A Kinematic Kinetic Energy Backscatter Parametrization: From Implementation to Global Ocean Simulations

Wind generated near-inertial waves (NIWs) are a major source of energy for deep-ocean mixing by transmitting wind energy from the ocean surface into the interior. Recently, it has been established that the NIW energy transmission to ocean depths is significantly modulated by background mesoscale vorticity. Thus, understanding NIW energetics in the presence of mesoscale eddies on a global scale is crucial.We study the generation, propagation and dissipation of NIWs in global 1/25o Hybrid Coordinate Ocean Model (HYCOM) simulations with realistic tidal forcing. The model has 41 layers with uniform vertical coordinates in the mixed layer and isopycnal coordinates in the ocean interior. The model is forced by 1/3hr wind from the NAVGEM atmospheric model. We analyze one month of model data for May-June 2019. The 3D HYCOM fields are projected on vertical normal modes to compute the wind input, wave kinetic energy (KE), flux divergence and dissipation per mode.We find that the globally integrated wind input in surface near-inertial motions is 0.21 TW for the 30-day period and is consistent with previous studies. The sum of the wind input to the first 5 modes accounts to only 31% of the total wind input while the sum of the NIW kinetic energy in the first 5 modes adds up to 60% of the total NIW KE. The difference in the fraction of the total between the wind input and NIW KE (31% and 60%) suggests that a significant portion of wind-induced near-inertial motions is dissipated close to the surface without being projected onto modes. We also find that NIW horizontal fluxes diverge from areas with cyclonic vorticity and converge in areas with anticyclonic vorticity, i.e., anticyclonic eddies are a sink for NIW energy in the global ocean.The residual NIW KE that does not project onto modes is found to be largely trapped in anticyclonic eddies. In a next step, we will study the fate of this energy, which most likely propagate downward as beam-like features with large wave numbers. We will compute the near-inertial wave energy balance for fixed subsurface layers and consider the energy exchange between these layers to understand the vertical structure of NIW energy dissipation. We find that the downward NIW radiation to the ocean interior at 500 m depth is 19% of the surface near-inertial wind input for the 30-day period.

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A synthesis of upper ocean geostrophic kinetic energy spectra from a global submesoscale permitting simulation

10.5194/egusphere-egu21-19 ◽

2021 ◽

Author(s):

Hemant Khatri ◽

Stephen Griffies ◽

Takaya Uchida ◽

Han Wang ◽

Dimitris Menemenlis

Keyword(s):

Kinetic Energy ◽

Mixed Layer ◽

Seasonal Variability ◽

Ocean Model ◽

Global Ocean ◽

Upper Ocean ◽

Late Winter ◽

Second Phase ◽

Ocean Turbulence ◽

Two Phases

In the upper ocean, submesoscale turbulence shows seasonal variability and is pronounced in winter. We analyze geostrophic KE spectra in a submesoscale-permitting global ocean model to study the seasonal variability in the upper ocean turbulence. Submesoscale processes peak in winter and, consequently, geostrophic kinetic energy (KE) spectra tend to be relatively shallow in winter (k-2) with steeper spectra in summer (k-3). The roles of frontogenesis processes and mixed-layer instabilities in submesoscale turbulence and their effects on the evolution of KE spectra over an annual cycle are discussed. It is shown that this transition in KE spectral scaling has two phases. In the first phase (late autumn), KE spectra show a presence of two spectral regimes: k-3 scaling in mesoscales (100-300 km) and k-2&#160;scaling in submesoscales (< 50 km), indicating the coexistence of QG, surface-QG, and frontal dynamics. In the second phase (late winter), mixed-layer instabilities convert available potential energy into KE, which cascades upscale leading to flattening of the KE spectra at larger scales, and k-2 power-law develops in mesoscales too.

