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| Johannessen, J; Chapron, Bertrand; Collard, F; Kudryavtsev, V; Mouche, Alexis; Akimov, D; Dagestad, K. |
| Previous analysis of Advanced Synthetic Aperture Radar (ASAR) signals collected by ESA's Envisat has demonstrated a very valuable source of high-resolution information, namely, the line-of-sight velocity of the moving ocean surface. This velocity is estimated from a Doppler frequency shift, consistently extracted within the ASAR scenes. The Doppler shift results from the combined action of near surface wind on shorter waves, longer wave motion, wave breaking and surface current. Both kinematic and dynamic properties of the moving ocean surface roughness can therefore be derived from the ASAR observations. The observations are compared to simulations using a radar imaging model extended to include a Doppler shift module. The results are promising.... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-5168.pdf |
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| Kudryavtsev, V; Akimov, D; Johannessen, Johnny; Chapron, Bertrand. |
| [1] A new radar imaging model of ocean current features is proposed. The simulated normalized radar cross section ( NRCS) takes into account scattering from "regular'' surfaces ( by means of resonant Bragg scattering and specular reflections) and scattering from breaking waves. The description of background wind waves and their transformation in nonuniform medium is based on solution of the wave action conservation equation. Wave breaking plays a key role in the radar imaging model. Breaking waves scatter radio waves ( thus directly contributing to the NRCS), provide energy dissipation in wind waves ( thus defining the wave spectrum of intermediate scale waves), and generate short surface waves ( thus affecting Bragg scattering). Surface current,... |
| Tipo: Text |
Palavras-chave: Breaking waves; Scattering; Radar imaging model; Ocean surface current. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-762.pdf |
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| Johannessen, J; Kudryavtsev, V; Akimov, D; Eldevik, T; Winther, N; Chapron, Bertrand. |
| [1] The surface signatures of meandering fronts and eddies have been regularly observed and documented in synthetic aperture radar (SAR) images. Wave-current interactions, the suppression of short wind waves by natural film, and the varying wind field resulting from atmospheric boundary layer changes across an oceanic temperature front all contribute to the radar image manifestation of such mesoscale features. The corresponding imaging mechanisms are quantitatively explored using a new radar imaging model (Kudryavtsev et al., 2005) that solves the energy balance equation where wind forcing, viscous and wave breaking dissipation, wave-wave interactions, and generation of short waves by breaking waves are taken into account. High-quality and synoptic in situ... |
| Tipo: Text |
Palavras-chave: Mesoscale feature detection; Imaging radar model. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-1352.pdf |
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