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| Registros recuperados: 40 | |
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| Flament, Pierre; Lumpkin, Rick; Tournadre, Jean; Armi, Laurence. |
| Observations of the downstream evolution of an oceanic zonal horizontal shear flow at a Reynolds number of about 10(11), formed as the westward North Equatorial Current passes the island of Hawai'i, reveal finite-amplitude anticyclonic vortices resulting from instability of the shear. The initial orbital period of the vortices is exactly one pendulum day (3.1 days at this latitude), centrifugal instability presumably inhibiting stronger vortices from forming. As they move downstream, they appear to pair and merge into successively larger vortices, in a geometric sequence of longer orbital periods; three subharmonic transitions are suggested with final orbital periods near 6, 12 and 24 days. |
| Tipo: Text |
Palavras-chave: Vortex; Oceanic shear flow. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/2001/publication-644.pdf |
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| Legrand, P; Schrama, Ejo; Tournadre, Jean. |
| The mean dynamic topography of the surface of the ocean is estimated using a finite difference inverse model of the ocean circulation constrained by a prior TOPEX/Poseidon-EGM96 estimate and an ocean density climatology. The EGM96 geoid uncertainties are represented by their full covariance matrix. The model finds a solution that yields a new 1°-resolution dynamic topography estimate with a 5 cm precision. The existence of this solution suggests that the uncertainties in EGM96, despite being much smaller than in previous geopotential models, are nonetheless realistic. The geodetic information constrains the inverse estimate of the ocean circulation, particularly at high latitudes. |
| Tipo: Text |
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| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/2003/publication-361.pdf |
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| Combot, Clement; Quilfen, Yves; Mouche, Alexis; Gourrion, Jerome; De Boyer Montegut, Clement; Chapron, Bertrand; Tournadre, Jean. |
| In this section, a new focus is given on the ocean response induced by Tropical Cyclones. Tropical Cyclones are among the most devastating and destructive natural hazards. Unfortunately, predicting the intensity and evolution of such individual event is still extremely difficult, owing to various internal and environmental factors, including interactions with the ocean interior. In that context, multiple satellite remote sensing observations are essential, and today, combined with denser ARGO interior measurements, the upper ocean responses to moving tropical cyclones can be more efficiently captured and monitored. |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00655/76663/77809.pdf |
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| Tran, N; Tournadre, Jean; Femenias, P. |
| This letter provides validation results on both Envisat altimeter rain detection flag and rain rate estimates. This assessment was performed based on 18-month collocated data sets between Envisat with two sensor measurements from the Tropical Rainfall Measuring Mission, i.e., the microwave imager and the precipitation radar. Along with the comparison between closest sensor measurements with strict spatial and temporal criteria, discussion is also provided on environmental context insight when interpreting comparison results based on collocated data. |
| Tipo: Text |
Palavras-chave: Remote sensing; Rain; Radar cross sections; Altimetry. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4719.pdf |
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| Tournadre, Jean. |
| New rain flags based on the dual frequency capabilities of the new Jason Poseidon-2 and Envisat RA2 altimeters have been tested, developed and adopted for the operational processing of the altimeter data. Their validation conducted during the calibration/validation phases of the satellites is presented here. The Jason flag is validated by comparison with the TOPEX one, using the Tandem mission. The results show a very good agreement between the two sensors and the two rain flags The Envisat flag is validated by comparison with both Jason and TOPEX using global and collocated data sets. The results show similar performances for the three sensors. The f relations estimated during the calibration-validation period and presented here have been given to the... |
| Tipo: Text |
Palavras-chave: Dual Frequency; Rain Flag; Altimeters; Envisat; Jason. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-419.pdf |
