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Registros recuperados: 15
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A simplified model for the baroclinic and barotropic ocean response to moving tropical cyclones: 1. Satellite Observations ArchiMer
Kudryavtsev, Vladimir; Monzikova, Anna; Combot, Clement; Chapron, Bertrand; Reul, Nicolas; Quilfen, Yves.
Changes of sea surface temperature (SST) and height (SSH) derived from 20‐days passive microwave and altimeter measurements for three tropical cyclones (TCs), Jimena, Ignacio and Kilo, during the 2015 Pacific hurricane season, sampling different stages of intensification, wind speeds, radii, Coriolis parameter, translation velocities, and ocean stratification conditions, are reported and analyzed. As triggered along the path of moving TCs, very large interior ocean displacements can occur to leave prominent SSH anomalies in the TC wake. Resulting surface depressions can reach.3‐.5 m, depending upon size, translation speed, and ocean stratification conditions. These signatures can be quite persistent, i.e. more than few weeks, to possibly be intercepted...
Tipo: Text Palavras-chave: Tropical cyclones; Surface temperature anomalies; Surface height anomalies.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00491/60252/63653.pdf
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A simplified model for the baroclinic and barotropic ocean response to moving tropical cyclones: 2. Model and Simulations ArchiMer
Kudryavtsev, Vladimir; Monzikova, Anna; Combot, Clement; Chapron, Bertrand; Reul, Nicolas.
A simplified analytical model is developed to describe the baroclinic and barotropic ocean response to moving Tropical cyclones (TC) and their associated pycnocline erosions. The model builds on classical mixed layer (ML) models and linear models of ocean response to transient events. As suggested, disturbances of the upper ocean stratification caused by the ML development shall not strongly impact the dynamics of baroclinic modes. Accordingly, the baroclinic response can be estimated using the pre‐storm ocean stratification condition. To the contrary, the ML is strongly coupled with these interior motions, through the TC‐induced upwelling response which affects the entrainment velocity. The ML temperature is then strongly dependent on the local...
Tipo: Text Palavras-chave: Tropical cyclones; Simplified mode of ocean response; Simulation of satellite observations.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00491/60251/63652.pdf
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A simplified wave enhancement criterion for moving extreme events ArchiMer
Kudryavtsev, Vladimir; Golubkin, Pavel; Chapron, Bertrand.
An analytical model is derived to efficiently describe the wave energy distribution along the main transects of a moving extreme weather event. The model essentially builds on a generalization of the self-similar wave growth model and the assumption of a strongly dominant single spectral mode in a given quadrant of the storm. The criterion to anticipate wave enhancement with the generation of trapped abnormal waves defined as inline image, with inline image, inline image, and inline image, radial distance, average sustained wind speed, and translation velocity, respectively. Constants inline image and inline image follow the fetch-law definitions. If forced during a sufficient time scale interval, also defined from this generalized self-similar wave growth...
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Ano: 2015 URL: http://archimer.ifremer.fr/doc/00295/40644/39603.pdf
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Imaging mesoscale upper ocean dynamics using synthetic aperture radar and optical data ArchiMer
Kudryavtsev, Vladimir; Myasoedov, Alexander; Chapron, Bertrand; Johannessen, Johnny A.; Collard, Fabrice.
A synergetic approach for quantitative analysis of high-resolution ocean synthetic aperture radar (SAR) and imaging spectrometer data, including the infrared (IR) channels, is suggested. This approach first clearly demonstrates that sea surface roughness anomalies derived from Sun glitter imagery compare very well to SAR roughness anomalies. As further revealed using these fine-resolution (similar to 1 km) observations, the derived roughness anomaly fields are spatially correlated with sharp gradients of the sea surface temperature (SST) field. To quantitatively interpret SAR and optical (in visible and IR ranges) images, equations are derived to relate the "surface roughness" signatures to the upper ocean flow characteristics. As developed, a direct link...
