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Registros recuperados: 67
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2D vortex interaction in a non-uniform flow ArchiMer
Perrot, Xavier; Carton, Xavier.
In a two-dimensional incompressible fluid, we study the interaction of two like-signed Rankine vortices embedded in a steady shear/strain flow. The numerical results of vortex evolutions are compared with the analytical results for point vortices. We show the existence of vortex equilibria, and of merger for initial distances larger than those without external flow. The evolutions depend on the initial orientation of the vortices in the external flow.
Tipo: Text Palavras-chave: Two-dimensional incompressible flows; Vortex merger; Pseudo-spectral model.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/2009/publication-7442.pdf
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A census of Meddies in a long-term high-resolution simulation ArchiMer
Barbosa Aguiar, Ana Claudia; Peliz, Alvaro; Carton, Xavier.
The output from a high-resolution two-decade long Mediterranean Outflow simulation is analysed here to provide a census of Mediterranean Water eddies (aka Meddies), both anticyclones and cyclones. The formation rate of Meddies that survive for at least 90 days is of 12 Meddies yr(-1) of which similar to 12% are cyclones. The rate of formation reaches 40 Meddies yr(-1) (30% cyclones) when considering all the Meddies living over 15 days. About 70% of the population is born along the southwestern Iberian slope, but several robust Meddles also originate in points of convergence of the main pathways into the open ocean. The longest-lived Meddies propagate northwestwards, but most of the anticyclones veer southwestwards after a while. As the Meddies drift away...
Tipo: Text
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00159/27073/25474.pdf
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A Conservative Model for Nonlinear Dynamics in a Stratified, Rotating Fluid ArchiMer
Filatoff, Nicolas; Carton, Xavier.
We present a set of equations describing the nonlinear dynamics of flows constrained by environmental rotation and stratification (Rossby numbers Ro∈[0.1,0.5] and Burger numbers of order unity). The fluid is assumed incompressible, adiabatic, inviscid and in hydrostatic balance. This set of equations is derived from the Navier Stokes equations (with the above properties), using a Rossby number expansion with second order truncation. The resulting model has the following properties: 1) it can represent motions with moderate Rossby numbers and a Burger number of order unity; 2) it filters inertia-gravity waves by assuming that the divergence of horizontal velocity remains small; 3) it is written in terms of a single function of space and time (pressure,...
Tipo: Text Palavras-chave: Incompressible and Stratified Fluids; Intermediate Model; Rossby Number; Burger Number; Conservation Properties; Energy; Potential Vorticity.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00600/71195/69561.pdf
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A model of the general circulation in the Persian Gulf and in the Strait of Hormuz: Intraseasonal to interannual variability ArchiMer
Pous, Stephane; Lazure, Pascal; Carton, Xavier.
Previous studies modeling the circulation and thermohaline structure in the Persian Gulf have suggested that interannual variability and vertical mixing processes could explain the model biases when compared to the few observations available. Here, a realistic, interannual, high-resolution model of the Persian Gulf is presented, validated against observations and then used to describe the intraseasonal to interannual variability in the circulation, water mass formation and exchange through the Strait of Hormuz. Sensitivity experiments to model settings, in particular vertical mixing parameterizations, have been performed in order to have the best comparison with all available observations. Main circulation and water mass characteristics correspond well to...
Tipo: Text Palavras-chave: Persian Gulf; Strait of Hormuz; Numerical model; Hydrology; Currents; Interannual variability.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00244/35563/35324.pdf
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A Process Study of the Tidal Circulation in the Persian Gulf ArchiMer
Pous, Stephane; Carton, Xavier; Lazure, Pascal.
A homogeneous shallow-water model with free surface is used to model the tidal circulation in the Persian Gulf. The numerical finite-difference model includes harmonic diffusion of horizontal momentum and quadratic bottom friction, it has a 9 km mesh size and it is forced by 7 tidal components at its southern boundary. High precision bathymetric data are used to obtain the bottom topography. The numerical model is run for more than a year. The results are the following: 1) The model accurately reproduces the tidal phase and amplitude observed at 42 tidal gauges in the region. This accuracy is attributed to the presence of the 7 components which are able to interact nonlinearly; 2) The amphidromic points are also well positioned by the model due to a proper...
Tipo: Text Palavras-chave: Persian Gulf; Barotropic Tide; Hydrodynamical Modeling; Comparison with Data.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00284/39520/38013.pdf
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A Process Study of the Wind-Induced Circulation in the Persian Gulf ArchiMer
Pous, Stephane; Carton, Xavier; Lazure, Pascal.
