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| Registros recuperados: 58 | |
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| Reul, Nicolas; Chapron, Bertrand. |
| [1] Foam formations at the sea surface significantly contribute to microwave brightness temperature signatures over the ocean for moderate to high wind speeds. The thickness of foam layers generated by breaking waves follows a specific distribution due to unsteadiness of breaking and the large range of wave scales involved in the phenomenon. Although the effect of a distributed thickness-parameter on the foam-induced microwave brightness temperature may be comparable to or larger than the fractional whitecap coverage, it is not yet included in brightness models. To fill this gap, we develop a dynamical model for the conditional fraction of sea-surface covered by whitecaps with given thickness, as a function of wind speed. It is an integrated function of... |
| Tipo: Text |
Palavras-chave: Sea foam; Breaking waves; Thickness; Fractional coverage; Microwave brightness temperature. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/00000/10693/9320.pdf |
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| Reul, Nicolas; Chapron, Bertrand; Zabolotskikh, E.; Donlon, C.; Mouche, Alexis; Tenerelli, Joseph; Collard, F.; Piolle, Jean-francois; Fore, A.; Yueh, S.; Cotton, J.; Francis, P.; Quilfen, Yves; Kudryavtsev, V.. |
| Combined microwave brightness temperature measurements from recent L- and dual C-band satellite radiometers provide new estimates of surface wind speed structure in Tropical Cyclones which enhances temporal sampling capability for gale (34-knots), damaging (50-knots) and destructive (64-knots) wind radii. Wind radii estimates in Tropical Cyclones (TC) are crucial to help determine the TC wind structure for the production of effective warnings and to constrain initial conditions for a number of applications. In that context, we report on the capabilities of a new generation of satellite microwave radiometers operating at L-band frequency (~1.4 GHz) and dual C-band (~6.9 and 7.3 GHz). These radiometers provide wide swath (> 1000 km) coverage at a spatial... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00376/48758/49151.pdf |
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| Reul, Nicolas; Chapron, Bertrand; Zabolotskikh, E.; Donlon, C.; Quilfen, Yves; Guimbard, Sebastien; Piolle, Jean-francois. |
| Five years of SMOS L-band brightness temperature data intercepting a large number of tropical cyclones (TCs) are analyzed. The storm-induced half-power radio-brightness contrast (ΔI) is defined as the difference between the brightness observed at a specific wind force and that for a smooth water surface with the same physical parameters. ΔI can be related to surface wind speed and has been estimated for ~ 300 TCs that intercept with SMOS measurements. ΔI, expressed in a common storm-centric coordinate system, shows that mean brightness contrast monotonically increases with increased storm intensity ranging from ~ 5 K for strong storms to ~ 24 K for the most intense Category 5 TCs. A remarkable feature of the 2D mean ΔI fields and their variability is that... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00324/43542/43178.pdf |
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| Tournadre, Jean; Chapron, Bertrand; Reul, Nicolas; Vandemark, D. |
| [1] About 5% of Ku-band altimeter ocean data are degraded by the occurrence of high radar return cross sections (sigma(0)), usually called sigma(0) blooms. During blooms, which occur during no or low wind conditions, the mean altimeter waveform can significantly depart from the expected shape. In about 60% of the cases the waveforms are distorted to such an extent that either the range tracker loses lock or the off-nadir angle estimate becomes unrealistic. The analysis of high data rate altimeter waveforms during bloom events reveals the presence of V-shaped patterns similar to the ones observed during rain events. These patterns trace small-scale (i.e., smaller than the altimeter footprint) changes in surface backscatter. Such variations of surface... |
| Tipo: Text |
Palavras-chave: Slick; Sigma blooms; Altimeter waveforms. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1353.pdf |
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| Mouche, Alexis; Chapron, Bertrand; Reul, Nicolas. |
| The normalized radar cross-section ( NRCS) expression of the Local Curvature Approximation (LCA-1) is derived to first order. The polarization sensitivity of this model is compared to the Kirchhoff Approximation ( KA), Two-Scale Model (TSM), Small Slope Approximation (SSA-1) and Small Perturbation Method (SPM-1) to first order in the backscattering configuration. Analytical comparisons and numerical simulations show that LCA-1 and TSM could be rewritten with the same formulation and that their polarization sensitivities are comparable. Comparisons with experimental data acquired in C- and Ku-band reveal that the polarization sensitivities of these models are not adequate. However, the NRCS azimuth modulation predicted by LCA-1 is found to be dependent on... |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3001.pdf |
