UFS model were run with atmosphere, land, ocean, ice, and wave components. The “two-way” coupled configuration includes wave feedback and the “one-way” coupled does not. Each configuration was run for 16 days for 2 initial condition dates, 2/13/2020 00z and 9/13/2020 00z. These dates were chosen as examples of high impact events, as the first has Winter storm Dennis, an intense extratropical cyclone affecting parts of Northern Europe, and the second has Hurricane Teddy, a category 4 hurricane affecting the East coast of the US and Canada. Output from each run was analyzed, with a focus on examining the impacts of wave coupling on sea surface temperature, significant wave height, and the drag coefficient over the ocean.