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Registros recuperados: 10
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SKIM, a Candidate Satellite Mission Exploring Global Ocean Currents and Waves ArchiMer
Ardhuin, Fabrice; Brandt, Peter; Gaultier, Lucile; Donlon, Craig; Battaglia, Alessandro; Boy, François; Casal, Tania; Chapron, Bertrand; Collard, Fabrice; Cravatte, Sophie; Delouis, Jean Marc; De Witte, Erik; Dibarboure, Gerald; Engen, Geir; Johnsen, Harald; Lique, Camille; Lopez-dekker, Paco; Maes, Christophe; Martin, Adrien; Marié, Louis; Menemenlis, Dimitris; Nouguier, Frederic; Peureux, Charles; Rampal, Pierre; Ressler, Gerhard; Rio, Marie-helene; Rommen, Bjorn; Shutler, Jamie D.; Suess, Martin; Tsamados, Michel; Ubelmann, Clement; Van Sebille, Erik; Van Den Oever, Martin; Stammer, Detlef.
The Sea surface KInematics Multiscale monitoring (SKIM) satellite mission is designed to explore ocean surface current and waves. This includes tropical currents, notably the poorly known patterns of divergence and their impact on the ocean heat budget, and monitoring of the emerging Arctic up to 82.5°N. SKIM will also make unprecedented direct measurements of strong currents, from boundary currents to the Antarctic circumpolar current, and their interaction with ocean waves with expected impacts on air-sea fluxes and extreme waves. For the first time, SKIM will directly measure the ocean surface current vector from space. The main instrument on SKIM is a Ka-band conically scanning, multi-beam Doppler radar altimeter/wave scatterometer that includes a...
Tipo: Text Palavras-chave: Ocean current; Tropics; Arctic; Doppler; Altimetry; Sea state; Remote sensing; Ocean waves.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00498/60964/64372.pdf
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Large-Scale Forces Under Surface Gravity Waves at a Wavy Bottom: A Mechanism for the Generation of Primary Microseisms ArchiMer
Ardhuin, Fabrice.
Primary microseisms are background seismic oscillations recorded everywhere on Earth with typical frequencies 0.05 < f < 0.1 Hz. They appear to be generated by ocean waves of the same frequency f, propagating over shallow bottom topography. Previous quantitative models for the generation of primary microseisms considered wave propagation over topographic features with either large scales, equivalent to a vertical point force, or small scales matching ocean wave wavelengths, equivalent to a horizontal force. While the first requires unrealistic bottom slopes to explain measured Rayleigh wave amplitudes, the second produced Love waves and not enough Rayleigh waves. Here we show how the small scales actually produce comparable horizontal and vertical...
Tipo: Text Palavras-chave: Microseisms; Ocean waves; Topography; Sand waves.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00461/57240/59237.pdf
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Estimates of ocean wave heights and attenuation in sea ice using the SAR wave mode on Sentinel-1A ArchiMer
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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Surfaces de mer et dissipation d'énergie ArchiMer
Veras Guimaraes, Pedro.
Stochastic wave formulations and models are the most common tools for the assessment and forecast of sea surface conditions. Their ability to account for some of the processes encountered by waves during their evolution remains however a central question. Among other processes, the wave dissipation is for instance still poorly quantified and traditional methods for wave measurements fail to proper insight into its physics in a wide range of conditions. In this context, the work presented in this PhD aims to explore available observation techniques for their application to several quantitative aspects of the dissipation of wave energy, and particularly for short wave modulated by strong tidal currents, for short wave modulated by longer waves. This work...
Tipo: Text Palavras-chave: Vagues; Stéréo-vidéo; Bouée dérivante; Modélisation; Interaction vague-courant; Modulation; Déferlement; Breaking; Ocean waves; Stereo video; Drifting buoy; Wave modeling; Wave-current interaction.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00498/60967/64375.pdf
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Measuring ocean waves in sea ice using SAR imagery: A quasi-deterministic approach evaluated with Sentinel-1 and in situ data ArchiMer
Ardhuin, Fabrice; Stopa, Justin; Chapron, Bertrand; Collard, Fabrice; Smith, Madison; Thomson, Jim; Doble, Martin; Blomquist, Byron; Persson, Ola; Collins, Clarence O., Iii; Wadhams, Peter.
Measurements of wave heights in marginal ice zones are limited to very few in situ data. Here we revisit the linear and quasilinear theories of Synthetic Aperture Radar imaging of waves in the particular case of waves in sea ice. Instead of only working with spectra, we have developed an iterative nonlinear algorithm to estimate phase-resolved deterministic maps of wave-induced orbital velocities, from which elevation spectra can be derived. Application of this algorithm to Sentinel 1A wave mode images in the Southern Ocean shows that it produces reasonable results for swells in all directions except when they propagate at a few degrees off the range direction. The estimate of wave parameters is expected to work best when the shortest wave components,...