A shallow-water model, coupled with a three dimensional, hydrostatic ocean model, is used to study the wind induced circulation, and the Shatt-al-Arab river plume expansion, in the Persian Gulf. The models are used in an idealized configuration. The following results are obtained: 1) with northwesterly winds, a double gyre is formed: this gyre is cyclonic in the south and anticyclonic in the north. Southeastward currents flow along the Iranian and Arabian coast where the wind stress at the surface dominates the pressure gradient related to the free surface slope, and conversely in the deeper region of the Gulf; 2) In the eastern part of the Gulf, the cyclonic gyre intensifies, as observed and reported in the literature; 3) For northwesterly winds, the...
Tipo: Text Palavras-chave: Persian Gulf; Wind-Induced Circulation; Hydrodynamical Modeling.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00284/39521/38014.pdf
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A seasonal dipolar eddy near Ras Al Hamra (Sea of Oman) ArchiMer
L'Hegaret, Pierre; Lacour, Leo; Carton, Xavier; Roullet, Guillaume; Baraille, Remy; Correard, Stephanie.
Trajectories and hydrological data from two Argo floats indicate that warm and salty water at 200–300-m depths was ejected from the coast of Oman, near Ras al Hamra, in spring 2008, 2011, and 2012. This warm and salty water, Persian Gulf Water (PGW), once ejected from the coast, recirculated cyclonically in the western Sea of Oman, but also flowed eastward along the Iranian and Pakistani coasts. There, it was expelled seaward by mesoscale eddies as shown by other float data. Seasonal maps of salinity were computed from all available Argo floats; they showed that, in spring, PGW is present in the middle and north of the Sea of Oman, contrary to fall, when the salinity maxima lie southeast of Ras al Hadd. The ejection of PGW from Ras al Hamra is related here...
Tipo: Text Palavras-chave: Sea of Oman; Outflow; Eddies; Argo floats.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00171/28206/33894.pdf
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An index to distinguish surface and subsurface intensified vortices from surface observations ArchiMer
Assassi, Charefeddine; Morel, Y.; Vandermeirsch, Frederic; Chaigneau, A.; Pegliasco, C.; Morrow, R.; Colas, F.; Fleury, S.; Carton, Xavier; Klein, Patrice; Cambra, R..
In this study, we first show that it is difficult to reconstruct the vertical structure of vortices using only surface observations. In particular we show that the recent SQG and ISQG methods systematically lead to surface intensified vortices and those subsurface intensified vortices are thus not correctly modelled. We then investigate the possibility to distinguish between surface and subsurface intensified eddies from surface data only, using the sea surface height and the sea surface temperature available from satellite observations. A simple index, based on the ratio of the sea surface temperature anomaly and the sea level anomaly, is proposed. While the index is expected to give perfect results for isolated vortices, we show that in a complex...
Tipo: Text
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00343/45406/44921.pdf
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Arms winding around a meddy seen in seismic reflection data close to the Morocco coastline ArchiMer
Menesguen, Claire; Hua, Bach-lien; Carton, Xavier; Klingelhoefer, Frauke; Schnurle, Philippe; Reichert, C..
The North Atlantic temperature and salinity distributions are strongly influenced by the existence of Mediterranean eddies (meddies) which significantly contribute to the transport of the warm and salty Mediterranean Water along different pathways. The most common pathways are observed to be North and West of the Canary Current. However, a 2011 seismic reflection cruise conducted by BGR and Ifremer near the North-Western African margin of Morocco, MIRROR Leg 2, revealed the presence of a meddy south of the Azores front and very close to the Morocco coastline. This unusual location of a strong Mediterranean Water anomaly is confirmed by other data. Moreover, meddies are long-lived structures whose dynamics and dissipation are not yet completely understood....
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00074/18499/16046.pdf
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Baroclinic multipole formation from heton interaction ArchiMer
Sokolovskiy, Mikhail A.; Carton, Xavier.
In a two-layer quasi-geostrophic model, the interaction between two opposite-signed hetons (baroclinic vortex pairs) is studied analytically and numerically, for singular and finite-area vortices. For point vortices, using trilinear coordinates, it is shown that the possible evolutions depend on the deformation radius Rd: for large Rd, the layers decouple, vortices pair in each layer and their trajectories are open; for medium Rd, the exchange of opposite-sign partners between layers becomes possible; for small Rd, two other regimes appear: one where hetons remain unaltered during their evolution but follow open trajectories, and one where hetons occupy only a bounded subdomain of space at all times. Conditions for invariant co-rotation of the heton pair...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00002/11351/7924.pdf
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Campagne SEMANE 2002. Rapport de données CTD-O2 ArchiMer
Billant, Andre; Branellec, Pierre; Carton, Xavier.