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Ano: 2012 URL: https://archimer.ifremer.fr/doc/00079/18999/16570.pdf
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Joint sun-glitter and radar imagery of surface slicks ArchiMer
Kudryavtsev, Vladimir; Myasoedov, Alexander; Chapron, Bertrand; Johannessen, Johnny A.; Collard, Fabrice.
A method is proposed to retrieve and interpret fine spatial variations of the sea surface roughness in sun glitter imagery. Observed sun glitter brightness anomalies are converted using a transfer function determined from the smoothed shape of sun glitter brightness. The method is applied to MODIS and MERIS sun glitter imagery of natural oil seeps and the catastrophic Deepwater Horizon oil spill in the Gulf of Mexico. The short-scale roughness variations in the presence of mineral oils slicks are consistently extracted and compared to variations associated with the biogenic slicks. In doing so, the wind speed dependency on the roughness anomalies is also considered. A comparison to normalized radar cross section (NRCS) anomalies taken from the...
Tipo: Text Palavras-chave: Sun-glitter; Mean square slope; Surface slicks; Oil spills; SAR imaging model; SAR and optical synergy.
Ano: 2012 URL: https://archimer.ifremer.fr/doc/00083/19439/17217.pdf
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Multisensor observations of the Amazon-Orinoco river plume interactions with hurricanes ArchiMer
Reul, Nicolas; Quilfen, Yves; Chapron, Bertrand; Fournier, Severine; Kudryavtsev, Vladimir; Sabia, Roberto.
An analysis is presented for the spatial and intensity distributions of North Atlantic extreme atmospheric events crossing the buoyant Amazon-Orinoco freshwater plume. The sea surface cooling amplitude in the wake of an ensemble of storm tracks traveling in that region is estimated from satellite products for the period 1998-2012. For the most intense storms, cooling is systematically reduced by approximate to 50% over the plume area compared to surroundings open-ocean waters. Historical salinity and temperature observations from in situ profiles indicate that salt-driven vertical stratification, enhanced oceanic heat content, and barrier-layer presence within the plume waters are likely key oceanic factors to explain these results. Satellite SMOS surface...
Tipo: Text Palavras-chave: Hurricanes; Amazon-Orinocco river plume; SMOS SSS; Cooling inhibition; Barrier-layer; Haline stratification.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00252/36326/34855.pdf
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On C-Band Quad-Polarized Synthetic Aperture Radar Properties of Ocean Surface Currents ArchiMer
Fan, Shengren; Kudryavtsev, Vladimir; Zhang, Biao; Perrie, William; Chapron, Bertrand; Mouche, Alexis.
We present new results for ocean surface current signatures in dual co- and cross-polarized synthetic aperture radar (SAR) images. C-band RADARSAT-2 quad-polarized SAR ocean scenes are decomposed into resonant Bragg scattering from regular (non-breaking) surface waves and scattering from breaking waves. Surface current signatures in dual co- and cross-polarized SAR images are confirmed to be governed by the modulations due to wave breaking. Due to their small relaxation scale, short Bragg waves are almost insensitive to surface currents. Remarkably, the contrast in sensitivity of the non-polarized contribution to dual co-polarized signals is found to largely exceed, by a factor of about 3, the contrast in sensitivity of the corresponding cross-polarized...
Tipo: Text Palavras-chave: Quad-polarized SAR; Ocean surface current; Polarization decomposition; Bragg scattering; Breaking waves.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00588/70030/67948.pdf
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On Growth Rate of Wind Waves: Impact of Short-Scale Breaking Modulations ArchiMer
Kudryavtsev, Vladimir; Chapron, Bertrand.
The wave generation model based on the rapid distortion concept significantly underestimates empirical values of the wave growth rate. As suggested before, inclusion of the aerodynamic roughness modulations effect on the amplitude of the slope-correlated surface pressure could potentially reconcile this model approach with observations. This study explores the role of short-scale breaking modulations to amplify the growth rate of modulating longer waves. As developed, airflow separations from modulated breaking waves result in strong modulations of the turbulent stress in the inner region of the modulating waves. In turn, this leads to amplifying the slope-correlated surface pressure anomalies. As evaluated, such a mechanism can be very efficient for...
