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| Registros recuperados: 58 | |
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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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| Hauser, D.; Caudal, G.; Guimbard, Sebastien; Mouche, Alexis. |
| Radar observations of the sea surface at C-Band and small incidence angles are used to investigate some properties of the surface slope probability density function (pdf). The method is based on the analysis of the variation of the radar cross-section with incidence angle, assuming a backscattering process following the Geometrical Optics theory. First, we assess the limit of this model in our experimental configuration by using simulations of radar cross-sections with a more accurate backscattering model, namely the Physical Optics model. We show that roughness properties with scales larger than 12 cm can be analyzed in our configuration (C-Band, incidence 7 to 16 degrees). The radar data are then analyzed in terms of filtered mean square slope under the... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/00000/11028/33570.pdf |
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| Hasager, C. B.; Vincent, P.; Husson, Romain; Mouche, Alexis; Badger, M.; Pena, A.; Volker, P.; Badger, J.; Di Bella, A.; Palomares, A.; Cantero, E.; Correia, P. M. F.. |
| The aim of the paper is to present offshore wind farm wake observed from satellite Synthetic Aperture Radar (SAR) wind fields from RADARSAT-1/-2 and Envisat and to compare these wakes qualitatively to wind farm wake model results. From some satellite SAR wind maps very long wakes are observed. These extend several tens of kilometres downwind e.g. 70 km. Other SAR wind maps show near-field fine scale details of wake behind rows of turbines. The satellite SAR wind farm wake cases are modelled by different wind farm wake models including the PARK microscale model, the Weather Research and Forecasting (WRF) model in high resolution and WRF with coupled microscale parametrization. |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00275/38671/37155.pdf |
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| Combot, Clement; Mouche, Alexis; Knaff, John; Zhao, Yuan; Zhao, Yuan; Vinour, Leo; Quilfen, Yves; Chapron, Bertrand. |
| To produce more precise descriptions of air-sea exchanges under Tropical Cyclones (TCs), spaceborne Synthetic Aperture Radar (SAR) instruments provide unique capabilities to probe the ocean surface conditions, at very high spatial resolution, and on synoptic scales. Using highly-resolved (3 km) wind fields, an extensive database is constructed from Radarsat-2 and Sentinel-1 SAR acquisitions. Spanning 161 tropical cyclones, the database covers all TC intensity categories that have occurred in five different TC basins, and include 29 cases coincident with SFMR measurements. After locating the TC center, a specific methodology is applied to filter out areas contaminated by heavy precipitations to help extract, for each acquisition, the maximum wind speed... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00654/76589/77738.pdf |
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| Quilfen, Yves; Prigent, C; Chapron, Bertrand; Mouche, Alexis; Houti, N. |
| The physics of remote sensing sea surface measurements is still poorly understood under severe weather conditions. Wind vector algorithms are usually developed for non-precipitating atmospheres and for wind speeds less than 20 m/s. In this study, we analyze observations from the QuikSCAT Ku-band scatterometer collocated with the WindSat full polarimetric microwave radiometer to estimate the potential of these two instruments for sea surface wind retrieval under severe weather conditions. The Jason altimeter provides independent measurements of wind speed and rain rate for comparison purposes. The sensitivity of the radar cross-sections and brightness temperatures to the wind speed and direction is directly studied from the observations and compared with... |
| Tipo: Text |
Palavras-chave: Winds; Scatterometer; Radiometer. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-6393.pdf |
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| 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... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00016/12712/9639.pdf |
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| Mouche, Alexis; Chapron, Bertrand; Reul, Nicolas; Hauser, D; Quilfen, Yves. |
| [1] Asymptotic models ( small perturbation and small slope approximation at first-order, Kirchhoff approximation or two-scale model) used to predict the normalized radar cross section of the sea surface generally fail to reproduce in detail backscatter radar measurements. In particular, the predicted polarization ratio versus incidence and azimuth angles is not in agreement with experimental data. This denotes the inability of these standard models to fully take into account the roughness properties with respect to the sensor's configuration of measurement ( frequency, incidence, and polarization). On the basis of particular assumptions, to decompose the scattered electromagnetic field between zones covered with freely propagating waves and others where... |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3577.pdf |
