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| Registros recuperados: 211 | |
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| Mouche, Alexis; Chapron, Bertrand. |
| Using colocated ASCAT and ECMWF winds, a careful global analysis of ENVISAT and Sentinel-1 synthetic aperture radar (SAR) measurements helps to refine, at medium resolution (tens of kilometers) and especially for HH configuration, a C-band geophysical model function (GMF, i.e., C-SARMOD) to analyze wind sensitivity for different incidence and azimuth angles. Results unify major findings from previous global and case studies for polarization ratio (PR, VV/HH), polarization difference (PD, VV-HH), and cross-polarization (CP). At lower level than standard two-scale predictions, PR increases with increasing incidence angle and decreases with increasing wind speed. PR further exhibits a strong azimuthal modulation, with maximum values in downwind... |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00289/40022/38605.pdf |
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| Ardhuin, Fabrice; Collard, Fabrice; Chapron, Bertrand; Ardhuin, Fanny; Guitton, Gilles; Mouche, Alexis; Stopa, Justin. |
| Swell evolution from the open ocean into sea ice is poorly understood, in particular the amplitude attenuation expected from scattering and dissipation. New synthetic aperture radar (SAR) data from Sentinel-1A wave mode reveal intriguing patterns of bright oscillating lines shaped like instant noodles. We investigate cases in which the oscillations are in the azimuth direction, around a straight line in the range direction. This observation is interpreted as the distortion by the SAR processing of crests from a first swell, due to the presence of a second swell. Since deviations from a straight line should be proportional to the orbital velocity toward the satellite, swell height can be estimated, from 1.5 to 5 m in the present case. The evolution of this... |
| Tipo: Text |
Palavras-chave: Ocean waves; SAR; Sea ice. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00256/36718/35332.pdf |
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| De Farias, Eduardo G. G.; Lorenzzetti, Joao A.; Bentamy, Abderrahim; Chapron, Bertrand; Romain, Husson. |
| Recently, with the availability of a great number of synthetic aperture radar (SAR) wave mode spectra, it has been possible to derive a set of great circle lines of swell propagation whose intersection points indicate the position of the storm generating the observed swell field. However, due to the inherent limitations of SAR spectra, the locus of convergence of great circle of swell propagation can be sometimes diffuse or contain multiple convergence regions. In this letter, we adapted the fuzzy cluster logic method to identify the regions of convergence of SAR wave field rays. The analysis of the results of the fuzzy algorithm clearly indicates the ability of this statistical method to identify the cluster center region of swell fields observed in SAR... |
| Tipo: Text |
Palavras-chave: Swell wave fields and fuzzy logic; Synthetic aperture radar (SAR). |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00109/21992/20637.pdf |
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| Bauer, Werner; Chandramouli, Pranav; Chapron, Bertrand; Li, Long; Mémin, Etienne. |
| An important open question in fluid dynamics concerns the effect of smallscales in structuring a fluid flow. In oceanic or atmospheric flows, this is aptly captured in wave-current interactions through the study of the wellknown Langmuir secondary circulation. Such wave-current interactions are described by the Craik-Leibovich system, in which the action of a wave induced velocity, the Stokes drift, produces a so called “vortex force” that causes streaking in the flow. In this work, we show that these results can be generalized as a generic effect of the spatial inhomogeneity of the statistical properties of the small-scale flow components. As demonstrated, this is well captured through a stochastic representation of the flow. |
| Tipo: Text |
Palavras-chave: Langmuir circulation; Baroclinic models; General circulation models; Stochastic models; Oscillations. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00610/72194/70975.pdf |
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| 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... |
| Tipo: Text |
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| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00000/11094/7418.pdf |