Tipo: Text Palavras-chave: Atm; Ocean Structure; Phenomena; Atmosphere-ocean interaction.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00313/42414/41759.pdf
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Quad-polarization SAR features of ocean currents ArchiMer
Kudryavtsev, Vladimir; Kozlov, I.; Chapron, Bertrand; Johannessen, J. A..
A methodology is demonstrated to exploit the polarization sensitivity of high-resolution radar measurements to interpret and quantify upper ocean dynamics. This study particularly illustrates the potential of quad-polarization synthetic aperture radar (SAR) measurements. The analysis relies on essential characteristics of the electromagnetic scattering mechanisms and hydrodynamical principles. As the relaxation scale of centimeter-scale ocean surface scatters is typically small, radar signal anomalies associated with surface manifestations of the upper ocean dynamics on spatial scales exceeding 100 m are mostly dominated by nonresonant and nonpolarized scatters. These “scalar” contributions can thus efficiently trace local breaking and near-breaking areas,...
Tipo: Text Palavras-chave: Quad-polarized SAR; SAR imaging of ocean current; Radar scattering; Wave-current interaction; Wave breaking.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00210/32152/30611.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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SEASTAR: A Mission to Study Ocean Submesoscale Dynamics and Small-Scale Atmosphere-Ocean Processes in Coastal, Shelf and Polar Seas ArchiMer
Gommenginger, Christine; Chapron, Bertrand; Hogg, Andy; Buckingham, Christian; Fox-kemper, Baylor; Eriksson, Leif; Soulat, Francois; Ubelmann, Clément; Ocampo-torres, Francisco; Nardelli, Bruno Buongiorno; Griffin, David; Lopez-dekker, Paco; Knudsen, Per; Andersen, Ole; Stenseng, Lars; Stapleton, Neil; Perrie, William; Violante-carvalho, Nelson; Schulz-stellenfleth, Johannes; Woolf, David; Isern-fontanet, Jordi; Ardhuin, Fabrice; Klein, Patrice; Mouche, Alexis; Pascual, Ananda; Capet, Xavier; Hauser, Daniele; Stoffelen, Ad; Morrow, Rosemary; Aouf, Lotfi; Breivik, Øyvind; Fu, Lee-lueng; Johannessen, Johnny A.; Aksenov, Yevgeny; Bricheno, Lucy; Hirschi, Joel; Martin, Adrien Ch; Martin, Adiran P; Nurser, George; Polton, Jeff; Wolf, Judith; Johnsen, Harald; Soloviev, Alexander; Jacobs, Gregg A.; Collard, Fabrice; Groom, Steve; Kudryavtsev, Vladimir; Wilkin, John; Navarro, Victor; Babanin, Alex; Martin, Matthew; Siddorn, John; Saulter, Andrew; Rippeth, Tom; Emery, Bill; Maximenko, Nikolai; Romeiser, Roland; Graber, Hans; Azcarate, Aida Alvera; Hughes, Chris W.; Vandemark, Doug; Silva, Jose Da; Leeuwen, Peter Jan Van; Naveira-garabato, Alberto; Gemmrich, Johannes; Mahadevan, Amala; Marquez, Jose; Munro, Yvonne; Doody, Sam; Burbidge, Geoff.
High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean mixing and ocean vertical transports, with advanced numerical models and in situ observations highlighting fundamental changes in dynamics when scales reach 1 km. Numerous scientific publications highlight the global impact of small oceanic scales on marine ecosystems, operational forecasts and long-term climate projections through strong ageostrophic circulations, large vertical ocean velocities and mixed layer...
Tipo: Text Palavras-chave: Satellite; Air sea interactions; Upper ocean dynamics; Submesoscale; Coastal; Marginal ice zone; Radar; Along-track interferometry.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00510/62121/66325.pdf
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Sun glitter imagery of ocean surface waves. Part 1: Directional spectrum retrieval and validation ArchiMer
Kudryavtsev, Vladimir; Yurovskaya, Maria; Chapron, Bertrand; Collard, Fabrice; Donlon, Craig.
