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A labelled ocean SAR imagery dataset of ten geophysical phenomena from Sentinel‐1 wave mode ArchiMer
Wang, Chen; Mouche, Alexis; Tandeo, Pierre; Stopa, Justin; Longépé, Nicolas; Erhard, Guillaume; Foster, Ralph C.; Vandemark, Douglas; Chapron, Bertrand.
The Sentinel‐1 mission is part of the European Copernicus program aiming at providing observations for Land, Marine and Atmosphere Monitoring, Emergency Management, Security and Climate Change. It is a constellation of two (Sentinel‐1 A and B) Synthetic Aperture Radar (SAR) satellites. The SAR wave mode (WV) routinely collects high‐resolution SAR images of the ocean surface during day and night and through clouds. In this study, a subset of more than 37,000 SAR images is labelled corresponding to ten geophysical phenomena, including both oceanic and meteorologic features. These images cover the entire open ocean and are manually selected from Sentinel‐1A WV acquisitions in 2016. For each image, only one prevalent geophysical phenomenon with its prescribed...
Tipo: Text Palavras-chave: Manual labelling; Ocean surface phenomena; Sentinel-1 wave mode; Synthetic aperture radar.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00512/62406/66659.pdf
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A new ocean SAR cross-spectral parameter: definition and directional property using the global Sentinel-1 measurements ArchiMer
Li, Huimin; Chapron, Bertrand; Mouche, Alexis; Stopa, Justin.
Space‐borne synthetic aperture radar (SAR) measurements have already been proven to be invaluable in detecting and quantifying properties of ocean swell systems. With the improved spatial resolution, Sentinel‐1 wave mode measurements can further be extended towards shorter scale waves, i.e. within the surface wave equilibrium range. In this study, a new parameter is derived from filtering SAR image cross‐spectra around range‐traveling intermediate wind waves (wavelengths 15‐20 m). This parameter captures both the radar cross section variability and its time evolution. Given the dependence of intermediate waves on local wind field, this parameter is statistically documented to confirm its sensitivity to both wind speed and wind direction. Comparable to...
Tipo: Text
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00482/59394/62160.pdf
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Comparison and validation of physical wave parameterizations in spectral wave models ArchiMer
Stopa, Justin; Ardhuin, Fabrice; Babanin, Alexander; Zieger, Stefan.
Recent developments in the physical parameterizations available in spectral wave models have already been validated, but there is little information on their relative performance especially with focus on the higher order spectral moments and wave partitions. This study concentrates on documenting their strengths and limitations using satellite measurements, buoy spectra, and a comparison between the different models. It is confirmed that all models perform well in terms of significant wave heights; however higher-order moments have larger errors. The partition wave quantities perform well in terms of direction and frequency but the magnitude and directional spread typically have larger discrepancies. The high-frequency tail is examined through the mean...
Tipo: Text Palavras-chave: WAVEWATCH III; Spectral wave modeling; Wave hindcasting; Source terms; Higher order wave moments; Swell dissipation.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00280/39122/38300.pdf
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Emerging trends in the sea state of the Beaufort and Chukchi seas ArchiMer
Thomson, Jim; Fan, Yalin; Stammerjohn, Sharon; Stopa, Justin; Erick Rogers, W.; Girard-ardhuin, Fanny; Ardhuin, Fabrice; Shen, Hayley; Perrie, Will; Shen, Hui; Ackley, Steve; Babanin, Alex; Liu, Qingxiang; Guest, Peter; Maksym, Ted; Wadhams, Peter; Fairall, Chris; Persson, Ola; Doble, Martin; Graber, Hans; Lund, Bjoern; Squire, Vernon; Gemmrich, Johannes; Lehner, Susanne; Holt, Benjamin; Meylan, Mike; Brozena, John; Bidlot, Jean-raymond.
The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance....
Tipo: Text Palavras-chave: Sea ice; Arctic Ocean; Ocean surface waves.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00345/45590/45202.pdf
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Estimates of ocean wave heights and attenuation in sea ice using the SAR wave mode on Sentinel-1A ArchiMer
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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Estimating wave orbital velocity through the azimuth cutoff from space-borne satellites ArchiMer
Stopa, Justin; Ardhuin, Fabrice; Chapron, Bertrand; Collard, Fabrice.
