On the interplay between horizontal resolution and wave drag and their effect on tidal baroclinic mode waves in realistic global ocean simulations

Type Article
Date 2020-08
Language English
Author(s) Buijsman Maarten C.1, Stephenson Gordon R.1, Ansong Joseph K.2, Arbic Brian K.3, Green J.A. Mattias4, Richman James G.5, Shriver Jay F.6, Vic Clement7, Wallcraft Alan J.5, Zhao Zhongxiang8
Affiliation(s) 1 : School of Ocean Science and Engineering, University of Southern Mississippi, Stennis Space Center, MS, USA
2 : Department of Mathematics, University of Ghana, Accra, Ghana
3 : Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
4 : School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, UK
5 : Center for Ocean-Atmospheric Prediction Studies, Florida State University, Tallahassee, FL, USA
6 : Naval Research Laboratory, Stennis Space Center, MS, USA
7 : University of Brest, CNRS, IRD, Ifremer, Laboratoire d’Océanographie Physique et Spatiale, Plouzané, Bretagne, France
8 : Applied Physics Laboratory, University of Washington, Seattle, WA, USA
Source Ocean Modelling (1463-5003) (Elsevier BV), 2020-08 , Vol. 152 , P. 101656 (17p.)
DOI 10.1016/j.ocemod.2020.101656
WOS© Times Cited 2
Keyword(s) Numerical models, Internal tides, Wave damping, Vertical modes

The effects of horizontal resolution and wave drag damping on the semidiurnal M tidal energetics are studied for two realistically-forced global HYbrid Coordinate Ocean Model (HYCOM) simulations with 41 layers and horizontal resolutions of 8 km (; H12) and 4 km (; H25). In both simulations, the surface tidal error is minimized by tuning the strength of the linear wave drag, which is a parameterization of the surface-tide energy conversion to the unresolved baroclinic wave modes. In both simulations the M surface tide error with TPXO8-atlas, an altimetry constrained model, is 2.6 cm. Compared to H12, the surface tide energy conversion to the resolved vertical modes is increased by 50% in H25. This coincides with an equivalent reduction in the tuned loss of energy from the surface tide to the wave drag. For the configurations studied here, the horizontal and not the vertical resolution is the factor limiting the number of vertical modes that are resolved in most of the global ocean: modes 1–2 in H12 and modes 1–5 in H25. The wave drag also dampens the resolved internal tides. The 40% reduction in wave-drag strength does not result in a proportional increase in the mode-1 energy density in H25. In the higher-resolution simulations, topographic mode-scattering and wave–wave interactions are better resolved. This allows for an energy flux out of mode 1 to the higher modes, mitigating the need for an internal tide damping term. The HYCOM simulations are validated with analytical conversion models and altimetry-inferred sea-surface height, fluxes, and surface tide dissipation. H25 agrees best with these data sets to within 10%. To facilitate the comparison of stationary tide signals extracted from time series with different durations, we successfully apply a spatially-varying correction factor.

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Buijsman Maarten C., Stephenson Gordon R., Ansong Joseph K., Arbic Brian K., Green J.A. Mattias, Richman James G., Shriver Jay F., Vic Clement, Wallcraft Alan J., Zhao Zhongxiang (2020). On the interplay between horizontal resolution and wave drag and their effect on tidal baroclinic mode waves in realistic global ocean simulations. Ocean Modelling, 152, 101656 (17p.). Publisher's official version : https://doi.org/10.1016/j.ocemod.2020.101656 , Open Access version : https://archimer.ifremer.fr/doc/00640/75199/