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Quad-polarization SAR features of ocean currents ArchiMer
Kudryavtsev, Vladimir; Kozlov, I.; Chapron, Bertrand; Johannessen, J. A..
A methodology is demonstrated to exploit the polarization sensitivity of high-resolution radar measurements to interpret and quantify upper ocean dynamics. This study particularly illustrates the potential of quad-polarization synthetic aperture radar (SAR) measurements. The analysis relies on essential characteristics of the electromagnetic scattering mechanisms and hydrodynamical principles. As the relaxation scale of centimeter-scale ocean surface scatters is typically small, radar signal anomalies associated with surface manifestations of the upper ocean dynamics on spatial scales exceeding 100 m are mostly dominated by nonresonant and nonpolarized scatters. These “scalar” contributions can thus efficiently trace local breaking and near-breaking areas,...
Tipo: Text Palavras-chave: Quad-polarized SAR; SAR imaging of ocean current; Radar scattering; Wave-current interaction; Wave breaking.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00210/32152/30611.pdf
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Monitoring the surface inflow of Atlantic Water to the Norwegian Sea using Envisat ASAR ArchiMer
Hansen, M. W.; Johannessen, J. A.; Dagestad, K. F.; Collard, Fabrice; Chapron, Bertrand.
Sea surface range Doppler velocities from nearly 1200 Envisat Advanced Synthetic Aperture Radar (ASAR) acquisitions between 2007 and 2011, covering the Norwegian Sea, the North Sea, and the Skagerrak Sea, have been examined. After systematic corrections, the inflow of Atlantic Water to the Norwegian Sea, via the two branches of the Norwegian Atlantic Current, is investigated. Distinct expressions of the eastern branch, the Norwegian Atlantic Slope Current, are revealed with a speed of 20-40 cm/s and a clear manifestation of topographic steering along the 500 m isobath. The western branch, the Norwegian Atlantic Front Current, is also depicted but with lower surface velocities. Moreover, parts of the Norwegian Coastal Current are also detected with...
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00056/16771/14216.pdf
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Review and assessment of latent and sensible heat flux accuracy over the global oceans ArchiMer
Bentamy, Abderrahim; Piolle, Jean-francois; Grouazel, Antoine; Danielson, R.; Gulev, S.; Paul, Frederic; Azelmat, Hamza; Mathieu, P. P.; Von Schuckmann, Karina; Sathyendranath, S.; Evers-king, H.; Esau, I.; Johannessen, J. A.; Clayson, C. A.; Pinker, R. T.; Grodsky, S. A.; Bourassa, M.; Smith, S. R.; Haines, K.; Valdivieso, M.; Merchant, C. J.; Chapron, Bertrand; Anderson, A.; Hollmann, R.; Josey, S. A..
For over a decade, several research groups have been developing air-sea heat flux information over the global ocean, including latent (LHF) and sensible (SHF) heat fluxes over the global ocean. This paper aims to provide new insight into the quality and error characteristics of turbulent heat flux estimates at various spatial and temporal scales (from daily upwards). The study is performed within the European Space Agency (ESA) Ocean Heat Flux (OHF) project. One of the main objectives of the OHF project is to meet the recommendations and requirements expressed by various international programs such as the World Research Climate Program (WCRP) and Climate and Ocean Variability, Predictability, and Change (CLIVAR), recognizing the need for better...
Tipo: Text Palavras-chave: Ocean Heat Flux; Latent heat flux; Sensible heat flux; Ocean heat content; Scatterometer; Surface wind; Specfic air humidity; OceanSites; Remotely sensed data.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00403/51403/53729.pdf
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Mapping the Agulhas Current from space: An assessment of ASAR surface current velocities ArchiMer
Rouault, M. J.; Mouche, Alexis; Collard, Fabrice; Johannessen, J. A.; Chapron, Bertrand.
Over 2 years of surface current information collected in the Agulhas Current region and derived from the Doppler centroid anomalies of Envisat's advanced synthetic aperture radar (ASAR) are examined. The sources of errors and potential use of ASAR surface current velocities for oceanographic research are assessed. ASAR surface current velocities are compared to surface drifter data and merged altimetry observations. Maps of sea surface temperature are used to establish the ASAR's capacity to capture the synoptic circulation. Discrepancies between observed and predicted ASAR velocities result predominantly from inadequate wind corrections combined with radar incidence angles below 30 degrees. Occasionally observed wind-induced outliers cause a bias in the...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00016/12712/9639.pdf
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Use of satellite observations for operational oceanography: recent achievements and future prospects ArchiMer
Le Traon, Pierre-yves; Antoine, D.; Bentamy, Abderrahim; Bonekamp, H.; Breivik, L. A.; Chapron, Bertrand; Corlett, G.; Dibarboure, G.; Digiacomo, P.; Donlon, C.; Faugere, Y.; Font, J.; Girard-ardhuin, Fanny; Gohin, Francis; Johannessen, J. A.; Kamachi, M.; Lagerloef, G.; Lambin, J.; Larnicol, Gilles; Le Borgne, P.; Leuliette, E.; Lindstrom, E.; Martin, M. J.; Maturi, E.; Miller, L.; Mingsen, L.; Morrow, R.; Reul, Nicolas; Rio, Myriam; Roquet, H.; Santoleri, R.; Wilkin, J..
The paper gives an overview of the development of satellite oceanography over the past five years focusing on the most relevant issues for operational oceanography. Satellites provide key essential variables to constrain ocean models and/or serve downstream applications. New and improved satellite data sets have been developed and have directly improved the quality of operational products. The status of the satellite constellation for the last five years was, however, not optimal. Review of future missions shows clear progress and new research and development missions with a potentially large impact for operational oceanography should be demonstrated. Improvement of data assimilation techniques and developing synergetic use of high resolution satellite...
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Ano: 2015 URL: http://archimer.ifremer.fr/doc/00270/38094/36245.pdf
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Simulation of radar backscatter and Doppler shifts of wave-current interaction in the presence of strong tidal current ArchiMer
Hansen, M. W.; Kudryavtsev, V.; Chapron, Bertrand; Johannessen, J. A.; Collard, Fabrice; Dagestad, K. -f.; Mouche, A.a..
A radar imaging model including a Doppler shift module is presented for quantitative studies of radar observations of wave-current interaction in a strong tidal current regime. The model partitions the Doppler shift into the relative contribution arising from the motion of the backscattering facets including Bragg waves, specular points, and breaking waves that are advected by and interact with the underlying surface current. Simulated and observed normalized radar cross sections and Doppler shifts for different environmental conditions and radar parameters are compared and discussed. (C) 2012 Elsevier Inc. All rights reserved.
Tipo: Text Palavras-chave: SAR; Tidal current; Waves; Normalized radar cross section; Doppler velocity.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00083/19438/17086.pdf
Registros recuperados: 6
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