The SEMANE experiments initiated by SHOM in 1995 have collected a large set of hydrological and current measurements aiming at characterizing the paths of Med water on the Iberian slope, as well as the variations of these paths. These variations include both eddy fluctuations induced by instability of the sub currents or by topography, and the longer term variations (at seasonal and interannual timescale). The 2002 experiment has renewed the 3 high-resolution CTD-LADCP (8.20W, 6.15W, 35.50N) in the gulf of Cadiz, to complement the previous realizations and to better assess the interannual variations (sections achieved at the same period of the year). The first analyses of previous experimental data both in stationary inverse modeling and for prognostic...
Tipo: Text
Ano: 2004 URL: http://archimer.ifremer.fr/doc/00210/32145/30602.pdf
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Characteristics of surface signatures of Mediterranean water eddies ArchiMer
Bashmachnikov, I.; Carton, Xavier; Belonenko, T. V..
In this work, we obtain new results on the manifestation of meddies (or of other deep eddies) at the sea-surface, further developing the results by Bashmachnikov and Carton (2012). The quasi-geostrophic equations are used to describe a near-axisymmetric vortex in the upper ocean, forced at its lower boundary by the isopycnal elevation of a moving meddy. The solution thus obtained provides a better approximation of the characteristics of meddy surface signals. The results show that in subtropics large meddies with dynamic radius R-m >30 km are always seen at the sea-surface with AVISO altimetry, that medium-size meddies with R-m = 20 km may be seen at the sea-surface only if they are sufficiently shallow and strong, while small meddies with R-m =10 km...
Tipo: Text Palavras-chave: Meddies; Surface signal; Altimetry.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00245/35615/34134.pdf
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Contrasting biogeochemical cycles of cobalt in the surface western Atlantic Ocean ArchiMer
Dulaquais, Gabriel; Boye, Marie; Middag, Rob; Owens, Stephanis; Puigcorbe, Viena; Buesseler, Ken; Masque, Pere; De Baar, Hein J. W.; Carton, Xavier.
Dissolved cobalt (DCo; <0.2 µm; 14 to 93 pM) and the apparent particulate cobalt (PCo; >0.2 µm; <1 to 15 pM) were determined in the upper water column (<1000 m) of the western Atlantic Ocean along the GEOTRACES-A02 section (64°N to 50°S). The lowest DCo concentrations, typical of a nutrient-type distribution were observed in surface waters of the subtropical domains. Strong linear relationships between DCo and phosphate (P) as well as meridional gradients of decreasing DCo from high latitudes were characterized and both linked to the Co biological requirement. External sources such as the Amazon and the atmospheric deposition were found to contribute significantly (>10%) to the DCo stock of the mixed layer in the equatorial and north...
Tipo: Text Palavras-chave: Cobalt; Biogeochemistry; Atlantic Ocean; Chemical Oceanography; GEOTRACES.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00241/35222/33732.pdf
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Cyclones and Anticyclones in Seismic Imaging ArchiMer
Barbosa Aguiar, A. C.; Menesguen, Claire; Le Gentil, Sylvie; Schopp, Richard; Carton, Xavier.
Nearly all the subsurface eddies detected in seismic imaging of sections in the northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MW cyclones have been observed and studied. In this study, the work of previous numerical studies is extended to investigate some characteristics of layering surrounding MW cyclones, using a primitive equation model with equal diffusivities for salinity and temperature to suppress the effects of double diffusion. It is shown that, after a stable state is reached, both anticyclones and cyclones display similar patterns of layering: stacked thin layers of high acoustic reflectivity located above and below the core of each vortex, which do not match isopycnals. The authors conclude...
Tipo: Text Palavras-chave: Geographic location/entity; North Atlantic Ocean; Circulation/ Dynamics; Small scale processes; Atm/Ocean Structure/ Phenomena; Eddies; Vortices; Observational techniques and algorithms; Acoustic measurements/effects; Models and modeling; Primitive equations model.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00281/39190/37746.pdf
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Deep lenses of circumpolar water in the Argentine Basin - art. no. 3007 ArchiMer
Arhan, Michel; Carton, Xavier; Piola, A; Zenk, W.
[1] Three deep anticyclonic eddies of a species only reported once before [Gordon and Greengrove, 1986] were intersected by hydrographic lines of the World Ocean Circulation Experiment (WOCE) and South Atlantic Ventilation Experiment (SAVE) programs in the Argentine Basin. The vortices are centered near 3500 m depth at the interface between North Atlantic Deep Water and Bottom Water. They have similar to1500-m-thick cores containing Lower Circumpolar Deep Water and a dynamical influence that may span up to two thirds of the water column. As one eddy was observed just downstream of the western termination of the Falkland Escarpment, a destabilization of the deep boundary current by the sudden slope relaxation is suggested as a potential cause of eddy...
Tipo: Text Palavras-chave: Eddies and mesoscale processes; Western boundary currents; Hydrography.
Ano: 2002 URL: https://archimer.ifremer.fr/doc/00000/10057/7797.pdf
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Eddy-topography interactions and the fate of the Persian Gulf Outflow ArchiMer
Vic, C.; Roullet, Guillaume; Capet, Xavier; Carton, Xavier; Molemaker, Maarten Jeroen; Gula, J..