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| Hasager, Charlotte B.; Mouche, Alexis; Badger, Merete; Bingol, Ferhat; Karagali, Ioanna; Driesenaar, Tilly; Stoffelen, Ad; Pena, Alfredo; Longepe, Nicolas. |
| The offshore wind climatology in the Northern European seas is analysed from ten years of Envisat synthetic aperture radar (SAR) images using a total of 9256 scenes, ten years of QuikSCAT and two years of ASCAT gridded ocean surface vector wind products and high-quality wind observations from four meteorological masts in the North Sea. The traditional method for assessment of the wind resource for wind energy application is through analysis of wind speed and wind direction observed during one or more years at a meteorological mast equipped with well-calibrated anemometers at several levels. The cost of such measurements is very high and therefore they are only sparsely available. An alternative method is the application of satellite remote sensing.... |
| Tipo: Text |
Palavras-chave: Offshore wind; SAR; QuikSCAT; ASCAT; Wind energy; Resource; Northern Europe. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00239/35007/33542.pdf |
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| Li, Xiuzhong; Zhang, Biao; Mouche, Alexis; He, Yijun; Perrie, William. |
| This paper reports Ku-band normalized radar cross section (NRCS) at low incidence angles ranging from 0° to 18° and in the wind speed range from 6 to 70 m/s. The precipitation radar onboard the tropical rainfall measuring mission and Jason-1 and 2 have provided 152 hurricanes observations between 2008 and 2013 that were collocated with stepped-frequency microwave radiometer measurements. It is found that the NRCS decreases with increasing incidence angle. The decrease is more dramatic in the 40–70 m/s range of wind speeds than in the 6–20 m/s range, indicating that the NRCS is very sensitive to low incidence angles under extreme wind conditions and insensitive to the extreme wind speed. Consequently, the sea surface appears relatively “smooth” to Ku-band... |
| Tipo: Text |
Palavras-chave: NRCS; Extreme wind conditions; Low incidence angles. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00385/49659/50197.pdf |
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| Rascle, Nicolas; Nouguier, Frederic; Chapron, Bertrand; Mouche, Alexis; Ponte, Aurelien. |
| At times, high resolution images of sea surface roughness can provide stunning details of submesoscale upper ocean dynamics. As interpreted, transformations of short scale wind waves by horizontal current gradients are responsible for those spectacular observations. Those observations could prove particularly useful to validate numerical ocean models which reach increasingly high resolutions. Focusing on surface roughness at optical wavelengths, two steps have recently been performed in that direction. First, it was shown by Rascle et al. (2014, Journal of Physical Oceanography) that surface roughness variations not only trace surface current divergence but also other characteristics of the current gradient tensor, mainly the strain in the wind direction.... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00358/46878/46759.pdf |
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| Mouche, Alexis; Chapron, Bertrand; Reul, Nicolas; Collard, F. |
| Sea surface motions can produce different measured Doppler shifts with respect to instrumental configurations (incidence angle, electromagnetic wavelength, polarization). Under Gaussian statistics for the sea surface elevation and in the general framework of asymptotic theories for ocean surface electromagnetic wave scattering, Doppler shifts can be predicted. The small-slope, Kirchhoff, local curvature and resonant curvature approximations are compared in the backscatter configuration. Predicted Doppler shifts for Kirchhoff and small-slope approximations in co-polarized configuration are insensitive to the polarization state. On the other hand, the local and resonant curvature solutions, through a phase perturbation formalism, yield to significant... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3576.pdf |
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| Ardhuin, Fabrice; Stopa, Justin; Chapron, Bertrand; Collard, Fabrice; Husson, Romain; Jensen, Robert E.; Johannessen, Johnny; Mouche, Alexis; Passaro, Marcello; Quartly, Graham D.; Swail, Val; Young, Ian. |
| Sea state information is needed for many applications, ranging from safety at sea and on the coast, for which real time data are essential, to planning and design needs for infrastructure that require long time series. The definition of the wave climate and its possible evolution requires high resolution data, and knowledge on possible drift in the observing system. Sea state is also an important climate variable that enters in air-sea fluxes parameterizations. Finally, sea state patterns can reveal the intensity of storms and associated climate patterns at large scales, and the intensity of currents at small scales. A synthesis of user requirements leads to requests for spatial resolution at kilometer scales, and estimations of trends of a few centimeters... |
