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| Registros recuperados: 13 | |
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| Bentamy, Abderrahim; Grodsky, Semyon A.; Katsaros, Kristina; Mestas-nunez, Alberto M.; Blanke, Bruno; Desbiolles, Fabien. |
| A new method is developed to estimate daily turbulent airsea fluxes over the global ocean on a 0.25 degrees grid. The required surface wind speed (w(10)) and specific air humidity (q(10)) at 10m height are both estimated from remotely sensed measurements. w(10) is obtained from the SeaWinds scatterometer on board the QuikSCAT satellite. A new empirical model relating brightness temperatures (T-b) from the Special Sensor Microwave Imager (SSM/I) and q(10) is developed. It is an extension of the author's previous q(10) model. In addition to T-b, the empirical model includes sea surface temperature (SST) and airsea temperature difference data. The calibration of the new empirical q(10) model utilizes q(10) from the latest version of the National Oceanography... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00137/24825/23575.pdf |
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| Grodsky, Semyon A.; Carton, James A.; Bentamy, Abderrahim. |
| In the presence of stable near-surface haline stratification, intermittent cold sea surface temperature (SST, upwelling) events produced by gap winds off the Central American Pacific coast should be accompanied by uplifts of saltier water. We illustrate that Aquarius satellite sea surface salinity (SSS) captures these high SSS events. In boreal winter when the intense gap winds are frequent, two tongues of anomalously salty water develop off the Gulfs of Tehuantepec and Papagayo. During that season the average SSS in the meridionally oriented Tehuantepec tongue is about 0.4 psu saltier than the background SSS. The zonally elongated Papagayo tongue stands out even more strongly, being 1-2 psu saltier than SSS in the neighbouring Panama Bight. The spatial... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00211/32184/30751.pdf |
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| 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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| Grodsky, Semyon A.; Kudryavtsev, Vladimir N.; Bentamy, Abderrahim; Carton, James A.; Chapron, Bertrand. |
| Scatterometer radar backscatter depends on the relationship linking surface stress and surface roughness. SST can alter the growth rate of centimeter-scale waves through its impact on air and water density and water viscosity. This SST-dependency has not been included in the standard Geophysical Model Functions. This study uses a radar imaging model to evaluate this SST-dependence and compares the results to observations from QuikScat Ku-band and ASCAT C-band scatterometers. A SST correction could raise wind speeds by up to 0.2 ms(-1) in the storm track region of the Southern Ocean for C-band scatterometers. For the higher frequency Ku-band scatterometers, a SST-induced reduction up to 0.4 ms(-1) is predicted south of 60(-S), where SST is cold and winds... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00088/19898/17552.pdf |
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| Grodsky, Semyon A.; Reul, Nicolas; Chapron, Bertrand; Carton, James A.; Bryan, Frank O.. |
| Sea surface salinity (SSS) from the Aquarius and SMOS satellite missions displays a steady increase of ~1psu over the entire northwestern Atlantic shelf south of Nova Scotia during the 2011-2015. Put in the context of longer ocean profile data the results suggest that mixed layer salinity and temperature north of the Gulf Stream experience positively correlated shelf-wide interannual oscillations (1psu/2degC). Salty and warm events occur coincident with anomalous easterly-southeasterly winds and Ekman transport counteracting the mean southwestward shelf currents. They are coincident with the weakening of both branches of the Scotian Shelf Current (SSC), but only moderately correlate with shifts of the Gulf Stream North Wall. This suggests that salt... |
| Tipo: Text |
Palavras-chave: Salinity; Interannual; Satellite. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00376/48736/49100.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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| Grodsky, Semyon A.; Reul, Nicolas; Vandemark, Douglas; Bentamy, Abderrahim. |
| The time variability of wind and rainfall in the Atlantic Intertropical Convergence Zone (ITCZ) has a wide oscillation spectrum that includes strong intra-month periodicities. These latter short-period oscillations span from individual convection lifecycle events of a few hours to longer pentad and multi-week convective cluster periods. This study reports on measured ITCZ rain variability at periods of a few weeks and its imprint on sea surface salinity (SSS) observed using satellite remote sensing. Despite small amplitude of variations of only 0.1−0.2 psu, these changes are shown to be detectable in radiometer SSS estimates collected by the Soil Moisture Active Passive (SMAP) satellite. They are shown to develop in the mid-Atlantic ITCZ latitude band and... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00509/62045/66197.pdf |
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| Bentamy, Abderrahim; Grodsky, Semyon A.; Chapron, Bertrand; Carton, James A.. |
| Global winds provided by satellite scatterometry are an important aspect of the ocean observing system. Many applications require well-calibrated time series of winds over time periods spanned by multiple missions. But sensors on individual satellites differ, introducing differences in wind estimates. This study focuses on global winds from two scatterometers, ERS-2 (1996-2001) and QuikSCAT (1999-2009) that show persistent differences during their period of overlap (July-1999 to January 2001). We examine a set of collocated observations during this period to evaluate the causes of these differences. The use of different operating frequencies leads to differences that depend on rain rate, wind velocity, and SST. The enhanced sensitivity to rain rate of the... |
| Tipo: Text |
Palavras-chave: Scatterometer winds; SST; Inter-instrument bias. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00139/25071/23190.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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| Bentamy, Abderrahim; Grodsky, Semyon A.; Carton, James A.; Croize-fillon, Denis; Chapron, Bertrand. |
| Surface winds from two scatterometers, the Advanced scatterometer (ASCAT), available since 2007, and QuikSCAT, which was available through November 2009, show persistent differences during their period of overlap. This study examines a set of collocated observations during a 13-month period November 2008 through November 2009, to evaluate the causes of these differences. A difference in the operating frequency of the scatterometers leads to differences that this study argues depend on rain rate, wind velocity, and SST. The impact of rainfall on the higher frequency QuikSCAT introduces biases of up to 1 m s(-1) in the tropical convergence zones and along the western boundary currents even after rain flagging is applied. This difference from ASCAT is reduced... |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00070/18126/15691.pdf |
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| Desbiolles, Fabien; Bentamy, Abderrahim; Blanke, Bruno; Roy, Claude; Mestas-nunez, Alberto M.; Grodsky, Semyon A.; Herbette, Steven; Cambon, Gildas; Maes, Christophe. |
| Surface winds (equivalent neutral wind velocities at 10 m) from scatterometer missions since 1992 have been used to build up a 20-year climate series. Optimal interpolation and kriging methods have been applied to continuously provide surface wind speed and direction estimates over the global ocean on a regular grid in space and time. The use of other data sources such as radiometer data (SSM/I) and atmospheric wind reanalyses (ERA-Interim) has allowed building a blended product available at 1/4° spatial resolution and every 6 hours from 1992 to 2012. Sampling issues throughout the different missions (ERS-1, ERS-2, QuikSCAT, and ASCAT) and their possible impact on the homogeneity of the gridded product are discussed. In addition, we assess carefully the... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00366/47686/47725.pdf |
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| Registros recuperados: 13 | |
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