It has been long accepted that ocean wave conditions recorded from synthetic aperture radar (SAR) aboard satellites resolve large scale swells. SARs make use of its displacement to achieve fine resolution; however the random surface motions can reduce its nominal azimuthal resolution. Accordingly, the SAR spectral azimuth response mirrors the probability distribution of the radial velocity component of the scatters. This effect, quantified in a measure called the azimuth cutoff, is estimated by defining a scale based on the fitting of a Gaussian function to the radar cross section azimuth spectrum. The independent measure provides additional sea state information related to the root mean square surface orbital wave velocity. We use data recorded from the...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00310/42170/41471.pdf
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Measuring currents, ice drift, and waves from space: the Sea surface KInematics Multiscale monitoring (SKIM) concept ArchiMer
Ardhuin, Fabrice; Aksenov, Yevgueny; Benetazzo, Alvise; Bertino, Laurent; Brandt, Peter; Caubet, Eric; Chapron, Bertrand; Collard, Fabrice; Cravatte, Sophie; Delouis, Jean Marc; Dias, Frederic; Dibarboure, Gerald; Gaultier, Lucile; Johannessen, Johnny; Korosov, Anton; Manucharyan, Georgy; Menemenlis, Dimitris; Menendez, Melisa; Monnier, Goulven; Mouche, Alexis; Nouguier, Frederic; Nurser, George; Rampal, Pierre; Reniers, Ad; Rodriguez, Ernesto; Stopa, Justin; Tison, Celine; Ubelmann, Clement; Van Sebille, Erik; Xie, Jiping.
We propose a satellite mission that uses a near-nadir Ka-band Doppler radar to measure surface currents, ice drift and ocean waves at spatial scales of 40 km and more, with snapshots at least every day for latitudes 75 to 82 degrees, and every few days for other latitudes. The use of incidence angles of 6 and 12 degrees allows for measurement of the directional wave spectrum, which yields accurate corrections of the wave-induced bias in the current measurements. The instrument's design, an algorithm for current vector retrieval and the expected mission performance are presented here. The instrument proposed can reveal features of tropical ocean and marginal ice zone (MIZ) dynamics that are inaccessible to other measurement systems, and providing global...
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Ano: 2018 URL: http://archimer.ifremer.fr/doc/00442/55318/56843.pdf
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Measuring ocean waves in sea ice using SAR imagery: A quasi-deterministic approach evaluated with Sentinel-1 and in situ data ArchiMer
Ardhuin, Fabrice; Stopa, Justin; Chapron, Bertrand; Collard, Fabrice; Smith, Madison; Thomson, Jim; Doble, Martin; Blomquist, Byron; Persson, Ola; Collins, Clarence O., Iii; Wadhams, Peter.
Measurements of wave heights in marginal ice zones are limited to very few in situ data. Here we revisit the linear and quasilinear theories of Synthetic Aperture Radar imaging of waves in the particular case of waves in sea ice. Instead of only working with spectra, we have developed an iterative nonlinear algorithm to estimate phase-resolved deterministic maps of wave-induced orbital velocities, from which elevation spectra can be derived. Application of this algorithm to Sentinel 1A wave mode images in the Southern Ocean shows that it produces reasonable results for swells in all directions except when they propagate at a few degrees off the range direction. The estimate of wave parameters is expected to work best when the shortest wave components,...
Tipo: Text Palavras-chave: SAR; Sentinel-1A; Ocean waves; Sea ice.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00361/47214/47451.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 the Arctic Sea State and Boundary Layer Physics Program ArchiMer
Thomson, Jim; Ackley, Stephen; Girard-ardhuin, Fanny; Ardhuin, Fabrice; Babanin, Alex; Boutin, Guillaume; Brozena, John; Cheng, Sukun; Collins, Clarence; Doble, Martin; Fairall, Chris; Guest, Peter; Gebhardt, Claus; Gemmrich, Johannes; Graber, Hans C.; Holt, Benjamin; Lehner, Susanne; Lund, Bjorn; Meylan, Michael H.; Maksym, Ted; Montiel, Fabien; Perrie, Will; Persson, Ola; Rainville, Luc; Rogers, W. Erick; Shen, Hui; Shen, Hayley; Squire, Vernon; Stammerjohn, Sharon; Stopa, Justin; Smith, Madison M.; Sutherland, Peter; Wadhams, Peter.
A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and...
Tipo: Text Palavras-chave: Arctic; Waves; Autumn; Sea ice; Beaufort; Flux.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00437/54837/56313.pdf
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Periodicity and patterns of ocean wind and wave climate ArchiMer
Stopa, Justin; Cheung, Kwok Fai.
