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Registros recuperados: 10
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A dual-frequency approach for retrieving sea surface wind speed from TOPEX altimetry ArchiMer
Chen, G; Chapron, Bertrand; Ezraty, Robert; Vandemark, D.
More than a dozen of wind speed (U) algorithms have been proposed during the past 2 decades, as a result of a continuing effort to improve altimeter wind measurement. The progress in terms of accuracy, however, is seen to be rather slow. The reported root mean square (RMS) error of prevailing algorithms varies mostly between 1.6 and 2.0 m/s for the dominant wind regime. As far as the TOPEX altimeter is concerned, three measured quantities, namely, the radar cross sections from Ku and C band (sigma(Ku) and sigma(C)), as well as the significant wave height (H-s), have been used in previous algorithm developments, resulting in a variety of single-, dual-, and three-parameter model functions. On the basis of the finding of a banded dependency of the...
Tipo: Text Palavras-chave: Sea surface wind speed; Retrieval; TOPEX; Altimeter; Dual frequency.
Ano: 2002 URL: https://archimer.ifremer.fr/doc/00000/10224/9579.pdf
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AltiKa: a Ka-band altimetry payload and system for operational altimetry during the GMES period ArchiMer
Vincent, Patrick; Steunou, N; Caubet, E; Phalippou, L; Rey, L; Thouvenot, E; Verron, J.
This paper describes the Ka-band altimetry payload and system that has been studied for several years by CNES, ALCATEL SPACE and some science laboratories. Altimetry is one of the major elements of the ocean observing system to be made sustainable through the GEOSS ( Global Earth Observation System of Systems) and GMES ( Global Monitoring of the Environment and Security) programs. A short review of some mission objectives to be fulfilled in terms of mesoscale oceanography in the frame of the GEOSS and GMES programs is performed. To answer the corresponding requirements, the approach consisting in a constellation of nadir altimeter is discussed. A coupled Ka-band altimeter-radiometer payload is then described; technical items are detailed to explain how...
Tipo: Text Palavras-chave: Altimeter; Radiometer; Ocean mesoscale circulation; Ka-band.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/00284/39508/38003.pdf
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Assessment of wind-forcing impact on a global wind-wave model using the TOPEX altimeter ArchiMer
Feng, H; Vandemark, D; Quilfen, Yves; Chapron, Bertrand; Beckley, B.
The study presents assessment of an operational wave model (Wavewatch III), focusing upon the model sensitivity to wind-forcing products. Four wind fields are used to drive the model, including the NCEP/NCAR reanalysis and three other products that assimilate various satellite wind measurements having high spatial resolution, including the QuikSCAT scatterometer. Three wave field statistics: significant wave height, mean zero-crossing wave period, and mean square slope are compared with collocated TOPEX altimeter derivatives to gauge the relative skill of differing wind-forced model runs, as well as to demonstrate an extended use of the altimeter beyond simply supplying wave height for wave model validation and assimilation. Results suggest that model...
Tipo: Text Palavras-chave: Sea state bias; Wind forcing; Scatterometer; Altimeter; Wave modeling.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1861.pdf
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Combined wind vector and sea state impact on ocean nadir-viewing Ku- and C-band radar cross-sections ArchiMer
Tran, Ngan; Chapron, Bertrand.
The authors report the first results in studying the polarization anisotropy of the microwave backscatter from nadir observations provided by Jason-1 altimeter in both Ku- and C-band. A small but clear wind direction signal for wind speeds above 6 m/s is revealed. These azimuthal variations of radar cross-section increase with increasing wind speed up to 14 m/s. The signatures then level off at higher winds. These results extend, for the first time, recent theoretical improved scattering approximation, and point some similarities between scattering and emission mechanisms at nadir. The observed directional effect can thus be interpreted as a signature of the curvature anisotropy of wind-generated short-scale waves. Sensitivities to both wind speed and sea...
Tipo: Text Palavras-chave: Altimeter; Radar cross section; Polarization; Wind direction; Sea state.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/00004/11557/8150.pdf
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Impacts of oil spills on altimeter waveforms and radar backscatter cross-section ArchiMer
Cheng, Yongcun; Tournadre, Jean; Li, Xiaofeng; Xu, Qing; Chapron, Bertrand.
Ocean surface films can damp short capillary-gravity waves, reduce the surface mean square slope, and induce “sigma0 blooms” in satellite altimeter data. No study has ascertained the effect of such film on altimeter measurements due to lack of film data. The availability of Environmental Response Management Application (ERMA) oil cover, daily oil spill extent and thickness data acquired during the Deepwater Horizon (DWH) oil spill accident provides a unique opportunity to evaluate the impact of surface film on altimeter data. In this study, the Jason-1/2 passes nearest to the DWH platform are analyzed to understand the waveform distortion caused by the spill as well as the variation of σ0 as a function of oil thickness, wind speed and radar band. Jason-1/2...
Tipo: Text Palavras-chave: Oil spill; Altimeter; Sigma0 bloom; Waveform.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00381/49203/49635.pdf
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Observing Sea States ArchiMer
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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Overview of (Sub)mesoscale Ocean Dynamics for the NAAMES Field Program ArchiMer
Della Penna, Alice; Gaube, Peter.
Tipo: Text Palavras-chave: Mesoscale; Eddies; North Atlantic aerosols and marine ecosystems study; North Atlantic; NAAMES; Altimeter; Satellite oceanography; Lagrangian reanalysis.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00509/62022/66142.pdf
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SEA LEVEL VARIATIONS AND SEA SURFACE CIRCULATIONS IN THE KOREAN SEAS BY SATELLITE ALTIMETER DATA Gayana
Hong-Joo,Yoon; Yeong-Seup,Kim; Byong-Hyuk,Kwon.
Sea level variations and sea surface circulations in the Korean seas were observed by Topex/Poseidon altimeter data from 1993 through 1997. In sea level variations, the West and South Sea showed relatively high variations with comparison to the East Sea. Then, the northern and southern area in the West Sea showed the range of 20~30cm and 18~24cm, and the northern west of Jeju island and the southern west of Tsushima island in the South Sea showed the range of 15~20 cm and 10~15 cm, respectively. High variations in the West Sea was results to the inflow in sea surface of Yellow Sea Warm Current (YSWC) and bottom topography. Sea level variations in the South Sea was due to two branch currents (Jeju Warm Current and East Korea Warm Current) originated from...
Tipo: Journal article Palavras-chave: Sea level variations; Sea surface circulations; Altimeter.
Ano: 2004 URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-65382004000300051
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Sedimentation on intertidal mudflats in the lower part of macrotidal estuaries: Sedimentation rhythms and their preservation ArchiMer
Deloffre, J; Verney, Romaric; Lafite, R; Lesueur, P; Lesourd, S; Cundy, A.
The objective of this study is to propose an original approach to the analysis of the formation of intertidal rhythmites, their preservation, and the evaluation of sedimentation rates on estuarine mudflats. Three mudflats, one from each of three estuaries, were analysed using a combination of long-term (>a year), high-frequency (1 burst/10 or 20 min), and high-resolution (0.2 cm) altimeter datasets and X-ray images of sediment cores collected during topographic surveys. The results highlight the roles played by sediment supply, hydrodynamics, and morphology of the lower estuaries on the sedimentation rhythms. While the sediment-starved Medway estuary (Kent, UK) remains stable at different time-scales, the annual sedimentation rates on the sheltered...
Tipo: Text Palavras-chave: Macrotidal estuary; X ray imagery; Altimeter; Rhythmites; Mud; Morphology.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3517.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: 10
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