| Tipo: Text |
Palavras-chave: Sea state; Waves; Altimeter; SAR; Swell; Remote sensing; Buoy; Microseisms. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00489/60090/63432.pdf |
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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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| Hauser, D.; Tison, C.; Amiot, T.; Delaye, L.; Mouche, Alexis; Guitton, Gilles; Aouf, L.; Castillan, P.. |
| CFOSAT (the China France Oceanography Satellite) is a joint mission from the Chinese and French Space Agencies, devoted to the observation ocean surface wind and waves so as to improve wind and wave forecast for marine meteorology, ocean dynamics modeling and prediction, climate variability knowledge, fundamental knowledge of surface processes. Currently under Phase D (manufacturing phase), the launch is now planned for mid-2018 the later. The CFOSAT will carry two payloads, both Ku-Band radar: the wave scatterometer (SWIM) and the wind scatterometer (SCAT). Both instruments are based on new concepts with respect to existing satellite-borne wind and wave sensors. Indeed, one of the originalities of CFOSAT is that it will provide simultaneously and in the... |
| Tipo: Text |
Palavras-chave: Satellite; Radar; Surface ocean waves; Surface ocean wind; Scatterometer; CFOSAT. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00363/47468/47487.pdf |
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| Duong, Quoc-phi; Langlade, Sébastien; Payan, Christophe; Husson, Romain; Mouche, Alexis; Malardel, Sylvie. |
| Tropical cyclone (TC) monitoring and forecast in the South West Indian Ocean (SWIO) basin remain challenging, notably because of the lack of direct observations. During the 2018–2019 cyclone season, S-1 Sentinel SAR images were acquired, as part of the ReNovRisk-Cyclone research program, giving access to unprecedented detailed TC wind structure description without wind speed limitation. This paper assesses the quality of these data and the impact of their assimilation for TC forecasts. SAR observations are compared with analyses from a convection-permitting, limited area model AROME OI 3D-Var and with wind products used for operational TC monitoring. Their bias depends on the angle of incidence of the radar and the observation error is larger for extreme... |
| Tipo: Text |
Palavras-chave: SAR; 3D-Var; Data assimilation; Tropical cyclone; Sentinel; IDAI; GELENA. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00692/80373/83490.pdf |
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| Jiang, Haoyu; Stopa, Justin; Wang, He; Husson, Romain; Mouche, Alexis; Chapron, Bertrand; Chen, Ge. |
| A method for systematically tracking swells across oceanic basins is developed by taking advantage of high-quality data from space-borne altimeters and wave model output. The evolution of swells is observed over large distances based on 202 swell events with periods ranging from 12 to 18 s. An empirical attenuation rate of swell energy of about 4 × 10−7 m−1 is estimated using these observations, and the nonbreaking energy dissipation rates of swells far away from their generating areas are also estimated using a point source model. The resulting acceptance range of nonbreaking dissipation rates is −2.5 to 5.0 × 10−7 m−1, which corresponds to a dissipation e-folding scales of at least 2000 km for steep swells, to almost infinite for small-amplitude swells.... |
| Tipo: Text |
Palavras-chave: Altimeter; Swell dissipation; Swell tracking. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00314/42526/41897.pdf |
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| Wang, He; Mouche, Alexis; Husson, Romain; Chapron, Bertrand. |
| Synthetic Aperture Radar (SAR) in wave mode is a powerful sensor for monitoring the swells propagating across ocean basins. Here, we investigate crossing swells in the Indian Ocean using 10-years Envisat SAR wave mode archive spanning from December 2003 to April 2012. Taking the benefit of the unique "fireworks" analysis on SAR observations, we reconstruct the origins and propagating routes that are associated with crossing swell pools in the Indian Ocean. Besides, three different crossing swell mechanisms are discriminated from space by the comparative analysis between results from "fireworks" and original SAR data: (1) in the mid-ocean basin of the Indian Ocean, two remote southern swells form the crossing swell; (2) wave-current interaction; and, (3)... |
| Tipo: Text |
Palavras-chave: Crossing swells; Synthetic aperture radar; Wave mode; Fireworks analysis; Indian Ocean. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00679/79110/81601.pdf |
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| Registros recuperados: 58 | |
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