The Climate Forecast System Reanalysis (CFSR) provides a wealth of information spanning 1979–2009 for investigation of ocean wind and wave climate. Preprocessing of the data is necessary to remove the dominant seasonal signals and to create time series of semimonthly averaged wind speed and significant wave height over a 0.5° global grid. We perform an empirical orthogonal function (EOF) analysis to extract the dominant space-time patterns. The results for the three major ocean basins show strong zonal structures in the winds and saturation of the swells corroborating prior works with various data sets. We reexamine the CFSR data in the frequency domain to identify periodic signals associated with published climate indices. The Fourier transform of the...
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Ano: 2014 URL: https://archimer.ifremer.fr/doc/00210/32149/30606.pdf
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Sea state trends and variability: consistency between models, altimeters, buoys, and seismic data (1979‐2016) ArchiMer
Stopa, Justin; Ardhuin, Fabrice; Stutzmann, Eleonore; Lecocq, Thomas.
Wave hindcasts of long time series (> 30 years) have been instrumental in understanding the wave climate. However it is still difficult to have a consistent reanalysis suitable for study of trends and inter‐annual variability. Here we explore the consistency of a wave hindcast with independent observations from moored buoys, satellite altimeters, and seismic data. We use the Climate Forecast System Reanalysis (CFSR) winds to drive a wave model since extreme events are generally well captured. Unfortunately the original CFSR winds are not homogeneous in time. We systematically modify this wind field in time and space to produce a wave field that has homogeneous differences against the Globwave/SeaStateCCI altimeter wave height database. These corrections...
Tipo: Text Palavras-chave: Wave hindcasting; COWCLIP; Seismic noise; Long-term trends; Climate Forecast System Reanalysis; Data homogeneity.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00490/60181/63522.pdf
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Significant wave heights from Sentinel-1 SAR: Validation and applications ArchiMer
Stopa, Justin; Mouche, Alexis.
Two empirical algorithms are developed for wave mode images measured from the synthetic aperture radar aboard Sentinel-1 A. The first method, called CWAVE_S1A, is an extension of previous efforts developed for ERS2 and the second method, called Fnn, uses the azimuth cutoff amongst other parameters to estimate significant wave heights and average wave periods without using a modulation transfer function. Neural networks are trained using co-located data generated from WAVEWATCH III and independently verified with data from altimeters and in-situ buoys. We use neural networks to relate the nonlinear relationships between the input SAR image parameters and output geophysical wave parameters. CWAVE_S1A performs well and has reduced precision compared to Fnn...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00363/47415/47415.pdf
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Spectral attenuation of gravity wave and model calibration in pack ice ArchiMer
Cheng, Sukun; Stopa, Justin; Ardhuin, Fabrice; Shen, Hayley H.
We investigate an instance of wave propagation in the fall of 2015 in thin pack ice (<0.3 m) and use the resulting attenuation data to calibrate two viscoelastic wave-in-ice models that describe wave evolution. The study domain is 400 km by 300 km adjacent to a marginal ice zone (MIZ) in the Beaufort Sea. From Sentinel-1A synthetic aperture radar (SAR) imagery, the ice cover is divided into two regions delineated by the first appearance of leads. According to the quality of SAR retrievals, we focus on a range of wavenumbers corresponding to 9∼15 s waves from the open water dispersion relation. By pairing directional wave spectra from different locations, we obtain wavenumber-dependent attenuation rates, which slightly increase with increasing wavenumber...
Tipo: Text Palavras-chave: Pack ice; Linear surface gravity wave; SAR derived wave spectra; Wave attenuation; Viscoelastic model calibration.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00599/71123/69427.pdf
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Strong and highly variable push of ocean waves on Southern Ocean sea ice ArchiMer
Stopa, Justin; Sutherland, Peter; Ardhuin, Fabrice.
Sea ice in the Southern Ocean has expanded over most of the past 20 y, but the decline in sea ice since 2016 has taken experts by surprise. This recent evolution highlights the poor performance of numerical models for predicting extent and thickness, which is due to our poor understanding of ice dynamics. Ocean waves are known to play an important role in ice break-up and formation. In addition, as ocean waves decay, they cause a stress that pushes the ice in the direction of wave propagation. This wave stress could not previously be quantified due to insufficient observations at large scales. Sentinel-1 synthetic aperture radars (SARs) provide high-resolution imagery from which wave height is measured year round encompassing Antarctica since 2014. Our...