The Persian Gulf feeds a warm and salty outflow in the Gulf of Oman (northern Arabian Sea). The salt climatological distribution is relatively smooth in the Gulf of Oman, and the signature of a slope current carrying salty waters is difficult to distinguish hundreds of kilometers past the Strait of Hormuz, in contrast to other outflows of the world ocean. This study focuses on the mechanisms involved in the spreading of Persian Gulf Water (PGW) in the Gulf of Oman, using a regional primitive equation numerical simulation. The authors show that the dispersion of PGW occurs through a regime that is distinct from, for example, the one responsible for the Mediterranean outflow dispersion. The background mesoscale eddy field is energetic and participates...
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Ano: 2015 URL: http://archimer.ifremer.fr/doc/00302/41332/40512.pdf
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Effects of Monsoon Winds and Topographical Features on the Vertical Thermohaline and Biogeochemical Structure in the Gulf of Tadjourah (Djibouti) ArchiMer
Omar, Youssouf Moussa; Memery, Laurent; Carton, Xavier; Daher, Abdourahman; Duvielbourg, Eric.
The vertical thermohaline and biogeochemical structures of the upper layer (0 - 200 m) were studied in the Gulf of Tadjourah using high-resolution hydrographic data collected in July-August 2013, September 2013 and February 2014. During summer, the superficial layer consisted of the mixed layer (ML) extending to a depth of about 20 - 30 m followed by the thermocline located between 30 and 50 m depth. The ML was thicker in the west and the southeast where the thermal gradient and chlorophyll a concentrations were particularly high. During September, this stratification persisted but the ML became warmer and saltier and the thermocline moved slightly deeper. In February, the ML extended to about 120 m, and the thermocline was less pronounced. A comparison of...
Tipo: Text Palavras-chave: Thermohaline; Biogeochemical Structures; Mixed Layer Depth; Thermocline; Monsoon Wind; Topography.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00601/71286/69693.pdf
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Evidence of Mediterranean Water dipole collision in the Gulf of Cadiz ArchiMer
L'Hegaret, Pierre; Carton, Xavier; Ambar, Isabel; Menesguen, Claire; Hua, Bach Lien; Cherubin, Laurent; Aguiar, Ana; Le Cann, Bernard; Daniault, Nathalie; Serra, Nuno.
A collision of Mediterranean Water dipoles in the Gulf of Cadiz is studied here, using data from the MedTop and Semane experiments. First, a Mediterranean Water eddy (meddy) was surveyed hydrologically in November 2000 southwest of Cape Saint Vincent. Then, this meddy drifted northeastward from this position, accompanied by a cyclone (detected only via altimetry), thus forming a first dipole. In February 2001, a dipole of Mediterranean Water was measured hydrologically just after its formation near Portimão Canyon. This second dipole drifted southwestward. The western and eastern meddies had hydrological radii of about 22 and 25 km, respectively, with corresponding temperature and salinity maxima of (13.45°C, 36.78) and (11.40°C, 36.40). Rafos float...
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00204/31565/29986.pdf
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Explosive instability of geostrophic vortices. Part 1: baroclinic instability ArchiMer
Carton, Xavier; Flierl, Glenn R.; Perrot, Xavier; Meunier, Thomas; Sokolovskiy, Mikhail.
In a quasi-geostrophic model, we study the baroclinic instability of a two-layer vortex. The singular unstable modes for potential vorticity anomalies are compared with the classical normal modes. Short-time singular modes are explosively unstable and, at short times, depend only on the baroclinic component of the flow. As time progresses, they evolve towards the normal modes and their sensitivity to flow parameters is explored. Asymptotic solutions are provided.
Tipo: Text Palavras-chave: Quasi-geostrophic equations; Inviscid flows; Vortex stability; Normal or singular modes; Parametric resonance.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00002/11352/7925.pdf
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Explosive instability of geostrophic vortices. Part 2: parametric instability ArchiMer
Carton, Xavier; Meunier, Thomas; Flierl, Glenn R.; Perrot, Xavier; Sokolovskiy, Mikhail.
In a two-layer quasi-geostrophic model, a baroclinic vortex is submitted to a periodic forcing of its mean baroclinic azimuthal velocity. It is shown that parametric effects could stabilize a vortex which is baroclinically unstable in the absence of forcing. Conversely, parametric resonance can destabilize a baroclinically stable vortex, under conditions on the vortex parameters, on the ratio of layer thicknesses or on the forcing frequency.
Tipo: Text Palavras-chave: Quasi-geostrophic equations; Inviscid flows; Vortex stability; Parametric resonance.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00002/11353/7926.pdf
Registros recuperados: 67
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