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| Ardhuin, Fabrice; Gille, Sarah T.; Menemenlis, Dimitris; Rocha, Cesar B.; Rascle, Nicolas; Chapron, Bertrand; Gula, Jonathan; Molemaker, Jeroen. |
| Tidal currents and large-scale oceanic currents are known to modify ocean wave properties, causing extreme sea states that are a hazard to navigation. Recent advances in the understanding and modeling capability of open ocean currents have revealed the ubiquitous presence of eddies, fronts and filaments at scales 10 to 100∼km. Based on realistic numerical models, we show that these structures can be the main source of variability in significant wave heights at scales less than 200 km, including important variations down to 10 km. Model results are consistent with wave height variations along satellite altimeter tracks, resolved at scales larger than 50 km. The spectrum of significant wave heights is found to be of the order of 70〈Hs〉2/(g2〈Tm0,-1〉2) times... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00382/49328/49708.pdf |
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| Cheng, Yongcun; Tournadre, Jean; Li, Xiaofeng; Xu, Qing; Chapron, Bertrand. |
| Ocean surface films can damp short capillary-gravity waves, reduce the surface mean square slope, and induce “sigma0 blooms” in satellite altimeter data. No study has ascertained the effect of such film on altimeter measurements due to lack of film data. The availability of Environmental Response Management Application (ERMA) oil cover, daily oil spill extent and thickness data acquired during the Deepwater Horizon (DWH) oil spill accident provides a unique opportunity to evaluate the impact of surface film on altimeter data. In this study, the Jason-1/2 passes nearest to the DWH platform are analyzed to understand the waveform distortion caused by the spill as well as the variation of σ0 as a function of oil thickness, wind speed and radar band. Jason-1/2... |
| Tipo: Text |
Palavras-chave: Oil spill; Altimeter; Sigma0 bloom; Waveform. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00381/49203/49635.pdf |
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| Carlier, Antoine; Chauvaud, Laurent; Van Der Geest, Matthijs; Le Loc'H, Francois; Le Duff, Michel; Vernet, Marc; Raffray, Jean; Diakhate, Djibril; Labrosse, Pierre; Wague, Abdoulaye; Le Goff, Clement; Gohin, Francis; Chapron, Bertrand; Clavier, Jacques. |
| Banc d’Arguin (BA), Mauritania, is a nationally protected shallow gulf > 10,000 km2 between the Sahara desert and the upwelling system off the Mauritanian coast. In the southeast, BA consists of a 500 km2 tidal flat, the most important wintering site for shorebirds using the East Atlantic Flyway. The Mauritanian upwelling-driven phytoplankton production supports the most productive fisheries worldwide, but little is known about its trophic role in the functioning of the inshore BA food web. Using stable isotopes as trophic tracers to distinguish between upwelling-driven phytoplankton, open ocean phytoplankton, and benthic primary producers, we assessed the spatial extent to which the inshore BA food web is fuelled by upwelling-driven phytoplankton... |
| Tipo: Text |
Palavras-chave: Banc d'Arguin; West Africa; Food web structure; Remote sensing; Stable isotope; Upwelling. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00269/37999/36078.pdf |
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| Kozlov, Igor; Romanenkov, Dmitry; Zimin, Alexei; Chapron, Bertrand. |
| The compiled archive of synthetic aperture radar (SAR) images acquired by the Advanced SAR (ASAR) onboard the Envisat satellite over the White Sea during the extended summer periods (May-September) between 2007 and 2011, provides the first detailed analysis of 2-D patterns of internal waves (IWs) in the White Sea. Unambiguously, the primary region of IW activity is the southwestern (SW) Gorlo Strait (GS). LW packets emerging from this area are regularly observed to reach crest lengths up to 200 km, and also to propagate a few hundred kilometers from their origin. Model results confirm that large-scale IWs can be generated every tidal cycle and are able to cross the entire sea. As suggested, the source of these packets is governed by the intense dynamics of... |
| Tipo: Text |
Palavras-chave: SAR imaging; Nonlinear internal waves; The White Sea; Vertical mixing. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00195/30617/29216.pdf |
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| Tran, Ngan; Chapron, Bertrand. |