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Integrated kinetic energy of Atlantic tropical cyclones in a global ocean surface wind analysis

International Journal of Climatology ◽

10.1002/joc.5450 ◽

2018 ◽

Vol 38 (6) ◽

pp. 2651-2661 ◽

Cited By ~ 2

Author(s):

Sean Buchanan ◽

Vasubandhu Misra ◽

Amit Bhardwaj

Keyword(s):

Kinetic Energy ◽

Tropical Cyclones ◽

Surface Wind ◽

Ocean Surface ◽

Global Ocean ◽

Wind Analysis ◽

Ocean Surface Wind

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Inverse Cascades of Kinetic Energy as a Source of Intrinsic Variability: A Global OGCM Study

Journal of Physical Oceanography ◽

10.1175/jpo-d-17-0136.1 ◽

2018 ◽

Vol 48 (6) ◽

pp. 1385-1408 ◽

Cited By ~ 20

Author(s):

Guillaume Sérazin ◽

Thierry Penduff ◽

Bernard Barnier ◽

Jean-Marc Molines ◽

Brian K. Arbic ◽

...

Keyword(s):

Kinetic Energy ◽

Time Scales ◽

Spatial Scales ◽

Baroclinic Instability ◽

Mesoscale Eddy ◽

Low Frequency ◽

Global Ocean ◽

Intrinsic Variability ◽

Inverse Cascade ◽

Wide Range

AbstractA seasonally forced 1/12° global ocean/sea ice simulation is used to characterize the spatiotemporal inverse cascade of kinetic energy (KE). Nonlinear scale interactions associated with relative vorticity advection are evaluated using cross-spectral analysis in the frequency–wavenumber domain from sea level anomaly (SLA) time series. This analysis is applied within four eddy-active midlatitude regions having large intrinsic variability spread over a wide range of scales. Over these four regions, mesoscale surface KE is shown to spontaneously cascade toward larger spatial scales—between the deformation scale and the Rhines scale—and longer time scales (possibly exceeding 10 years). Other nonlinear processes might have to be invoked to explain the longer time scales of intrinsic variability, which have a substantial surface imprint at midlatitudes. The analysis of a fully forced 1/12° hindcast shows that low-frequency and synoptic atmospheric forcing barely affects this inverse KE cascade. The inverse cascade is also at work in a 1/4° simulation, albeit with a weaker intensity, consistent with the weaker intrinsic variability found at this coarser resolution. In the midlatitude North Pacific, the spatiotemporal cascade transfers KE from high-frequency frontal Rossby waves (FRWs), probably generated by baroclinic instability, toward the lower-frequency, westward-propagating mesoscale eddy (WME) field. The WMEs provide local gradients of potential vorticity that support these short Doppler-shifted FRWs. FRWs have periods shorter than 2 months and might be subsampled by altimetric observations, perhaps explaining why the temporal inverse cascade deduced from high-resolution models and mapped altimeter products can be quite different. The nature of the nonlinear interactions between FRWs and WMEs remains unclear but might involve wave turbulence processes.

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Energetics of the layer-thickness form drag based on an integral identity

Ocean Science ◽

10.5194/os-2-161-2006 ◽

2006 ◽

Vol 2 (2) ◽

pp. 161-171 ◽

Cited By ~ 12

Author(s):

H. Aiki ◽

T. Yamagata

Keyword(s):

Kinetic Energy ◽

Layer Thickness ◽

Ocean Circulation ◽

Global Ocean ◽

Weighted Mean ◽

Form Drag ◽

Mean Velocity ◽

Energy Diagram ◽

Pile Up ◽

The Mean

Abstract. The vertical redistribution of the geostrophic momentum by the residual effects of pressure perturbations (called the layer-thickness form drag) is investigated using thickness-weighted temporal-averaged mean primitive equations for a continuously stratified fluid in an adiabatic formulation. A four-box energy diagram, in which the mean and eddy kinetic energies are defined by the thickness-weighted mean velocity and the deviation from it, respectively, shows that the layer-thickness form drag reduces the mean kinetic energy and endows the eddy field with an energy cascade. The energy equations are derived using an identity (called the "pile-up rule") between cumulative sums of the Eulerian mean quantity and the thickness-weighted mean quantity in each vertical column. The pile-up rule shows that the thickness-weighted mean velocity satisfies a no-normal-flow boundary condition at the top and bottom of the ocean, which enables the volume budget of pressure flux divergence in the energy diagram to be determined. With the pile-up rule, the total kinetic energy based on the Eulerian mean can be rewritten in a thickness-weighted form. The four-box energy diagram in the present study should be consistent with energy diagrams of layer models, the temporal-residual-mean theory, and Iwasaki's atmospheric theory. Under certain assumptions, the work of the layer-thickness form drag in the global ocean circulation is suggested to be comparable to the work done by the wind forcing.