Tipo: Text Palavras-chave: SAR; Sentinel-1A; Ocean waves; Sea ice.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00361/47214/47451.pdf
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Observations globales des vents et des vagues de surface de l'océan à l'aide de mesures de radars à synthèse d'ouverture spatiaux ArchiMer
Huimin, Li.
Spaceborne synthetic aperture radar (SAR) has been demonstrated invaluable in observing the global ocean winds and waves. SAR images acquired by multiple sensors are employed, including Sentinel-1(S-1), Envisat/ASAR, Gaofen-3 and Radarsat-2. This thesis reviews the commonly used SAR parameters (NRCS and azimuth cutoff) in the first part. A series of calibration steps are required to obtain a proper NRCS and assessment of NRCS is carried out for S-1wave mode (WV). It turns out that WV is poorly calibrated and is thus re-calibrated to obtain accurate NRCS. Azimuth cut off is demonstrated to be complementary to NRCS and can account for the sea state impact on the wind retrieval. Based on the available fully polarimetric SAR products, azimuth cut off is found...
Tipo: Text Palavras-chave: Radar à synthèse d'ouverture; Vents et vagues océaniques; Synthetic aperture radar; Ocean winds; Ocean waves.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00504/61575/65505.pdf
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Rogue Waves 2008 : Proceedings of a Workshop organized by Ifremer and held in Brest, France 13-14-15 October 2008 within the Brest Sea Tech Week 2008 ArchiMer
Olagnon, Michel; Prevosto, Marc.
Since the Rogue Waves 2000 and 2004 workshops, researchers have pursued activity in the proposition of models and descriptions that can improve our understanding of rogue waves. The Brest Rogue Waves 2008 workshop gathered again many scientists and engineers to an opportunity to confront and discuss their views on the subject. It provided an assessment of the State of the Art of research on those matters, and was one more step forward towards efficient mitigation measures.
Tipo: Text Palavras-chave: Face au risque de ces événements. Mots-clés : vagues; Extrêmes; Vagues anormales; Vagues scélérates; Ocean waves; Extremes; Rogue waves; Freak waves.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00133/24444/22459.pdf
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Extraction of coastal ocean wave fields from SAR images ArchiMer
Collard, Fabrice; Ardhuin, Fabrice; Chapron, Bertrand.
Wave spectra derived from synthetic aperture radar (SAR) images acquired by ENVISATs are compared to in situ measurements by seven sensors, deployed in a field experiment carried out on the French coast of La Manche (English Channel). The wave spectra inversion scheme is adapted for shallow water from the European Space Agency (ESA)'s operational processing techniques used for level 2 ocean wave products. Under the low to moderate wind speed observed conditions, overall good agreement is found between in situ and SAR observations over a wide range of wave heights and directions, including waves propagating in the radar azimuth direction and incidence angles different from the standard imagette products.
Tipo: Text Palavras-chave: Synthetic aperture radar; Ocean waves.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-1109.pdf
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Ocean waves across the Arctic: attenuation due to dissipation dominates over scattering for periods longer than 19 s ArchiMer
Ardhuin, Fabrice; Sutherland, Peter; Doble, Martin; Wadhams, Peter.
The poorly understood attenuation of surface waves in sea ice is generally attributed to the combination of scattering and dissipation. Scattering and dissipation have very different effects on the directional and temporal distribution of wave energy, making it possible to better understand their relative importance by analysis of swell directional spreading and arrival times. Here we compare results of a spectral wave model – using adjustable scattering and dissipation attenuation formulations – with wave measurements far inside the ice pack. In this case, scattering plays a negligible role in the attenuation of long swells. Specifically, scattering-dominated attenuation would produce directional wave spectra much broader than the ones recorded, and swell...
Tipo: Text Palavras-chave: Ocean waves; Sea ice; Tara; DAMOCLES.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00333/44455/44127.pdf
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The Effect of Water-Column Resonance on the Spectra of Secondary Microseism P-waves ArchiMer
Meschede, Matthias; Stutzmann, Eleonore; Farra, Veronique; Schimmel, Martin; Ardhuin, Fabrice.
We compile and analyze a dataset of secondary microseismic P-wave spectra that were observed by North American seismic arrays. Two distinct frequency bands, 0.13–0.15Hz and 0.19–0.21Hz, with enhanced P-wave energy characterize the dataset. Cluster analysis allows to classify the spectra and to associate typical spectral shapes with geographical regions: Low frequency dominated spectra (0.13-0.15Hz) are mostly detected in shallower regions of the North Atlantic and the South Pacific, as well as along the Central and South American Pacific coast. High frequency dominated spectra (0.19-0.21Hz) are mostly detected in deeper regions of the North-Western Pacific and the South Pacific. For a selected subset of high quality sources, we compute synthetic spectra...
Tipo: Text Palavras-chave: Secondary microseisms; Body waves; Noise source spectra; Ocean waves; Site effect.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00404/51517/52109.pdf
Registros recuperados: 10
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