| The authors report the first results in studying the polarization anisotropy of the microwave backscatter from nadir observations provided by Jason-1 altimeter in both Ku- and C-band. A small but clear wind direction signal for wind speeds above 6 m/s is revealed. These azimuthal variations of radar cross-section increase with increasing wind speed up to 14 m/s. The signatures then level off at higher winds. These results extend, for the first time, recent theoretical improved scattering approximation, and point some similarities between scattering and emission mechanisms at nadir. The observed directional effect can thus be interpreted as a signature of the curvature anisotropy of wind-generated short-scale waves. Sensitivities to both wind speed and sea... |
| Tipo: Text |
Palavras-chave: Altimeter; Radar cross section; Polarization; Wind direction; Sea state. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00004/11557/8150.pdf |
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| Le Caillec, Jm; Garello, R; Chapron, Bertrand. |
| In this paper, the synthetic aperture radar (SAR) process of the ocean surface mapping is studied using a decomposition based on a Volterra model. By a mathematical expansion of the complex exponential of the complete SAR transform, these models decompose the nonlinear distortion mechanisms of the SAR spectrum over different spectra of polynomial interactions. Thus, they offer an alternative modeling (to the exact SAR transform) giving a theoretical separation between the SAR Fourier components linearly derived from the sea surface elevation and the artifacts created by nonlinearities of. the SAR mapping of the. ocean surface. The main results of this paper consist of the systematic assessment of such an approximation of the ocean surface SAR imaging... |
| Tipo: Text |
Palavras-chave: Higher order statistics; Radar mapping; SAR; Sea surface; Volterra models. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00000/10606/9500.pdf |
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| Rascle, Nicolas; Chapron, Bertrand; Molemaker, Jeroen; Nouguier, Frederic; Ocampo‐torres, Francisco J.; Osuna Cañedo, J. Pedro; Marié, Louis; Lund, Björn; Horstmann, Jochen. |
| Sea surface roughness is affected by surface current gradients, which provides a means of monitoring from satellite sharp oceanic fronts. This paper is the second report of an experiment designed to compare observations of sea surface roughness and surface currents at an unprecedented accuracy, owing to the conjunction of numerous deployed drifters and roughness instruments. About 200 drifters sampled a thin 10~km elongated submesoscale front, also monitored by a high density of roughness instruments: satellite Synthetic Aperture Radar, satellite and airborne multi‐angle sunglint radiometers. The first paper focused on the retrieval of the current gradient direction (convergence and cyclonic vorticity) at the front, using roughness observations at multiple... |
| Tipo: Text |
Palavras-chave: Sea surface roughness; Submesoscale current; Fine-scale current; Synthetic aperture radar (SAR); Sunglint Sun glitter; Ocean front. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00636/74788/75035.pdf |
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| 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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| Yurovsky, Yu. Yu.; Kudryavtsev, V. N.; Grodsky, S. A.; Chapron, Bertrand. |
| Field data taken from the Black Sea Research platform during 2009-2015 are used to develop a dual-co-polarized (VV and HH) empirical model for the sea surface normalized radar cross-section (NRCS) and Doppler Velocity (DV) in the Ka-band. A fitting function for the NRCS is the standard truncated Fourier series in azimuth with polynomial coefficients dependent on incidence angle and wind speed. The data are corrected for the angular antenna pattern, which is measured in special calibration procedures. The resulting NRCS model is consistent with other rare Ka-band measurements and agrees well with Ku-band geophysical model functions, in contrast with previously proposed Ka-band models. Surface is subtracted from measured DV using either propeller current... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00437/54829/56288.pdf |
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| Kudryavtsev, Vladimir N.; Chapron, Bertrand; Myasoedov, Alexander G.; Collard, Fabrice; Johannessen, Johnny A.. |
