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a b s t r a c tThis paper presents a five-year global simulation of HYCOM, the HYbrid Coordinate Ocean Model, that simultaneously resolves the eddying general circulation, barotropic tides, and baroclinic tides with 32 layers in the vertical direction and 1/12.5°(equatorial) horizontal grid spacing. A parameterized topographic wave drag is inserted into the model and tuned so that the surface tidal elevations are of comparable accuracy to those in optimally tuned forward tide models used in previous studies. The model captures 93% of the open-ocean sea-surface height variance of the eight largest tidal constituents, as recorded by a standard set of 102 pelagic tide gauges spread around the World Ocean. In order to minimize the impact of the wave drag on non-tidal motions, the model utilizes a running 25-h average to approximately separate tidal and non-tidal components of the near-bottom flow. In contrast to earlier high-resolution global baroclinic tide simulations, which utilized tidal forcing only, the simulation presented here has a horizontally non-uniform stratification, supported by the wind-and buoyancy forcing. The horizontally varying stratification affects the baroclinic tides in high latitudes to first order. The magnitude of the internal tide perturbations to sea surface elevation amplitude and phase in a large box surrounding Hawai'i is quite similar to that observed in satellite altimeter data, although the exact locations of peaks and troughs in the modeled perturbations differ from those in the observed perturbations.

B y E r i c P. c h a s s i g N E t, h a r l E y E . h u r l B u r t, E . J o s E P h M E t z g E r , o l E M a r t i N s M E d s ta d , J a M E s a . c u M M i N g s ,g E o r g E r . h a l l i w E l l , r a i N E r B l E c k , r E M y B a r a i l l E , The partnership represents a broad spectrum of the oceanographic community, bringing together academia, federal agencies, and industry/commercial entities, and spanning modeling, data assimilation, data management and serving, observational capabilities, and application of HYCOM prediction system outputs. In addition to providing real-time, eddy-resolving global-and basin-scale ocean prediction systems for the US Navy and NOAA, this project also offered an outstanding opportunity for NOAA-Navy collaboration and cooperation, ranging from research to the operational level. This paper provides an overview of the global HYCOM ocean prediction system and highlights some of its achievements. An important outcome of this effort is the capability of the global system to provide boundary conditions to even higherresolution regional and coastal models.Oceanography Vol. In addition to operational eddyresolving global-and basin-scale ocean prediction systems for the US Navy and NOAA, respectively, this project offered an outstanding opportunity for NOAA-Navy collaboration and cooperation ranging from research to the operational level.

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[1] Global comparisons of barotropic and internal tides generated in an eddy-resolving ocean circulation model are made with tidal estimates obtained from altimetric sea surface heights and an altimetry-constrained tide model. As far as we know, our Hybrid Coordinate Ocean Model (HYCOM) simulations shown here and in an earlier paper are the only published high-resolution global simulations to contain barotropic tides, internal tides, the general circulation, and mesoscale eddies concurrently. Comparing the model barotropic tide with a global data-assimilative shallow water tide model shows that the global tidal elevation differences are approximately evenly split between discrepancies in tidal amplitude and phase. Both the model and observations show strong generation of internal tides at a limited number of "hot spot" regions with propagation of beams of energy for thousands of kilometers away from the sources. The model internal tidal amplitudes compare well with observations near these energetic tidal regions. Averaged over these regions, the model and observation internal tide amplitude estimates agree to approximately 15% for the four largest semidiurnal constituents and 23% for the four largest diurnal constituents. Away from the hot spots, the comparison between the model and altimetric amplitude is not as good due, in part, to two problems, errors in the model barotropic tides and overestimation of the altimetric tides in regions of strong mesoscale eddy activity. Examining the general energy distribution of the simulated internal tide is an important first step in the evaluation of internal tides in HYCOM.