Tipo: Text Palavras-chave: Wave-ice interaction; Southern Ocean marginal ice zone; Wave radiation stress; Sentinel-1 SAR; Synthetic aperture radar.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00444/55609/57255.pdf
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Swell dissipation from 10 years of Envisat ASAR in wave mode ArchiMer
Stopa, Justin; Ardhuin, Fabrice; Husson, Romain; Jiang, Haoyu; Chapron, Bertrand; Collard, Fabrice.
Swells are found in all oceans and strongly influence the wave climate and air-sea processes. The poorly known swell dissipation is the largest source of error in wave forecasts and hindcasts. We use synthetic aperture radar data to identify swell sources and trajectories, allowing a statistically significant estimation of swell dissipation. We mined the entire Envisat mission 2003–2012 to find suitable storms with swells (13 < T < 18 s) that are observed several times along their propagation. This database of swell events provides a comprehensive view of swell extending previous efforts. The analysis reveals that swell dissipation weakly correlates with the wave steepness, wind speed, orbital wave velocity, and the relative direction of wind and...
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00324/43534/43079.pdf
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Thirty-four years of Hawaii wave hindcast from downscaling of climate forecast system reanalysis ArchiMer
Li, Ning; Cheung, Kwok Fai; Stopa, Justin; Hsiao, Feng; Chen, Yi-leng; Vega, Luis; Cross, Patrick.
The complex wave climate of Hawaii includes a mix of seasonal swells and wind waves from all directions across the Pacific. Numerical hindcasting from surface winds provides essential space-time information to complement buoy and satellite observations for studies of the marine environment. We utilize WAVEWATCH III and SWAN (Simulating WAves Nearshore) in a nested grid system to model basin-wide processes as well as high-resolution wave conditions around the Hawaiian Islands from 1979 to 2013. The wind forcing includes the Climate Forecast System Reanalysis (CFSR) for the globe and downscaled regional winds from the Weather Research and Forecasting (WRF) model. Long-term in-situ buoy measurements and remotely-sensed wind speeds and wave heights allow...
Tipo: Text Palavras-chave: Swells; Wind waves; Wave hindcast; Island sheltering; Spectral wave models; Weather Research and Forecasting model.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00313/42425/42235.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
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Wave Attenuation Through an Arctic Marginal Ice Zone on 12 October 2015: 2. Numerical Modeling of Waves and Associated Ice Breakup ArchiMer
Ardhuin, Fabrice; Boutin, Guillaume; Stopa, Justin; Girard-ardhuin, Fanny; Melsheimer, Christian; Thomson, Jim; Kohout, Alison; Doble, Martin; Wadhams, Peter.
Many processes that affect ocean surface gravity waves in sea ice give rise to attenuation rates that vary with both wave frequency and amplitude. Here we particularly test the possible effects of basal friction, scattering by ice floes, and dissipation in the ice layer due to dislocations, and ice breakup by the waves. The possible influence of these processes is evaluated in the marginal ice zone of the Beaufort Sea, where extensive wave measurements were performed. The wave data includes in situ measurements and the first kilometer-scale map of wave heights provided by Sentinel-1 SAR imagery on 12 October 2015, up to 400 km into the ice. We find that viscous friction at the base of an ice layer gives a dissipation rate that may be too large near the ice...
Tipo: Text Palavras-chave: Wind-waves; Sea ice; WAVEWATCH III; SAR; Beaufort; Arctic.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00462/57372/59439.pdf
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Wave climate in the Arctic 1992-2014: seasonality and trends ArchiMer
Stopa, Justin; Ardhuin, Fabrice; Girard-ardhuin, Fanny.
Over the past decade, the diminishing Arctic sea ice has impacted the wave field, which depends on the ice-free ocean and wind. This study characterizes the wave climate in the Arctic spanning 1992–2014 from a merged altimeter data set and a wave hindcast that uses CFSR winds and ice concentrations from satellites as input. The model performs well, verified by the altimeters, and is relatively consistent for climate studies. The wave seasonality and extremes are linked to the ice coverage, wind strength, and wind direction, creating distinct features in the wind seas and swells. The altimeters and model show that the reduction of sea ice coverage causes increasing wave heights instead of the wind. However, trends are convoluted by interannual climate...
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00347/45816/45461.pdf
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