This nowcast/forecast system is a demonstration product of the HYCOM Consortium for data-assimilative ocean modeling sponsored by the National Ocean Partnership Program and partnering projects funded by the Office of Naval Research, the National Science Foundation, the Department of Energy, and the National Oceanic and Atmospheric Administration. It is run in real time at the Naval Oceanographic Office (NAVOCEANO) DoD Supercomputing Resource Center (DSRC). It uses atmospheric forcing from the Navy Global Environmental Model (NAVGEM).
The HYCOM Consortium is a participant in the multi-national Global Ocean Data Assimilation Experiment (GODAE), including presence on the U. S. and international steering teams. GODAE is aimed at demonstrating real-time global ocean products in a way that will promote wide utility and availability for maximum benefit to the community.
HYCOM is designed as a generalized (hybrid isopycnal/
/z) coordinate
ocean model. It is isopycnal in the open stratified ocean, but reverts
to a terrain-following coordinate in shallow coastal regions, and to
z-level coordinates near the surface in the mixed layer. This
generalized vertical coordinate approach is dynamic in space and time
via the layered continuity equation, which allows a dynamical transition
between the coordinate types. Like MICOM, HYCOM allows isopycnals
intersecting sloping topography by allowing zero thickness layers. HYCOM
was developed from MICOM using the theoretical foundation for
implementing a hybrid coordinate system set forth in Bleck and Boudra
(1981; J. Phys. Oceanogr.), Bleck and Benjamin (1993; Mon. Wea. Rev.),
Bleck (2002; Ocean Modelling), Chassignet et al. (2003, J. Phys. Oceanogr.)
and Halliwell (2003; Ocean Modelling).
HYCOM is maintained as a single scalable/portable source code. The Gulf of Mexico model has 1/25° equatorial resolution and latitudinal resolution of 1/25° cos(lat) or ˜ 3.5 km for each variable at mid-latitudes. It has 20 coordinate surfaces in the vertical.
The data assimilation is performed using the Navy Coupled Ocean Data Assimilation (NCODA) (Cummings, 2005; QJRMS) system with a model forecast as the first guess. NCODA assimilates available satellite altimeter observations (along track obtained via the NAVOCEANO Altimeter Data Fusion Center), satellite and in situ sea surface temperature (SST) as well as available in situ vertical temperature and salinity profiles from XBTs, ARGO floats and moored buoys. The present system is using the latest NCODA 3dvar solver. and it also uses first guess at appropriate time (FGAT) for the sea surface temperature analysis.
For more information about HYCOM and the HYCOM Consortium, see the HYCOM web page. The source code is also available from this web page.