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Three-Dimensional, Space-Dependent Mesoscale Diffusivity: Derivation and Implications

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0123.1 ◽

2019 ◽

Vol 49 (4) ◽

pp. 1055-1074 ◽

Cited By ~ 2

Author(s):

V. M. Canuto ◽

Y. Cheng ◽

A. M. Howard ◽

M. S. Dubovikov

Keyword(s):

Kinetic Energy ◽

Drift Velocity ◽

Dimensional Space ◽

Three Dimensional ◽

Deep Ocean ◽

Drake Passage ◽

Eddy Kinetic Energy ◽

Global Ocean ◽

Meridional Heat Transport ◽

Temperature Drift

AbstractRecently, we presented a parameterization of an arbitrary tracer 3D mesoscale flux that describes both diabatic and adiabatic regimes without using arbitrary tapering functions. However, we did not parameterize the mesoscale diffusivity, which is the subject of this work. A key difference between the present and previous diffusivity parameterizations is that in the latter, the two main ingredients, mesoscale drift velocity and eddy kinetic energy, were not parameterized but determined using present data, which deprives the models of predictive power. Since winds, stratification, etc., are predicted to change in the future, use of these parameterizations to study future climate scenarios becomes questionable. In this work, we parameterize drift velocity and eddy kinetic energy (vertical–horizontal components), which we first assess with data [WOCE, TOPEX/Poseidon (T/P), and North Atlantic Tracer Release Experiment (NATRE)] and then use in a coarse-resolution stand-alone ocean code under Coordinated Ocean-Ice Reference Experiment I (CORE-I) forcing. We present results for the global ocean temperature and salinity, Atlantic overturning circulation, meridional heat transport, and Drake Passage transport, which we compare with several previous studies. The temperature drift is less than that of five of seven previous OGCMs, and the salinity drift is among the smallest in those studies. The predicted winter Antarctic Circumpolar Current mixed layer depths (MLDs) are in good agreement with the data. Predicting the correct MLD is important in climate studies since models that predict very deep mixed layers transfer more of the radiative perturbation to the deep ocean, reducing surface warming (and vice versa).

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Energetics of the layer-thickness form drag based on an integral identity

Ocean Science Discussions ◽

10.5194/osd-3-541-2006 ◽

2006 ◽

Vol 3 (3) ◽

pp. 541-568 ◽

Cited By ~ 1

Author(s):

H. Aiki ◽

T. Yamagata

Keyword(s):

Kinetic Energy ◽

Layer Thickness ◽

Ocean Circulation ◽

Global Ocean ◽

Weighted Mean ◽

Form Drag ◽

Mean Velocity ◽

Energy Diagram ◽

Pile Up ◽

The Mean

Abstract. The vertical redistribution of the geostrophic momentum by the residual effects of pressure perturbations (called the layer-thickness form drag) is investigated using thickness-weighted temporal-averaged mean primitive equations for a continuously stratified fluid in an adiabatic formulation. A four-box energy diagram, in which the mean and eddy kinetic energies are defined by the thickness-weighted mean velocity and the deviation from it, respectively, shows that the layer-thickness form drag reduces the mean kinetic energy and endows the eddy field with an energy cascade. The energy equations are derived using an identity (called the "pile-up rule'') between cumulative sums of the Eulerian mean quantity and the thickness-weighted mean quantity in each vertical column. The pile-up rule shows that the thickness-weighted mean velocity satisfies a no-normal-flow boundary condition at the top and bottom of the ocean, which enables the volume budget of pressure flux divergence in the energy diagram to be determined. With the pile-up rule, the total kinetic energy based on the Eulerian mean can be rewritten in a thickness-weighted form. The four-box energy diagram in the present study should be consistent with energy diagrams of layer models, the temporal-residual-mean theory, and Iwasaki's atmospheric theory. Under certain assumptions, the work of the layer-thickness form drag in the global ocean circulation is suggested to be comparable to the work done by the wind forcing.

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