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Registros recuperados: 6
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A C-Band Geophysical Model Function for Determining Coastal Wind Speed Using Synthetic Aperture Radar ArchiMer
Lu, Yiru; Zhang, Biao; Perrie, William; Mouche, Alexis; Li, Xiaofeng; Wang, He.
A new geophysical model function (GMF), called C_SARMOD2, has been developed to relate high-resolution C-band normalized radar cross section (NRCS), acquired in VV polarization over the ocean, to the 10-m height wind speed. A total of 3078 RADARSAT-2 and Sentinel-1A VV-polarized synthetic aperture radar (SAR) images, acquired under different wind speed conditions, were collocated with in situ buoy measurements. The paired dataset was used to derive transfer functions and coefficients of C_SARMOD2, and then to validate the wind speed retrievals. The comparison between SAR-retrieved wind speeds and buoy measurements show almost no bias and a root mean square error of 1.84 m/s. Two representative quad-and dual-polarization SAR images, acquired from coastal...
Tipo: Text Palavras-chave: Coastal wind speed; Geophysical model function (GMF); Synthetic aperture radar (SAR).
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00452/56390/60555.pdf
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Error Analysis on ESA's Envisat ASAR Wave Mode Significant Wave Height Retrievals Using Triple Collocation Model ArchiMer
Wang, He; Zhu, Jianhua; Yang, Jingsong.
Nowadays, spaceborne Synthetic Aperture Radar (SAR) has become a powerful tool for providing significant wave height (SWH). Traditionally, validation of SAR derived SWH has been carried out against buoy measurements or model outputs, which only yield an inter-comparison, but not an "absolute" validation. In this study, the triple collocation error model has been introduced in the validation of Envisat ASAR derived SWH products. SWH retrievals from ASAR wave mode using ESA's algorithm are validated against in situ buoy data, and wave model hindcast results from WaveWatch III wave model, covering a period of six years. From the triple collocation validation analysis, the impacts of the collocation distance and water depth on the error of ASAR SWH are...
Tipo: Text Palavras-chave: Envisat ASAR; Significant wave height; Validation; Triple collocation.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00249/36019/34545.pdf
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GF-3 SAR Ocean Wind Retrieval: The First View and Preliminary Assessment ArchiMer
Wang, He; Yang, Jingsong; Mouche, Alexis; Shao, Weizeng; Zhu, Jianhua; Ren, Lin; Xie, Chunhua.
Gaofen-3 (GF-3) is the first Chinese civil C-band synthetic aperture radar (SAR) launched on 10 August 2016 by the China Academy of Space Technology (CAST), which operates in 12 imaging modes with a fine spatial resolution up to 1 m. As one of the primary users, the State Oceanic Administration (SOA) operationally processes GF-3 SAR Level-1 products into ocean surface wind vector and plans to officially release the near real-time SAR wind products in the near future. In this paper, the methodology of wind retrieval at C-band SAR is introduced and the first results of GF-3 SAR-derived winds are presented. In particular, the case of the coastal katabatic wind off the west coast of the U.S. captured by GF-3 is discussed. The preliminary accuracy assessment of...
Tipo: Text Palavras-chave: GF-3; Synthetic aperture radar (SAR); Ocean surface wind; Validation.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00396/50731/51435.pdf
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Limitation of SAR Quasi-Linear Inversion Data on Swell Climate: An Example of Global Crossing Swells ArchiMer
Jiang, Haoyu; Mouche, Alexis; Wang, He; Babanin, Alexander V.; Chapron, Bertrand; Chen, Ge.
Numerical wave models are powerful tools for investigating global wave climate. Here a global wave hindcast is employed to estimate the global pattern of crossing swells. However, the global patterns of crossing swells derived from the model are different from those derived from the synthetic aperture radar (SAR) wave mode products of quasi-linear inversion, indicating one of them is questionable. The comparison shows that the first two most energetic swells inversed by SAR are often not in accordance with the first two most energetic swells in the model, and this will have a large impact on the statistics of the data. Before this problem is solved, SAR wave products of quasi-linear inversion should be treated with care in wave climate studies.
Tipo: Text Palavras-chave: Synthetic aperture radar; Quasi-linear inversion; Crossing swells; Wave climate.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00369/47979/48003.pdf
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Preliminary Analysis of Chinese GF-3 SAR Quad-Polarization Measurements to Extract Winds in Each Polarization ArchiMer
Ren, Lin; Yang, Jingsong; Mouche, Alexis; Wang, He; Wang, Juan; Zheng, Gang; Zhang, Huaguo.
This study analyzed the noise equivalent sigma zero (NESZ) and ocean wind sensitivity for Chinese C-band Gaofen-3 (GF-3) quad-polarization synthetic aperture radar (SAR) measurements to facilitate further operational wind extraction from GF-3 data. Data from the GF-3 quad-polarization SAR and collocated winds from both NOAA/NCEP Global Forecast System (GFS) atmospheric model and National Data Buoy Center (NDBC) buoys were used in the analysis. For NESZ, the co-polarization was slightly higher compared to the cross-polarization. Regarding co-polarization and cross-polarization, NESZ was close to RadarSAT-2 and Sentinel-1 A. Wind sensitivity was analyzed by evaluating the dependence on winds in terms of normalized radar cross-sections (NRCS) and polarization...
Tipo: Text Palavras-chave: Gaofen-3; Synthetic aperture radar; Quad-polarization; Ocean surface wind; Noise equivalent sigma zero; Geophysical model function; Polarization ratio; Polarization difference.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00420/53104/54059.pdf
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Tracking the attenuation and nonbreaking dissipation of swells using altimeters ArchiMer
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
Registros recuperados: 6
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