A practical method is suggested to quantitatively retrieve directional spectra of ocean surface waves from high-resolution satellite sun glitter imagery (SSGI). The method builds on direct determination of the imaging transfer function from the large-scale smoothed shape of sun glitter. Observed brightness modulations are then converted into sea surface elevations to perform directional spectral analysis. The method is applied to the Copernicus Sentinel-2 Multi-Spectral Instrument (MSI) measurements. Owing to the specific instrumental configuration of MSI (which has a primary mission dedicated to mapping of land surfaces), a physical angular difference between channel detectors on the instrument focal plane array can be used to efficiently determine the...
Tipo: Text Palavras-chave: Satellite sun glitter imagery; Ocean surface waves; 2-D spectra retrieval.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00381/49280/49678.pdf
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Sun glitter imagery of surface waves. Part 2: Waves transformation on ocean currents ArchiMer
Kudryavtsev, Vladimir; Yurovskaya, Maria; Chapron, Bertrand; Collard, Fabrice; Donlon, Craig.
Under favorable imaging conditions, the Sentinel-2 Multi-Spectral Instrument (MSI) can provide spectacular and novel quantitative ocean surface wave directional measurements in satellite Sun Glitter Imagery (SSGI). Owing to a relatively large-swath with high-spatial resolution (10 m), ocean surface roughness mapping capabilities, changes in ocean wave energy, and propagation direction can be precisely quantified at very high resolution, across spatial distances of 10 km and more. This provides unique opportunities to study ocean wave refraction induced by spatial varying surface currents. As expected and demonstrated over the Grand Agulhas current area, the mesoscale variability of near-surface currents, documented and reconstructed from satellite...
Tipo: Text Palavras-chave: Satellite Sun Glitter Imagery; Ocean surface waves; Waves transformation on the currents.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00381/49281/49677.pdf
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Wave Breaking in Slicks: Impacts on C-Band Quad-Polarized SAR Measurements ArchiMer
Wergeland, Morten; Kudryavtsev, Vladimir; Chapron, Bertrand; Brekke, Camilla; Johannessen, Johnny A..
Radarsat-2 C-band quad-polarization SAR observations of crude oil, emulsion, and plant oil slicks acquired in the wind speed range from 4 to 8 m/s and incidence angles from 30 degrees to 50 degrees are analyzed to yield new insights into the attenuation of short waves and breaking waves by surface slicks in real conditions. To provide a direct quantitative assessment of the surface wave damping, the measurements are decomposed into polarization difference (PD), polarization ratio (PR), nonpolarized (NP), and cross-polarized (CP) components. The PD signals relate to the extent of Bragg damping in the slick areas, over which the PR is systematically higher than over the ambient sea surface. Attenuation of the breaking waves is revealed to affect both the CP...
Tipo: Text Palavras-chave: Oil pollution; Radar imaging; Sea surface; Surface waves.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00363/47460/47484.pdf
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Wave spectrum retrieval from airborne sunglitter images ArchiMer
Yurovskaya, Maria; Rascle, Nicolas; Kudryavtsev, Vladimir; Chapron, Bertrand; Marie, Louis; Molemaker, Jeroen.
Reconstruction and evolution of two-dimensional spectra of surface waves in the Gulf of Mexico are derived from airborne sun-glitter imagery. As the proposed method is based on a linear transfer function deduced from the shape of the sunglitter brightness, the absolute wavenumber elevation spectrum does not require any additional assumption or information about sky brightness, wind or wave energy. The detailed description of the airborne image processing method is given. As demonstrated, retrieved spectra agree well with nearby NDBC buoy data, both for spectrum shape, level and energy angular distribution. The 180-degree wave direction ambiguity, inherent to image-derived spectra, is eliminated by using cross-correlation analysis between two consecutive...
Tipo: Text Palavras-chave: Sunglitter; Sea surface waves; Directional wave spectrum; Aerial photography; Field measurements; Remote sensing observations; High resolution; Drone.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00465/57712/60174.pdf
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