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| 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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| Cotton, J.; Francis, P.; Heming, J.; Forsythe, M.; Reul, Nicolas; Donlon, C.. |
| A new generation of L-band sensors, such as ESA's Soil Moisture Ocean Salinity (SMOS) mission, have the capability to provide information on the ocean-surface wind speed under high wind and rain conditions. In this study we evaluate the use of SMOS wind speeds within Met Office numerical weather prediction (NWP). Observation minus model background (O-B) departure statistics are used to investigate SMOS error characteristics, quality flags, and develop a quality control method. Observation errors and spatial correlation distances are estimated using a statistical method. Observing system experiments are performed to diagnose the impact of SMOS on NWP forecasts and analyses, including tropical cyclone (TC) predictions. The quality of SMOS retrievals appears... |
| Tipo: Text |
Palavras-chave: SMOS; L-band wind speed; Data assimilation; Tropical cyclones; NWP. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00417/52868/53782.pdf |
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| Boutin, Jacqueline; Vergely, Jean-luc; Dinnat, Emmanuel P.; Waldteufel, Philippe; D'Amico, Francesco; Reul, Nicolas; Supply, Alexandre; Thouvenin-masson, Clovis. |
| Earlier studies have pointed out systematic differences between sea surface salinity retrieved from L-band radiometric measurements and measured in situ, which depend on sea surface temperature (SST). We investigate how to cope with these differences given existing physically based radiative transfer models. In order to study differences coming from seawater dielectric constant parametrization, we consider the model of Somaraju and Trumpf (2006) (ST) which is built on sound physical bases and close to a single relaxation term Debye equation. While ST model uses fewer empirically adjusted parameters than other dielectric constant models currently used in salinity retrievals, ST dielectric constants are found close to those obtained using the Meissner and... |
| Tipo: Text |
Palavras-chave: Dielectric constant; L-band microwave radiometry; Sea surface salinity (SSS).. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00657/76943/78203.pdf |
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| Reul, Nicolas; Saux Picart, Stephane; Chapron, Bertrand; Vandemark, D.; Tournadre, Jean; Salisbury, J.. |
| Microwave Sea Surface Salinity (SSS) measurements can be performed by isolating the emissivity response to salinity changes from numerous geophysical effects, including surface temperature and wind waves. At L-band frequencies (1 to 2 GHz), the sensitivity to SSS is sufficient but it falls off quickly as frequency is increased. Nevertheless, methods using higher microwave frequencies with much lower SSS sensitivity than at L band, can already be tested. In particular, combining 6 and 10 GHz data in vertical polarization efficiently minimizes sea surface roughness and thermal impacts. Using AMSR-E data, the retrieved bi-monthly maps of SSS at 0.5 degrees resolution over the region of the Amazon plume show relative accuracy in-line with the future L-band... |
| Tipo: Text |
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| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6620.pdf |
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| Tenerelli, Joseph; Reul, Nicolas; Mouche, Alexis; Chapron, Bertrand. |
| The "galactic glitter" phenomenon at L-band, i.e., the scattering of celestial sky radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident... |
| Tipo: Text |
Palavras-chave: Scattering; Remote sensing; Radiometry. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3922.pdf |
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| Reul, Nicolas; Tenerelli, Joseph; Floury, N; Chapron, Bertrand. |
| We examine how the rough sea surface scattering of L-band celestial sky radiation might affect the measurements of the future European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. For this purpose, we combined data from several surveys to build a comprehensive all-sky L-band celestial sky brightness temperature map for the SMOS mission that includes the continuum radiation and the hydrogen line emission rescaled for the SMOS bandwidth. We also constructed a separate map of strong and very localized sources that may exhibit L-band brightness temperatures exceeding 1000 K. Scattering by the roughened ocean surface of radiation from even the strongest localized sources is found to reduce the contributions from these localized strong sources... |
| Tipo: Text |
Palavras-chave: Sea surface electromagnetic scattering; Microwave radiometry. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3636.pdf |
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| Grodsky, Semyon A.; Reul, Nicolas; Bentamy, Abderrahim; Vandemark, Douglas; Guimbard, Sebastien. |
