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| Registros recuperados: 20 | |
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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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| Nouguier, Frederic; Guerin, Charles-antoine; Soriano, Gabriel. |
| This paper is the first in a series of two papers on the use of combined improved hydrodynamic and electromagnetic analytical models for the simulation of the ocean Doppler spectrum at microwave frequencies. Under a linear assumption for the sea surface, we derive statistical expression for the main Doppler characteristics according to asymptotic scattering models. We consider classical models such as the Kirchhoff approximation and the two-scale model, as well as the more recent weighted curvature approximation (WCA). We recover two salient features of Doppler signature in the microwave regime. First, the Doppler characteristics are very sensitive to polarization, with higher mean Doppler shift in horizontal polarization. This is correctly rendered by the... |
| Tipo: Text |
Palavras-chave: Doppler spectrum; Gravity waves; Microwave; Remote sensing; Rough surfaces; Scattering; Sea surface. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00054/16524/14379.pdf |
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| Dioh, B.; Ndiaye, O.; Sané, K.; Diouf, P.S.. |
| Dans le programme de conservation des écosystèmes marins et côtiers de I'Akique de I'Ouest du World Wide Fund for Nature (WWF), Kayar a été retenu comme site où des activités de terrain doivent être menées. Dans le but de former et de sensibiliser les acteurs chargés de I'application des lois et règlements relatifs à la pêche et ceux à qui cette réglementation s'applique, une séance de vulgarisation des lois et règlements régissant la pêche au Sénégal a été organisée le 26 juillet 2002 à Kayar. Aprés la cérémonie d'ouverture, Messieurs Ousmane NDIAYE, Chef de la division pêche artisanale à la Direction de l'océanographie et des pêches maritimes (DOPM) et Alassane Samba DIOP, Chef du secteur des pêches de Kayar, animateurs de la journée, ont fait une... |
| Tipo: Report |
Palavras-chave: Mackerel fisheries; Marine accidents; Fish; Legislation; Law of the sea; Sea surface; Fish; Legislation; Http://aims.fao.org/aos/agrovoc/c_15903; Http://aims.fao.org/aos/agrovoc/c_4253. |
| Ano: 2002 |
URL: http://hdl.handle.net/1834/1741 |
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| The Third Session of the IODE Steering Group for Global Ocean Surface Underway Data (GOSUD) Pilot Project was held in Monterey, USA, from 3-4 November 2003. During this session the Steering Group reviewed the activities of the intersessional period and the accomplishments to date. The GOSUD Global Data Assembly Centre (GDAC) has been established at Coriolis, France, who will build the ftp structure to provide access to the underway data. It is also expected that http access will be developed. The Group also reviewed the tasks identified in the Project Plan and assigned leaders for the uncompleted tasks and established target dates. The project will seek to raise its profile within the scientific community during the next year. |
| Tipo: Report |
Palavras-chave: Oceanographic data; Sea surface. |
| Ano: 2003 |
URL: http://hdl.handle.net/1834/4328 |
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| Pottier, C; Garcon, V; Larnicol, G; Sudre, J; Schaeffer, P; Le Traon, Pierre-yves. |
| Two approaches of ocean color data merging were tested and compared in the North and Equatorial Atlantic Basin: the weighted averaging and the objective analysis. The datasets used were the daily level-3 binned data of chlorophyll-a from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer on the Aqua satellite over the year 2003, which is the first common full year of operation. Since they represent input for both approaches, matchups between the satellite and the in situ data from the SeaWiFS Bio-optical Archive and Storage System and the Atlantic Meridional Transect were first studied to compute a spatial map of the root mean-square error and of the bias. Because of the log distribution of the chlorophyll... |
| Tipo: Text |
Palavras-chave: Signal analysis; Sea surface; Marine vegetation; Biology. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-3631.pdf |
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| Plaisant, M. |
| Empirical models already exist for ambient noise spectral density function of frequency, sea state or wind speed but they give no information on the spatial structure or coherence of the noise field which is essential as soon as array beamforming is involved. We have developed a model which computes the spatial coherence matrix of the noise field due to a continuous distribution of sources located at the sea surface, and also the noise power spectral density after classical beamforming on an equidistant hydrophones linear array. In this model, propagation effects like rays bending due to variations of index of refraction and multiple bottom and surface reflections are taken into account. Principles of the modeling are presented and results demonstrate that... |
