Discussion of the U.S. Navy's Global Ocean Forecasting Capability

An overview of the Global Ocean Forecasting System (GOFS) efforts taking place at the Naval Research Laboratory, Stennis Space Center, MS are presented. GOFS 3.0 is based on the HYbrid Coordinate Ocean Model (HYCOM) and assimilates a variety of observations via the Navy Coupled Ocean Data Assimilation System (NCODA). This system has horizontal resolution of ~9 km at the equator (~3 km at high latitudes and 32 layers in the vertical. HYCOM has a unique vertical coordinate configuration based on the layered continuity equation that dynamically changes is space and time between isopycnals in the open stratified ocean, z-coordinates in the unstratified ocean and mixed layer and sigma coordinates in shallow water. The system assimilates observations on a 24 hour sequential updating cycle and produces a 5 day forecast once per day. GOFS 3.1 is currently under development and will be based on 3.0 but will include the two-way coupled Community Ice CodE (CICE) model, use 3-D variational assimilation (instead of multi-variate optimal interpolation), and will include an improved methodology for the downward projection of surface observations (so-called synthetic profiles). Plans are for GOFS 3.1 to be be upgraded to GOFS 3.5 during 2015. The primary enhancements will be doubling the horizontal resolution to 1/25 degree (~4 km at the equator), increasing the vertical resolution to 41 layers, and the inclusion of tidal forcing.