| One of the saltiest seas, the Mediterranean, experiences significant salinity variations in near surface layers. Satellite sea surface salinity (SSS) data obtained using Soil Moisture Active Passive (SMAP) mission indicate steady salinification of the eastern Mediterranean Levantine Basin at a rate of ~0.14 psu/year during 2015–2018. Satellite-observed salinity changes are confirmed by Argo float data and suggest possible changes in properties of the Levantine Intermediate Water. Eastern Mediterranean salinification often coincides with a freshening of the western Ionian Sea. Based on satellite altimetry geostrophic currents, these salinity changes are concurrent with a weakening cyclonic circulation in the Levantine Basin and strengthening anticyclonic... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00503/61430/65113.pdf |
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| Boutin, J.; Martin, N.; Yin, X.; Reul, Nicolas; Spurgeon, P.. |
| We validate Soil Moisture and Ocean Salinity (SMOS) sea surface salinity (SSS) retrieved during August 2010 from the European Space Agency SMOS processing. Biases appear close to land and ice and between ascending and descending orbits; they are linked to image reconstruction issues and instrument calibration and remain under study. We validate the SMOS SSS in conditions where these biases appear to be small. We compare SMOS and ARGO SSS over four regions far from land and ice using only ascending orbits. Four modelings of the impact of the wind on the sea surface emissivity have been tested. Results suggest that the L-band brightness temperature is not linearly related to the wind speed at high winds as expected in the presence of emissive foam, but that... |
| Tipo: Text |
Palavras-chave: L-Band; Microwave Radiometry; Ocean Salinity; Sea Surface. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00074/18557/16108.pdf |
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| Grodsky, Semyon A.; Reul, Nicolas; Lagerloef, Gary; Reverdin, Gilles; Carton, James A.; Chapron, Bertrand; Quilfen, Yves; Kudryavtsev, Vladimir N.; Kao, Hsun-ying. |
| At its seasonal peak the Amazon/Orinoco plume covers a region of 10^6 km2 in the western tropical Atlantic with more than 1m of extra freshwater, creating a near-surface barrier layer (BL) that inhibits mixing and warms the sea surface temperature (SST) to >29oC. Here new sea surface salinity (SSS) observations from the Aquarius/SACD and SMOS satellites help elucidate the ocean response to hurricane Katia, which crossed the plume in early fall, 2011. Its passage left a 1.5psu high haline wake covering >10^5 km2 (in its impact on density, the equivalent of a 3.5oC cooling) due to mixing of the shallow BL. Destruction of this BL apparently decreased SST cooling in the plume, and thus preserved higher SST and evaporation than outside. Combined with SST,... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00094/20540/18943.pdf |
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| Salisbury, Joseph; Vandemark, Douglas; Joensson, Bror; Balch, William; Chakraborty, Sumit; Lohrenz, Steven; Chapron, Bertrand; Hales, Burke; Mannino, Antonio; Mathis, Jeremy T.; Reul, Nicolas; Signorini, Sergio R.; Wanninkhof, Rik; Yates, Kimberly K.. |
| Space-based observations offer unique capabilities for studying spatial and temporal dynamics of the upper ocean inorganic carbon cycle and, in turn, supporting research tied to ocean acidification (OA). Satellite sensors measuring sea surface temperature, color, salinity, wind, waves, currents, and sea level enable a fuller understanding of a range of physical, chemical, and biological phenomena that drive regional OA dynamics as well as the potentially varied impacts of carbon cycle change on a broad range of ecosystems. Here, we update and expand on previous work that addresses the benefits of space-based assets for OA and carbonate system studies. Carbonate chemistry and the key processes controlling surface ocean OA variability are reviewed. Synthesis... |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00271/38234/36417.pdf |
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| Sabia, Roberto; Camps, A; Vall Ilossera, M; Reul, Nicolas. |
| Aiming to provide sea surface salinity (SSS) maps with a spatiotemporal averaged accuracy of 0.1 psu (practical salinity units), the Soil Moisture and Ocean Salinity (SMOS) community is increasingly focusing on the determination of a robust inversion scheme to enable SSS retrieval from L-band brightness temperature data. In the framework of the Synergetic Aspects and Auxiliary Data Concepts for Sea Surface Salinity Measurements from Space project, efforts have been oriented toward a quantitative analysis of SSS retrieval using different auxiliary data sets. This paper aims to contribute to the assessment of the SMOS salinity retrieval error budget in view of the upcoming SMOS mission ground segment development. Aiming to do that, different models and... |
| Tipo: Text |
Palavras-chave: Spatiotemporal averaging; Sea salinity; Microwave radiometry; Auxiliary data. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2011.pdf |
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| Registros recuperados: 58 | |
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