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Registros recuperados: 8
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Effects of the submesoscale on the potential vorticity budget of ocean mode waters 5
Wenegrat, Jacob O.; Thomas, Leif N.; Gula, Jonathan; Mcwilliams, James C..
Non-conservative processes change the potential vorticity (PV) of the upper ocean, and later, through the subduction of surface waters into the interior, affect the general ocean circulation. Here we focus on how boundary layer turbulence, in the presence of submesoscale horizontal buoyancy gradients, generates a source of potential vorticity at the ocean surface through a balance known as the Turbulent ThermalWind. This source of PV injection at the submesoscale can be of similar magnitude to PV fluxes from the wind and surface buoyancy fluxes, and hence can lead to a net injection of PV onto outcropped isopycnals even during periods of surface buoyancy loss. The significance of these dynamics is illustrated using a high-resolution realistic model of the...
Tipo: Text Palavras-chave: Ageostrophic circulations; Atmosphere-ocean interaction; Fronts; Ocean dynamics; Potential vorticity; Boundary layer.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00452/56347/57937.pdf
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Interaction between an eddy and a zonal jet - Part I. One-and-a-half-layer model 5
Vandermeirsch, Frederic; Carton, Xavier; Morel, Yves.
The interaction between a stable zonal jet and a vortex is studied numerically with two one-and-a-half layer models, one with quasi-geostrophic dynamics, the other with shallow-water equations. In both models, simulations on the f-plane evidence three regimes occuring with increasing vortex strength: (regime 1) weak vortices do not cross the jet and steadily drift along it; (regime 2) stronger vortices cross the jet, tear an opposite-sign meander from the jet with which they pair as a dipole; the trajectory of this dipole depends on the strength of the initial vortex; since most dipoles are asymmetric, they veer back towards the jet axis where they are split apart in the ambient shear; (regime 3) even stronger vortices cross the jet and tear a vorticity...
Tipo: Text Palavras-chave: Potential vorticity; Vortices; Jets; Nonlinear equations; Stratified flow; Rotating fluids.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/2003/publication-440.pdf
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Interaction between an eddy and a zonal jet - Part II. Two-and-a-half-layer model 5
Vandermeirsch, Frederic; Carton, Xavier; Morel, Yves.
In a two-and-a-half-layer quasi-geostrophic model, a process study is conducted on the interaction between a vortex and a zonal jet, both with constant potential vorticity. The vortex is a stable anticyclone, initially located north of the eastward jet. The potential vorticity of the jet is allowed to have various vertical structures, while the vortex is concentrated in only one layer. The flow parameters are set to values characteristic of the Azores region. First, the jet is stable. Weak vortices steadily drift north of the jet without crossing it while strong vortices can cross the jet and tear off a cyclone with which they pair as a heton (baroclinic dipole). This heton often breaks later in the shear exerted by the jet; the two vortices finally...
Tipo: Text Palavras-chave: Potential vorticity; Vortices; Jets; Nonlinear equations; Stratified flow; Rotating fluids.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/2003/publication-441.pdf
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Potential Vorticity diagnostics based on balances between volume integral and boundary conditions 5
Morel, Yves; Gula, Jonathan; Ponte, Aurelien.
Taking advantage of alternative expressions for potential vorticity (PV) in divergence forms, we derive balances between volume integral of PV and boundary conditions, that are then applied to practical computations of PV: • we propose a new method for diagnosing the Ertel potential vorticity from model output, that preserves the balances; • we show how the expression of PV can be derived in general coordinate systems. This is here emphasised with isopycnic coordinates by generalising the PV expression to the general Navier-Stokes equations; • we propose a generalised derivation for the Haynes-McIntyre impermeability theorem, which highlights the role of the bottom boundary condition choice (e.g. no-slip vs free-slip) and mixing near the bottom boundary...
Tipo: Text Palavras-chave: Potential vorticity; Boundary conditions; General circulation; Vortex; Fronts; Boundary layers.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00494/60525/63988.pdf
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Propagation 3D d'ondes inertielles au sein d'un champ turbulent mésoéchelle 5
Danioux, Eric.
