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Concurrent simulation of tides and the general circulation in an eddy-resolving global ocean model
Brian K. Arbic, E. Joseph Metzger, Alan J. Wallcraft
Florida State University
(Abstract received 04/06/2009 for session X)
ABSTRACT
This paper presents a 5-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 one-twelveth degree 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 percent 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-hour average to roughly separate tidal and non-tidal components of the bottom flow. In contrast to earlier high-resolution global baroclinic tide simulations, which utilized tidal forcing only, the run 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 height around Hawaii is quite similar to that seen in satellite altimeter data, although the exact locations of peaks and troughs in the model differ from those seen in the altimeter. Images of eddies and internal tides co-existing in the model are shown, and a discussion of planned future analyses that will extend far beyond the preliminary analyses shown here is given.
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2009 LOM Workshop, Miami, Florida Jume 1 - 3, 2009