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Registros recuperados: 12
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Characterization of tracer cascade in physical space ArchiMer
Hua, Bach-lien; Klein, Patrice; Lapeyre, Guillaume.
Geophysical turbulent fluids are characterized by the presence of organized energetic structures which control tracer transport and stirring, while enabling a tracer cascade down to the smallest scales. In order to understand the physical mechanisms involved in this turbulent tracer cascade, we focus on the dynamics underlying the formation of tracer gradients which are necessarily associated to this cascade. We show that the dynamics of tracer gradients in physical space is mainly governed by their orientation with respect to the compressional eigenvector of the strain tensor. This relative angle results from the competition between strain and the "effective rotation" (due to both vorticity and rotation of strain axes). The implication is that tracer...
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Ano: 2001 URL: http://archimer.ifremer.fr/doc/00067/17786/15309.pdf
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Wind ringing of the ocean in presence of mesoscale eddies ArchiMer
Klein, Patrice; Lapeyre, Guillaume; Large, Wg.
Recent findings have highlighted the impact of high frequency (HF) winds on the inertial motions and the consequences on the large-scale oceanic circulation [Wunsch and Ferrari, 2004]. Within this context the present study focuses on the role of intermediate scales related to oceanic mesoscale eddies. Results show that a turbulent eddy field does not affect the impact of HF winds on the inertial motions. However the eddies efficiently and permanently concentrate the wind-forced inertial motions in small-scale anticyclonic structures. This leads to a spatially heterogeneous vertical mixing strongly related to the eddy field properties.
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Ano: 2004 URL: https://archimer.ifremer.fr/doc/00000/10838/9262.pdf
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Impact of the small-scale elongated filaments on the oceanic vertical pump ArchiMer
Lapeyre, Guillaume; Klein, Patrice.
Oceanic mesoscale eddies (with a diameter of 50-100 km) are known to be associated with significant vertical tracer fluxes in the upper few hundred meters. In particular, they are important for the biogeochemical system, accounting for 20-30% of the vertical nutrient transport. However, estimates of the global tracer fluxes neglect the role played by thin elongated filaments (with a width of 5-10 km). These sub-mesoscale structures are produced by eddy interactions and ubiquitous in regions between eddies. We use a Surface Quasi-Geostrophic model to quantify their impact on the net vertical tracer flux into the surface layers. We show that eddy interactions are an important source of tracer injection because they lead to the production of filaments and to...
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Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2459.pdf
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Potential use of microwave sea surface temperatures for the estimation of ocean currents - art. no. L24608 ArchiMer
Isern-fontanet, Jordi; Chapron, Bertrand; Lapeyre, Guillaume; Klein, Patrice.
In this paper, we examine the emerging potential offered by satellite microwave radiometer SST measurements to complement altimeter data to quantitatively derive surface ocean currents. The proposed methodology does not follow standard sequential temporal analysis but follows the application of the Surface Quasi-Geostrophic (SQG) theory. Accordingly, under favourable environmental conditions, the implementation for this methodology is simple and robust, and most importantly, solely requires a single SST image. For the present demonstration, altimetric measurements are used to infer a necessary adjustment to match the kinetic energy level for length scales smaller than 300 km. This helps to derive a regional effective Brunt-Vaisala frequency to produce SQG...
Tipo: Text Palavras-chave: Microwave radiometers; Sea surface temperature; Surface quasi geostrophy.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2177.pdf
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Tracking coherent structures in a regional ocean model with wavelet analysis: Application to Cape Basin eddies - art. no. C05043 ArchiMer
Doglioli, Andrea; Blanke, Bruno; Speich, Sabrina; Lapeyre, Guillaume.
