Global Ocean Prediction Using HYCOM

In the third year of this project, fully-global eddy- resolving simulations have been performed using the HYbrid Coordinate Ocean Model (HYCOM) at 1/12deg (~7 km mid-latitude) resolution. HYCOM is isopycnal in the open, stratified ocean, but makes a dynamically smooth transition to a terrain-following coordinate in shallow water and to pressure coordinates in the mixed layer and/or unstratified regions via the layered continuity equation. This approach incorporates the advantages of these three distinct vertical coordinate types into one ocean model that includes the deep ocean as well as coastal regions. In addition, it is designed for high vertical resolution in the surface mixed layer. The majority of the first and second year simulations were atmospherically forced only (no data assimilation). In the second year and third year we added cases with ocean data assimilation. Since December 2006 we have run a nowcast every day, and since February 2007 we perform a nowcast and a 3-day forecast every day in real time. Results from HYCOM´s data-assimilative hindcast of 2004 are compared to observations and to the existing operational nowcast/forecast system at the Naval Oceanographic Office.