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ABSOLUTE CALIBRATION OF THE ERS-2 SCATTEROMETER IN GYRO-LESS MODE USING TRANSPONDERS Gayana
Manise,Nicolas; Neyt,Xavier; Acheroy,Marc.
The scatterometer on-board ERS-2, earth-observation satellite developed by the European Space Agency, is an active real aperture radar instrument designed to measure the backscatter coefficient 0 from the earth. Its main utility is to measure physical parameters such as wind speeds and directions over the sea surface. Due to malfunctions of the on-board gyroscopes and even though a new attitude and orbit control system is used, the yaw-orientation of the spacecraft still exhibits random variations from the nominal attitude. This unpredictable attitude requires re-developing the calibration chain of the scatterometer instrument. Distributed targets, such as the rain forest, are used to perform a relative calibration while transponders situated at known...
Tipo: Journal article Palavras-chave: Scatterometer; Calibration; Transponder.
Ano: 2004 URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-65382004000300011
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ASCAT/MetOp scatterometer data : first results for sea ice study ArchiMer
Ardhuin, Fanny; Ezraty, Robert; Croize-fillon, Denis.
Backscatter values from scatterometers are commonly used to estimate wind field over oceans, their ability to monitor sea ice coverage, age and drift has been also demonstrated. Here, ASCAT backscatter coefficient has been processed for sea ice geophysical interpretation in order to increase the long time series of ice parameters already available. It has been shown that incidence- adjustment is mandatory for geophysical meaning, the backscatter maps enable the discrimination between multi year ice and first year ice, these maps can also be used as a basic product for sea ice drift estimation. (Copyright : European Space Agency ISBN 978-92-9221-239-1 ISSN 1609-042X)
Tipo: Text Palavras-chave: Sea ice; Wind; Scatterometer; ASCAT; MetOp; Glaces de mer; Vent; Diffusiomètre; ASCAT; MetOp.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/acte-6970.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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CFOSAT: A new Chinese-French satellite for joint observations of ocean wind vector and directional spectra of ocean waves ArchiMer
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: http://archimer.ifremer.fr/doc/00363/47468/47487.pdf
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Homogenization of scatterometer wind retrievals ArchiMer
Bentamy, Abderrahim; Grodsky, Semyon A.; Elyouncha, Anis; Chapron, Bertrand; Desbiolles, Fabien.
Surface winds (10 m equivalent neutral wind velocity) from scatterometer missions since 1992 to present require homogenization to meet the requirements for oceanic and atmospheric climate data records. Sources of differences between winds retrieved from different scatterometer measurements mainly arise from calibration/validation procedures used for each scatterometer and differences in measurement physics. In this study, we focus on the calibration/validation component of the European Remote Sensing Satellite (ERS)-1 and ERS-2 wind speed biases. ERS-1 and ERS-2 data, named as WNF products, are from the Institut Français de Recherche pour l'Exploitation de la MER (IFREMER). In addition to WNF data, the newly calibrated ERS-2 products provided by the...
Tipo: Text Palavras-chave: Scatterometer; Surface wind; Homogenization.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00334/44536/44468.pdf
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Impact of rain cell on scatterometer data: 1. Theory and modeling - art. no. 3225 ArchiMer
Tournadre, Jean; Quilfen, Yves.
[1] The two scatterometers currently in operation, the Ku-band NASA Seawinds on the QuikScat satellite and the C-band AMI-Wind on the ERS-2 satellite, are designed to infer the ocean wind vectors from sea surface radar backscatter measurements. They provide excellent coverage of the ocean, and their wind products are of great value for ocean and meteorological communities. However, the presence of rain within scatterometer cells can significantly modify the sea surface backscatter coefficient and hence alter the wind vector retrieval. These perturbations can hamper the analysis of wind fields within atmospheric low-pressure systems or tropical cyclones. Rain perturbations result from volume scattering and attenuation by raindrops in the atmosphere as well...
Tipo: Text Palavras-chave: Model of interaction; Ocean surface winds; Rain; Scatterometer.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/2003/publication-513.pdf
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Impact of rain cell on scatterometer data: 2. Correction of Seawinds measured backscatter and wind and rain flagging ArchiMer
Tournadre, Jean; Quilfen, Yves.