[1] This study is mainly aimed at proposing objective tools for the identification and tracking of three-dimensional eddy structures. It is conducted with a high-resolution numerical model of the ocean region around South Africa, and emphasis is put on Cape Basin anticyclones and cyclones thought to be actively implicated in the Indian-Atlantic interocean exchange. We settle on wavelet analysis for the decomposition and processing of successive maps of relative vorticity for a simulation run with 1/10 degrees resolution. The identification of three- dimensional coherent structures comes with the calculation of eddy trajectories and the time evolution of eddy properties. Instantaneous mass transport and momentum of eddies are calculated from the knowledge...
Tipo: Text Palavras-chave: Southeast Atlantic ocean; Agulhas current system; Wavelet analysis; Regional modeling; Oceanic eddies.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2684.pdf
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Three-dimensional reconstruction of oceanic mesoscale currents from surface information - art. no. C09005 ArchiMer
Isern-fontanet, Jordi; Lapeyre, Guillaume; Klein, Patrice; Chapron, Bertrand; Hecht, M.
The ability to reconstruct the three-dimensional (3D) dynamics of the ocean by an effective version of Surface Quasi-Geostrophy (eSQG) is examined. Using the fact that surface density plays an analogous role as interior potential vorticity (PV), the eSQG method consists in inverting the QG PV generated by sea-surface density only. We also make the extra assumption that sea-surface temperature (SST) anomalies fully represent surface density anomalies. This approach requires a single snapshot of SST and the setup of two parameters: the mean Brunt-Vaisala frequency and a parameter that determines the energy level at the ocean surface. The validity of this approach is tested using an Ocean General Circulation Model simulation representing the North Atlantic in...
Tipo: Text Palavras-chave: 3D dynamics reconstruction; SST; Surface Quasi Geostrophy.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-4620.pdf
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Surface kinetic energy transfer in surface quasi-geostrophic flows ArchiMer
Capet, Xavier; Klein, Patrice; Hua, Bach-lien; Lapeyre, Guillaume; Mcwilliams, James C.
The relevance of surface quasi-geostrophic dynamics (SQG) to the upper ocean and the atmospheric tropopause has been recently demonstrated in a wide range of conditions. Within this context, the properties of SQG in terms of kinetic energy (KE) transfers at the surface are revisited and further explored. Two well-known and important properties of SQG characterize the surface dynamics: (i) the identity between surface velocity and density spectra (when appropriately scaled) and (ii) the existence of a forward cascade for surface density variance. Here we show numerically and analytically that (i) and (ii) do not imply a forward cascade of surface KE (through the advection term in the KE budget). On the contrary, advection by the geostrophic flow primarily...
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Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-4623.pdf
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Diagnosis of vertical velocities in the upper ocean from high resolution sea surface height ArchiMer
Klein, Patrice; Isern-fontanet, Jordi; Lapeyre, Guillaume; Roullet, G.; Danioux, Eric; Chapron, Bertrand; Le Gentil, Sylvie; Sasaki, H..
A surface Quasi-Geostrophy based (eSQG) method to diagnose the vertical velocity field from Sea Surface Height (SSH) is assessed using high resolution simulations. These simulations concern a turbulent eddy field with large Rossby numbers and energetic wind-driven motions. Results indicate that low-frequency vertical velocities (and also horizontal motions) can be reconstructed within a range of scales between 20 km and 400 km from the surface down to 500 m. The only information needed is a single high-resolution SSH snapshot and information on the large-scale vertical stratification. Inertial motions are naturally filtered because they do not contaminate SSH as we demonstrate. These results are encouraging and further strengthen previous studies using the...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/00000/11094/7418.pdf
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Atmospheric response to sea surface temperature mesoscale structures ArchiMer
Lambaerts, J.; Lapeyre, Guillaume; Plougonven, R.; Klein, Patrice.
Recent studies have revealed that strong sea surface temperature (SST) fronts, on the scale of a Western Boundary Current, significantly affect not just the Marine Boundary Layer but the entire troposphere. This has aroused renewed interest in air-sea interactions. The present study investigates the atmospheric response to fixed SST anomalies associated with mesoscale oceanic eddies and submesoscale filaments, using idealized simulations. Our main result is that in weak wind conditions, the vertical velocity in the planetary boundary layer (PBL) is linearly proportional to the SST Laplacian. This is established by a quantitative analysis in the spatial space as well as in the spectral space. Comparing the responses to two different SST fields shows that...