| Tipo: Text |
Palavras-chave: Spectral analysis; Models; Wind speed; Sea surface; Surface water waves; Acoustic equipment; Sound waves; Underwater noise; Ambient noise. |
| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/1990/acte-1143.pdf |
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| Hauser, Daniele; Tourain, Cedric; Hermozo, Laura; Alraddawi, D.; Aouf, L.; Chapron, Bertrand; Dalphinet, A.; Delaye, L.; Dalila, M.; Dormy, E.; Gouillon, F.; Gressani, Victor; Grouazel, Antoine; Guitton, Gilles; Husson, R.; Mironov, Alexey; Mouche, Alexis; Ollivier, A.; Oruba, L.; Piras, E.; Suquet, R. Rodriguez; Schippers, P.; Tison, C.; Tran, Ngan. |
| This article describes the first results obtained from the Surface Waves Investigation and Monitoring (SWIM) instrument carried by the China France Oceanography Satellite (CFOSAT), which was launched on October 29, 2018. SWIM is a Ku-band radar with a near-nadir scanning beam geometry. It was designed to measure the spectral properties of surface ocean waves. First, the good behavior of the instrument is illustrated. It is then shown that the nadir products (significant wave height, normalized radar cross section, and wind speed) exhibit an accuracy similar to standard altimeter missions, thanks to a new retracking algorithm, which compensates a lower sampling rate compared to standard altimetry missions. The off-nadir beam observations are analyzed in... |
| Tipo: Text |
Palavras-chave: Spaceborne radar; Radar cross-sections; Surface waves; Sea surface; Instruments; Altimeter; Ocean wave spectra; Radar measurements; Scatterometer; Sea surface; Spaceborne radar; Speckle noise. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00677/78869/81168.pdf |
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| Said, Faozi; Johnsen, Harald; Nouguier, Frederic; Chapron, Bertrand; Engen, Geir. |
| The generalized curvature ocean surface scattering model [general curvature model (GCM)] is extended and revisited. Two key steps are addressed in this paper, namely, a necessary sea surface spectrum undressing procedure and the inclusion of a skewness phase-related component. Normalized radar cross-section (NRCS) simulations are generated at C-band for various wind conditions, polarizations, and incidence angles. Results are compared with CMOD5.n. Although the sea surface spectrum undressing procedure is a necessary step, the overall NRCS dynamic is notably affected only in low wind conditions (<= 5 m/s). The inclusion of the skewness phase-related component makes the most impact to the NRCS dynamic where the upwind/downwind asymmetry is clearly... |
| Tipo: Text |
Palavras-chave: Geophysical measurements; Radar cross section; Remote sensing; Sea surface; Surface waves. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00409/52013/52725.pdf |
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| Mercier, Grégoire; Ardhuin, Fanny. |
| Spaceborne synthetic aperture radar (SAR) is well adapted to detect ocean pollution independently from daily or weather conditions. In fact, oil slicks have a specific impact on ocean wave spectra. Initial wave spectra may be characterized by three kinds of waves, namely big, medium, and small, which correspond physically to gravity and gravity-capillary waves. The increase of viscosity, due to the presence of oil damps gravity-capillary waves. This induces not only a damping of the backscattering to the sensor but also a damping of the energy of the wave spectra. Thus, local segmentation of wave spectra may be achieved by the segmentation of a multiscale decomposition of the original SAR image. In this paper, a semisupervised oil-slick detection is... |
| Tipo: Text |
Palavras-chave: Water pollution; Synthetic aperture radar; Sea surface; Satellite applications; Oil spill; Image analysis. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1948.pdf |
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| Wergeland, Morten; Kudryavtsev, Vladimir; Chapron, Bertrand; Brekke, Camilla; Johannessen, Johnny A.. |
| Radarsat-2 C-band quad-polarization SAR observations of crude oil, emulsion, and plant oil slicks acquired in the wind speed range from 4 to 8 m/s and incidence angles from 30 degrees to 50 degrees are analyzed to yield new insights into the attenuation of short waves and breaking waves by surface slicks in real conditions. To provide a direct quantitative assessment of the surface wave damping, the measurements are decomposed into polarization difference (PD), polarization ratio (PR), nonpolarized (NP), and cross-polarized (CP) components. The PD signals relate to the extent of Bragg damping in the slick areas, over which the PR is systematically higher than over the ambient sea surface. Attenuation of the breaking waves is revealed to affect both the CP... |
| Tipo: Text |
Palavras-chave: Oil pollution; Radar imaging; Sea surface; Surface waves. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00363/47460/47484.pdf |
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| Registros recuperados: 20 | |
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