In October and early November 1999, the GOGP99 experiment collected hydrological, currentmeter, tide recorder, thermistor and drifting buoy data near the Strait of Hormuz. Data analysis provides the water mass structure in the Strait: Persian Gulf Water (PGW) core is banked against the Omani coast, while Indian Ocean Surface Water (IOSW) lies near the Iranian coast. These water masses are most often covered by a homogeneous surface layer. Thermohaline characteristics of the PGW core decrease substantially downstream, from the Persian/Arabian Gulf to the Gulf of Oman. PGW and IOSW thermohaline characteristics and distribution also exhibit notable changes at periods shorter than a month as shown by repeated hydrological sections. The tidal signal measured...
Tipo: Text Palavras-chave: Wind retrieval; Rain; Scatterometer.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-388.pdf
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Prediction of sea level anomalies using ocean circulation model forced by scatterometer wind and validation using TOPEX/Poseidon data ArchiMer
Quilfen, Yves; Bentamy, Abderrahim; Delecluse, P; Katsaros, K; Grima, N.
Uncertainties in the surface wind field have long been recognized as a major limitation in the interpretation of results obtained by oceanic circulation models. It is especially true in the tropical oceans, where the response to wind forcing is very strong on short time scales. The purpose of this paper is to show that these uncertainties can be greatly reduced by using spaceborne wind sensors that provide accurate measurements on a global basis.Surface winds over the global oceans have been measured by scatterometry since the launch of the European Remote Sensing Satellite (ERS-1) in August 1991 by the European Space Agency, Noordwijk, The Netherlands, and is currently provided by ERS-2, launched in April 1995. The ground track wind vectors are processed...
Tipo: Text Palavras-chave: Ocean model; Ocean surface; Scatterometer; Sea level.
Ano: 2000 URL: http://archimer.ifremer.fr/doc/00000/10501/9560.pdf
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Review and assessment of latent and sensible heat flux accuracy over the global oceans ArchiMer
Bentamy, Abderrahim; Piolle, Jean-francois; Grouazel, Antoine; Danielson, R.; Gulev, S.; Paul, Frederic; Azelmat, Hamza; Mathieu, P. P.; Von Schuckmann, Karina; Sathyendranath, S.; Evers-king, H.; Esau, I.; Johannessen, J. A.; Clayson, C. A.; Pinker, R. T.; Grodsky, S. A.; Bourassa, M.; Smith, S. R.; Haines, K.; Valdivieso, M.; Merchant, C. J.; Chapron, Bertrand; Anderson, A.; Hollmann, R.; Josey, S. A..
For over a decade, several research groups have been developing air-sea heat flux information over the global ocean, including latent (LHF) and sensible (SHF) heat fluxes over the global ocean. This paper aims to provide new insight into the quality and error characteristics of turbulent heat flux estimates at various spatial and temporal scales (from daily upwards). The study is performed within the European Space Agency (ESA) Ocean Heat Flux (OHF) project. One of the main objectives of the OHF project is to meet the recommendations and requirements expressed by various international programs such as the World Research Climate Program (WCRP) and Climate and Ocean Variability, Predictability, and Change (CLIVAR), recognizing the need for better...
Tipo: Text Palavras-chave: Ocean Heat Flux; Latent heat flux; Sensible heat flux; Ocean heat content; Scatterometer; Surface wind; Specfic air humidity; OceanSites; Remotely sensed data.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00403/51403/53729.pdf
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Sea Surface Ka-Band Doppler Measurements: Analysis and Model Development ArchiMer
Yurovsky, Yury; Kudryavtsev, Vladimir; Grodsky, Semyon; Chapron, Bertrand.
Multi-year field measurements of sea surface Ka-band dual-co-polarized (vertical transmit–receive polarization (VV) and horizontal transmit–receive polarization (HH)) radar Doppler characteristics from an oceanographic platform in the Black Sea are presented. The Doppler centroid (DC) estimated using the first moment of 5 min averaged spectrum, corrected for measured sea surface current, ranges between 0 and ≈1 m/s for incidence angles increasing from 0 to 70∘ . Besides the known wind-to-radar azimuth dependence, the DC can also depend on wind-to-dominant wave direction. For co-aligned wind and waves, a negative crosswind DC residual is found, ≈−0.1 m/s, at ≈20 ∘ incidence angle, becoming negligible at ≈ 60 ∘ , and raising to, ≈+0.5 m/s, at 70∘ . For our...