A current problem in physical oceanography is to identify the sources of energy at the origin of the abyssal mixing associated with thermohaline circulation. An important source is the inertial waves generated by wind. However, the mechanisms driving this energy from the surface to the deep mixing remain poorly understood. We study here the tridimensional propagation of inertial waves in a fully turbulent mesoscale eddy field with a primitive equations numerical model. After presenting a review of works to date, we describe various methods for extracting the inertial signal. The 3D propagation of inertial waves is then described and rationalized. In particular, two dramatic maxima of the vertical velocity have been found around 100 m and 1700 m. The deep...
Tipo: Text Palavras-chave: Potential vorticity; Diapycnal mixing; Thermohaline circulation; Resonance; Inertial waves; Vorticité potentielle; Mélange diapycnal; Circulation thermohaline; Résonance; Ondes inertielles.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/these-4933.pdf
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Reconstruction of the 3-D Dynamics From Surface Variables in a High-Resolution Simulation of North Atlantic 5
Fresnay, S.; Ponte, Aurelien; Le Gentil, Sylvie; Le Sommer, J..
Several methods that reconstruct the three-dimensional ocean dynamics from sea level are presented and evaluated in the Gulf Stream region with a 1/60° realistic numerical simulation. The use of sea level is motivated by its better correlation with interior pressure or quasigeostrophic potential vorticity (PV) compared to sea surface temperature and sea surface salinity, and, by its observability via satellite altimetry. The simplest method of reconstruction relies on a linear estimation of pressure at depth from sea level. Another method consists in linearly estimating PV from sea level first and then performing a PV inversion. The last method considered, labeled SQG for surface quasigeostrophy, relies on a PV inversion but assumes no PV anomalies. The...
Tipo: Text Palavras-chave: Ocean dynamics; Quasi-geostrophy; Potential vorticity; Sea surface height; Correlation analysis; Spectral analysis.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00425/53632/54468.pdf
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The Role of Curvature in Modifying Frontal Instabilities. Part I: Review of Theory and Presentation of a Nondimensional Instability Criterion 5
Buckingham, Christian; Gula, Jonathan; Carton, Xavier.
In this study, we examine the role of curvature in modifying frontal stability. We first evaluate the classical criterion that the Coriolis parameter f multiplied by the Ertel potential vorticity (PV) q is positive for stable flow and that instability is possible when this quantity is negative. The first portion of this statement can be deduced from Ertel’s PV theorem, assuming an initially positive fq. Moreover, the full statement is implicit in the governing equation for the mean geostrophic flow, as the discriminant, fq, changes sign. However, for curved fronts in cyclogeostrophic or gradient wind balance (GWB), an additional term enters the discriminant owing to conservation of absolute angular momentum L. The resulting expression, (1 + Cu)fq < 0 or...
Tipo: Text Palavras-chave: Instability; Ocean dynamics; Potential vorticity; Turbulence; Frontogenesis/frontolysis; Fronts; Vortices; Angular momentum.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00677/78920/81288.pdf
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The Role of Curvature in Modifying Frontal Instabilities. Part II: Application of the Criterion to Curved Density Fronts at Low Richardson Numbers 5
Buckingham, Christian; Gula, Jonathan; Carton, Xavier.
We continue our study of the role of curvature in modifying frontal stability. In Part I, we obtained an instability criterion valid for curved fronts and vortices in gradient wind balance (GWB): Φ′ = L′q′ < 0, where L′ and q′ are the nondimensional absolute angular momentum and Ertel potential vorticity (PV), respectively. In Part II, we investigate this criterion in a parameter space representative of low-Richardson-number fronts and vortices in GWB. An interesting outcome is that, for Richardson numbers near 1, anticyclonic flows increase in q′, while cyclonic flows decrease in q′, tending to stabilize anticyclonic and destabilize cyclonic flow. Although stability is marginal or weak for anticyclonic flow (owing to multiplication by L′), the...
Tipo: Text Palavras-chave: Eddies; Fronts; Instability; Ocean circulation; Potential vorticity; Frontogenesis/frontolysis; Vortices; Angular momentum.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00677/78919/81286.pdf
Registros recuperados: 8
Primeira ... 1 ... Última
 

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