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  • 2020-2023  (2)
  • 2020-2022  (4)
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  • 1
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    SPRINGER HEIDELBERG
    In:  EPIC3Ocean Dynamics, SPRINGER HEIDELBERG, 70(8), pp. 1067-1088, ISSN: 1616-7341
    Publication Date: 2020-09-17
    Description: Surface windstress transfers energy to the surface mixed layer of the ocean, and this energy partly radiates as internal gravity waves with near-inertial frequencies into the stratified ocean below the mixed layer where it is available for mixing. Numerical and analytical models provide estimates of the energy transfer into the mixed layer and the fraction radiated into the interior, but with large uncertainties, which we aim to reduce in the present study. An analytical slab model of the mixed layer used before in several studies is extended by consistent physics of wave radiation into the interior. Rayleigh damping, controlling the physics of the original slab model, is absent in the extended model and the wave-induced pressure gradient is resolved. The extended model predicts the energy transfer rates, both in physical and wavenumber-frequency space, associated with the wind forcing, dissipation in the mixed layer, and wave radiation at the base as function of a few parameters: mixed layer depth, Coriolis frequency and Brunt-Väisälä frequency below the mixed layer, and parameters of the applied windstress spectrum. The results of the model are satisfactorily validated with a realistic numerical model of the North Atlantic Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Publication Date: 2020-03-12
    Description: We revisit the challenges and prospects for ocean circulation models following Griffies et al. (2010). Over the past decade, ocean circulation models evolved through improved understanding, numerics, spatial discretization, grid configurations, parameterizations, data assimilation, environmental monitoring, and process-level observations and modeling. Important large scale applications over the last decade are simulations of the Southern Ocean, the Meridional Overturning Circulation and its variability, and regional sea level change. Submesoscale variability is now routinely resolved in process models and permitted in a few global models, and submesoscale effects are parameterized in most global models. The scales where nonhydrostatic effects become important are beginning to be resolved in regional and process models. Coupling to sea ice, ice shelves, and high-resolution atmospheric models has stimulated new ideas and driven improvements in numerics. Observations have provided insight into turbulence and mixing around the globe and its consequences are assessed through perturbed physics models. Relatedly, parameterizations of the mixing and overturning processes in boundary layers and the ocean interior have improved. New diagnostics being used for evaluating models alongside present and novel observations are briefly referenced. The overall goal is summarizing new developments in ocean modeling, including: how new and existing observations can be used, what modeling challenges remain, and how simulations can be used to support observations
    Description: Published
    Description: Article 65
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Physical Oceanography, AMER METEOROLOGICAL SOC, 50(3), pp. 751-771, ISSN: 0022-3670
    Publication Date: 2020-04-20
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Physical Oceanography, AMER METEOROLOGICAL SOC, 50(4), pp. 935-944, ISSN: 0022-3670
    Publication Date: 2020-04-20
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    In:  EPIC3A new, energetically, and dynamically consistent closure for the lee wave drag on the large-scale circulation is developed and tested in idealized and realistic ocean model simulations. The closure is based on the radiative transfer equation for internal, 51(12), pp. 3573-3588
    Publication Date: 2022-07-25
    Description: A new, energetically, and dynamically consistent closure for the lee wave drag on the large-scale circulation is developed and tested in idealized and realistic ocean model simulations. The closure is based on the radiative transfer equation for internal gravity waves, integrated over wavenumber space, and consists of two lee wave energy compartments for up- and downward propagating waves, which can be cointegrated in an ocean model. Mean parameters for vertical propagation, mean–flow interaction, and the vertical wave momentum flux are calculated assuming that the lee waves stay close to the spectral shape given by linear theory of their generation. Idealized model simulations demonstrate how lee waves are generated and interact with the mean flow and contribute to mixing, and document parameter sensitivities. A realistic eddy-permitting global model at 1/10° resolution coupled to the new closure yields a globally integrated energy flux of 0.27 TW into the lee wave field. The bottom lee wave stress on the mean flow can be locally as large as the surface wind stress and can reach into the surface layer. The interior energy transfers by the stress are directed from the mean flow to the waves, but this often reverses, for example, in the Southern Ocean in case of shear reversal close to the bottom. The global integral of the interior energy transfers from mean flow to waves is 0.14 TW, while 0.04 TW is driving the mean flow, but this share depends on parameter choices for nonlinear effects.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
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    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Physical Oceanography, AMER METEOROLOGICAL SOC, 52(7), pp. 1351-1362, ISSN: 0022-3670
    Publication Date: 2022-07-25
    Description: The generation of internal gravity waves from an initially geostrophically balanced flow is diagnosed in nonhydrostatic numerical simulations of shear instabilities for varied dynamical regimes. A nonlinear decomposition method up to third order in the Rossby number (Ro) is used as the diagnostic tool for a consistent separation of the balanced and unbalanced motions in the presence of their nonlinear coupling. Wave emission is investigated in an Eady-like and a jet-like flow. For the jet-like case, geostrophic and ageostrophic unstable modes are used to initialize the flow in different simulations. Gravity wave emission is in general very weak over a range of values for Ro. At sufficiently high Ro, however, when the condition for symmetric instability is satisfied with negative values of local potential vorticity, significant wave emission is detected even at the lowest order. This is related to the occurrence of fast ageostrophic instability modes, generating a wide spectrum of waves. Thus, gravity waves are excited from the instability of the balanced mode to lowest order only if the condition of symmetric instability is satisfied and ageostrophic unstable modes obtain finite growth rates.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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