Tipo: Text Palavras-chave: Radar; Scatterometer; Ocean; Backscatter; Doppler shift; Doppler centroid; Sea surface current; Wind drift; Modulation; Transfer function; Empirical model.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00489/60077/63399.pdf
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Simultaneous ocean surface current and wind vectors retrieval with squinted SAR interferometry: Geophysical inversion and performance assessment ArchiMer
Martin, Adrien Ch; Gommenginger, Christine P.; Quilfen, Yves.
Simultaneous measurements of ocean surface current and wind vectors at the ocean submesoscale (O [1–10 km]) are needed to improve our understanding of upper ocean mixing, air-sea interactions, ocean biophysical processes and large-scale oceanic transports. A new satellite mission concept called SEASTAR aims to do just that. The concept is a Ku-band along-track interferometric Synthetic Aperture Radar (SAR) system with two squinted beams pointing ±45° from broadside and incidence angles around 30°. The paper presents an inversion strategy to retrieve simultaneously ocean surface current and wind vectors and reports on the performance obtained with different wind/current conditions and instrument configurations. Results are based on numerical simulations...
Tipo: Text Palavras-chave: Ocean surface current vector; Ocean wind vector; Doppler; Scatterometer; SAR; Along-track interferometry.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00445/55693/57436.pdf
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Spatial and temporal characteristics of wind and wind power off the coasts of Brittany ArchiMer
Bentamy, Abderrahim; Croize-fillon, Denis.
The main objective of this paper is to thoroughly examine the remotely sensed wind characteristics around the coasts of Brittany as well as some more specific areas. The offshore wind power potential is then assessed. To achieve this objective, information on wind speed and direction with sufficient spatial and temporal sampling under all weather conditions and during day and night is required. This study uses more than 12 years (December 1999–December 2012) of consistent remotely sensed data retrieved from the ASCAT and QuikSCAT scatterometers to estimate the conventional moments and associated wind distribution parameters. The latter are comparable to wind observations from meteorological stations. Furthermore, combining in-situ and scatterometer wind...
Tipo: Text Palavras-chave: Wind; Energy; Scatterometer; Remote sensing; Brittany.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00175/28648/28552.pdf
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The potential of QuikSCAT and WindSat observations for the estimation of sea surface wind vector under severe weather conditions - art. no. C09023 ArchiMer
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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Validation and analysis of ocean parameters using ASCAT data ArchiMer
Bentamy, Abderrahim; Ardhuin, Fanny; Croize-fillon, Denis; Queffeulou, Pierre.
This project aims to investigate the quality of ASCAT measurements as well as their use for oceanographic purposes. The accuracy of ASCAT retrievals will be mainly based on the use of collocated data from moored buoys, numerical weather prediction models, and satellites. The resulting collocated data will be used to explore the accuracy of the geophysical model function which relates the backscatter coefficients to surface wind vectors, as well as to assess the quality of ASCAT vector winds at global and local scales. Once this objective reached, it will enable to fully utilize the MetOp data for oceanographic applications. They will contribute to evaluate various estimates of ocean surface flux parameters required to force ocean general circulation...
Tipo: Text Palavras-chave: Fluxes; Sea ice; Wind; Scatterometer; ASCAT; MetOp; Flux; Glaces de mer; Vent; Diffusiomètre; ASCAT; MetOp.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/acte-1272.pdf
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Validation of Arctic sea ice drift with IABP buoys ArchiMer
Ardhuin, Fanny; Ezraty, Robert.
Satellites enable daily and global coverage of the polar oceans, providing an unique monitoring capability of sea ice dynamics over Arctic and Antarctic. Available geophysical parameters include ice concentration, extent, type and sea ice drift. Backscatter map from SeaWinds/QuikSCAT and brightness temperature maps from Special Sensor Microwave Imager (SSM/I) are available at a pixel resolution of 12,5 km from which ice drift can be estimated for each sensor. Since 1999, IFREMER makes available a "Merged" sea ice drift data set based on the combination of these drifts at 3 and 6-day lags at the grid resolution of 62,5 km. It has been demonstrated that combining these drifts increases the number of valid vectors. In this paper, the validation of this...
Tipo: Text Palavras-chave: Arctic; Buoys; Drift; Sea ice; AMSR E; Radiometer; Scatterometer; Arctique; Bouées; Dérive; Glaces de mer; AMSR E; Radiomètre; Diffusiomètre.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/acte-1292.pdf
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