Tipo: Text Palavras-chave: Air-sea interactions; Boundary layer; Sea surface temperature.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00169/28047/26247.pdf
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Global Observations of Fine-Scale Ocean Surface Topography With the Surface Water and Ocean Topography (SWOT) Mission ArchiMer
Morrow, Rosemary; Fu, Lee-lueng; Ardhuin, Fabrice; Benkiran, Mounir; Chapron, Bertrand; Cosme, Emmanuel; D’ovidio, Francesco; Farrar, J. Thomas; Gille, Sarah T.; Lapeyre, Guillaume; Le Traon, Pierre-yves; Pascual, Ananda; Ponte, Aurelien; Qiu, Bo; Rascle, Nicolas; Ubelmann, Clement; Wang, Jinbo; Zaron, Edward D..
The future international Surface Water and Ocean Topography (SWOT) Mission, planned for launch in 2021, will make high-resolution 2D observations of sea-surface height using SAR radar interferometric techniques. SWOT will map the global and coastal oceans up to 77.6∘ latitude every 21 days over a swath of 120 km (20 km nadir gap). Today’s 2D mapped altimeter data can resolve ocean scales of 150 km wavelength whereas the SWOT measurement will extend our 2D observations down to 15–30 km, depending on sea state. SWOT will offer new opportunities to observe the oceanic dynamic processes at scales that are important in the generation and dissipation of kinetic energy in the ocean, and that facilitate the exchange of energy between the ocean interior and the...
Tipo: Text Palavras-chave: Ocean mesoscale circulation; Satellite altimetry; SAR-interferometry; Tides and internal tides; Calibration-validation.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00495/60685/64181.pdf
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Ocean Scale Interactions from Space ArchiMer
Klein, Patrice; Lapeyre, Guillaume; Siegelman, Lia; Qiu, Bo; Fu, Lee‐lueng; Torres, Hector; Su, Zhan; Menemenlis, Dimitris; Le Gentil, Sylvie.
Satellite observations of the last two decades have led to a major breakthrough emphasizing the existence of a strongly energetic mesoscale turbulent eddy field in all the oceans. This ocean mesoscale turbulence (OMT) is characterized by cyclonic and anticyclonic eddies (with a 100‐‐300 km size and depth scales of ~500‐‐1000 m) that capture approximatively 80% of the total kinetic energy and is now known to significantly impact the large‐scale ocean circulation, the ocean's carbon storage, the air‐sea interactions and therefore the Earth climate as a whole. However, OMT revealed by satellite observations has properties that differ from those related to classical geostrophic turbulence theories. In the last decade, a large number of theoretical and...
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Ano: 2019 URL: https://archimer.ifremer.fr/doc/00488/59951/63202.pdf
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On the Impact of Long Wind-Waves on Near-Surface Turbulence and Momentum Fluxes ArchiMer
Ayet, Alex; Chapron, Bertrand; Redelsperger, Jean-luc; Lapeyre, Guillaume; Marié, Louis.
We propose a new phenomenological model to represent the impact of wind-waves on the dissipation of turbulence kinetic energy near the sea surface. In this model, the momentum flux at a given height results from the averaged contribution of eddies attached to the sea surface whose sizes are related to the surface geometry. This yields a coupling between long wind-waves and turbulence at heights of about 10 m. This new wind-and-waves coupling is thus not exclusively confined to the short wave range and heights below 5 m, where most of the momentum transfer to the waves is known to occur. The proposed framework clarifies the impact of wind-waves on Monin–Obukhov similarity theory, and the role of long wind-waves on the observed wind-wave variability of...
Tipo: Text Palavras-chave: Air-sea fluxes; Wall-bounded turbulence; Wave boundary layer; Wind stress; Wind-waves.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00601/71285/69691.pdf
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