| An effective methodology using satellite high-resolution polarized information to interpret and quantitatively assess various surface ocean phenomena is suggested. Using a sample RADARSAT-2 quad-polarization ocean synthetic aperture radar (SAR) scene, the dual co-polarization (VV and HH) radar data are combined into polarization difference, polarization ratio, and nonpolarized components. As demonstrated, these field quantities provide means to distinguish Bragg scattering mechanism and radar returns from breaking waves. As shown, quantitative characteristics of the surface manifestation of ocean currents, slicks, and wind field features in these dual co-polarization properties are very different and may be effectively used in the development of new SAR... |
| Tipo: Text |
Palavras-chave: Radar cross sections; Radar signal analysis; Synthetic aperture radar (SAR) imaging. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00149/26042/24890.pdf |
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| Van Sebille, Erik; Aliani, Stefano; Law, Kara Lavender; Maximenko, Nikolai; Alsina, José M; Bagaev, Andrei; Bergmann, Melanie; Chapron, Bertrand; Chubarenko, Irina; Cózar, Andrés; Delandmeter, Philippe; Egger, Matthias; Fox-kemper, Baylor; Garaba, Shungudzemwoyo P; Goddijn-murphy, Lonneke; Hardesty, Britta Denise; Hoffman, Matthew J; Isobe, Atsuhiko; Jongedijk, Cleo E; Kaandorp, Mikael L A; Khatmullina, Liliya; Koelmans, Albert A; Kukulka, Tobias; Laufkötter, Charlotte; Lebreton, Laurent; Lobelle, Delphine; Maes, Christophe; Martinez-vicente, Victor; Morales Maqueda, Miguel Angel; Poulain-zarcos, Marie; Rodríguez, Ernesto; Ryan, Peter G; Shanks, Alan L; Shim, Won Joon; Suaria, Giuseppe; Thiel, Martin; Van Den Bremer, Ton S; Wichmann, David. |
| Marine plastic debris floating on the ocean surface is a major environmental problem. However, its distribution in the ocean is poorly mapped, and most of the plastic waste estimated to have entered the ocean from land is unaccounted for. Better understanding of how plastic debris is transported from coastal and marine sources is crucial to quantify and close the global inventory of marine plastics, which in turn represents critical information for mitigation or policy strategies. At the same time, plastic is a unique tracer that provides an opportunity to learn more about the physics and dynamics of our ocean across multiple scales, from the Ekman convergence in basin-scale gyres to individual waves in the surfzone. In this review, we comprehensively... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00610/72213/71011.pdf |
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| Drinkwater, Mark; Rebhan, Helge; Le Traon, Pierre-yves; Phalippou, Laurent; Cotton, David; Johannessen, Johnny; Ruffini, Giulio; Bahurel, Pierre; Bell, Mike; Chapron, Bertrand; Pinardi, Nadia; Robinson, Ian; Santoleri, Lia; Stammer, Detlef. |
| Oceans cover approximately 70% of the Earth's surface and, with about 60% of the World's population living within 200 km of the coast, they have an untold impact on all of us. Not surprisingly, for people living close to the coast or those who depend on the ocean for their livelihood, regular forecasts of ocean conditions are just as important as traditional weather forecasts. Therefore, development of the infrastructure needed to support and sustain independent, European operational ocean forecasting, and the associated coastal and marine information services, are key priorities of the joint Global Monitoring for Environment and Security (GMES) initiative by the European Commission and ESA. |
| Tipo: Text |
Palavras-chave: Meteorology; Infrastructure; Maturation; World's oceans. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-903.pdf |
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| Zabolotskikh, Elizaveta V.; Mitnik, Leonid M.; Chapron, Bertrand. |
| A methodology, based on model simulations and neural networks inversion, is proposed to jointly retrieve sea surface wind speed, sea surface temperature, atmospheric water vapor content, cloud liquid water content, and total atmospheric absorption at 10.65GHz using Advanced Microwave Scanning Radiometer 2 measurements. In particular, estimation of the total atmospheric absorption at 10.65GHz, which can be done with high accuracy due to the not so strong influence of liquid water and especially water vapor, helps to refine a new filter to considerably reduce masking ocean areas for severe weather systems, characterized by high wind speeds and moderate atmospheric absorption, appropriate for studying winter extratropical cyclone and polar low systems. A... |
| Tipo: Text |
Palavras-chave: Satellite passive microwave; Weather filter; High winds; AMSR-2; Atmospheric absorption. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00166/27752/25943.pdf |
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| Registros recuperados: 211 | |
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