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Analyse spectrale et statistique vent-vagues des images radar à ouverture synthétique - Application aux données des satellites ERS-1/2 ArchiMer
Kerbaol, Vincent.
Le radar à ouverture synthétique (ROS) est le seul instrument à fournir une information directionnelle des vagues grâce à sa haute résolution. Toutefois, l'inversion des spectres 2-D ROS, afin de restituer le spectre de la mer, est rendue difficile par la forte distortion spectrale causée par le filtrage passe-bas dans la direction de déplacement de l'instrument (azimut). Ce filtrage est issu des composantes radiales des mouvements sur la surface qui affectent l'information Doppler nécessaire à la reconstruction de l'image. De plus, le coefficient de rétrodiffusion ?°, permettant d'estimer le vent à l'aide de modèles empiriques, est fréquemment saturé lors de la quantification du signal. Les limitations actuelles démontrent donc la nécessité d'améliorer...
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Ano: 1997 URL: http://archimer.ifremer.fr/doc/00132/24353/22352.pdf
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Analysis of ERS-1/2 synthetic aperture radar wave mode imagettes ArchiMer
Kerbaol, Vincent; Chapron, Bertrand; Vachon, Paris W.
The European Space Agency (ESA) ERS-1 and ERS-2 C band VV polarization active microwave instrument (AMI) offers the unique ability to combine interlaced wind scatterometer and high-resolution synthetic aperture radar (SAR) wave mode imagettes. In this study, more than 2000 imagettes were considered. Each imagette has been statistically analyzed in comparison with normalized radar cross-section (NRCS) measurements from the scatterometer mode. During ti lt ERS-1 AMI wave mode mission the incidence angle of the imagette center was modified from roughly 19.9 degrees to 23.5 degrees. Using ERS-1 and ERS-2 NRCS, calibration has thus been completed for both configurations, which allows a better characterization of some signal data saturation effects. However,...
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Ano: 1998 URL: http://archimer.ifremer.fr/doc/00447/55869/58014.pdf
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Improved near real time surface wind resolution over the Mediterranean Sea ArchiMer
Bentamy, Abderrahim; Ayina, Ludos-herve; Queffeulou, Pierre; Croize-fillon, Denis; Kerbaol, Vincent.
Several scientific programs, including the Mediterranean Forecasting System Toward Environmental Predictions (MFSTEP project), request high space and time resolutions of surface wind speed and direction. The purpose of this paper is to focus on surface wind improvements over the global Mediterranean Sea, based on the blending near real time remotely sensed wind observations and ECMWF wind analysis. Ocean surface wind observations are retrieved from QuikSCAT scatterometer and from SSM/I radiometers available at near real time at Meteo-France. Using synchronous satellite data, the number of remotely sensed data available for each analysis epoch ( 00: 00 h; 06: 00 h; 12: 00 h; 18: 00 h) is not uniformly distributed as a function of space and time. On average...
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Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3528.pdf
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On the Use of Doppler Shift for Sea Surface Wind Retrieval From SAR ArchiMer
Mouche, Alexis; Collard, Fabrice; Chapron, Bertrand; Dagestad, Knut-frode; Guitton, Gilles; Johannessen, Johnny A.; Kerbaol, Vincent; Hansen, Morten Wergeland.
The synthetic aperture radar (SAR) Doppler centroid has been used to estimate the scatter line-of-sight radar velocity. In weak to moderate ocean surface current environment, the SAR Doppler centroid is dominated by the directionality and strength of wave-induced ocean surface displacements. In this paper, we show how this sea state signature can be used to improve surface wind retrieval from SAR. Doppler shifts of C-band radar return signals from the ocean are thoroughly investigated by colocating wind measurements from the ASCAT scatterometer with Doppler centroid anomalies retrieved from Envisat ASAR. An empirical geophysical model function (CDOP) is derived, predicting Doppler shifts at both VV and HH polarization as function of wind speed, radar...
Tipo: Text Palavras-chave: Doppler; Surface wind; Synthetic aperture radar (SAR).
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00088/19896/17554.pdf
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