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| Verron, Jacques; Bonnefond, Pascal; Aouf, Lofti; Birol, Florence; Bhowmick, Suchandra A.; Calmant, Stephane; Conchy, Taina; Cretaux, Jean-francois; Dibarboure, Gerald; Dubey, A. K.; Faugere, Yannice; Guerreiro, Kevin; Gupta, P. K.; Hamon, Mathieu; Jebri, Fatma; Kumar, Raj; Morrow, Rosemary; Pascual, Ananda; Pujol, Marie-isabelle; Remy, Elisabeth; Remy, Frederique; Smith, Walter H. F.; Tournadre, Jean; Vergara, Oscar. |
| The India-France SARAL/AltiKa mission is the first Ka-band altimetric mission dedicated primarily to oceanography. The mission objectives were firstly the observation of the oceanic mesoscales but also global and regional sea level monitoring, including the coastal zone, data assimilation, and operational oceanography. SARAL/AltiKa proved also to be a great opportunity for inland waters applications, for observing ice sheet or icebergs, as well as for geodetic investigations. The mission ended its nominal phase after three years in orbit and began a new phase (drifting orbit) in July 2016. The objective of this paper is to highlight some of the most remarkable achievements of the SARAL/AltiKa mission in terms of scientific applications. Compared to the... |
| Tipo: Text |
Palavras-chave: Altimetry; Ka-band; Oceanography; Hydrology; Ice; Geodesy. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00600/71248/69623.pdf |
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| Ardhuin, Fabrice; Tournadre, Jean; Queffeulou, Pierre; Ardhuin, Fanny; Collard, Fabrice. |
| The variability of small-size iceberg distributions is revealed from a novel analysis of satellite altimeter data. A strong annual cycle is modulated by pulse-like events confined to single ocean basins, with dense iceberg populations in the South Atlantic in 2004-2005, and in the South Pacific in 2008. Anomalies in sea surface temperatures of the order of 1 degrees C may be related to the iceberg distribution. Icebergs also appear very strongly associated with anomalies in the heights of ocean waves. A preliminary parameterization of wave blocking by icebergs significantly reduces wave model errors in the region south of 45 degrees South, and has a perceptible influence on all the west coasts of the Southern hemisphere. (C) 2011 Elsevier Ltd. All rights... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00044/15535/13317.pdf |
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| Tournadre, Jean; Poisson, J. C.; Steunou, N.; Picard, B.. |
| The major drawback of Ka band, operating frequency of the AltiKa altimeter on board SARAL, is its sensitivity to atmospheric liquid water. Even light rain or heavy clouds can strongly attenuate the signal and distort the signal leading to erroneous geophysical parameters estimates. A good detection of the samples affected by atmospheric liquid water is crucial. As AltiKa operates at a single frequency, a new technique based on the detection by a Matching Pursuit algorithm of short scale variations of the slope of the echo waveform plateau has been developed and implemented prelaunch in the ground segment. As the parameterization of the detection algorithm was defined using Jason-1 data, the parameters were re-estimated during the cal-val phase, during... |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00286/39674/41519.pdf |
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| Tournadre, Jean. |
| Marine ecosystems are under increasing anthropogenic pressures from marine and terrestrial activities. Ship traffic, the major cause of change in the open ocean, and its temporal evolution are still largely unknown because of lack of data. Altimeter data provide a new powerful tool to detect and monitor the ship traffic through a method of analysis of echo waveform. The archive of seven altimeter missions has been processed to create a two decade database of ship locations. The estimated annual density maps compare well with the ones obtained from Automatic Identification System. The ship traffic analysis shows a global fourfold growth between 1992 and 2012, the largest increase being observed in the Indian Ocean and the Chinese seas reflecting the world... |
| Tipo: Text |
Palavras-chave: Altimetry; Ship traffic; Pollution; Anthropogenic pressure. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00229/34039/32432.pdf |
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| Tandeo, Pierre; Autret, Emmanuelle; Piolle, Jean-francois; Tournadre, Jean; Ailliot, Pierre. |
| The Advanced Along-Track Scanning Radiometer (AATSR) onboard Envisat is designed to provide very accurate measurements of sea surface temperature (SST). Using colocated in situ drifting buoys, a dynamical matchup database (MDB) is used to assess the AATSR-derived SST products more precisely. SST biases are then computed. Currently, Medspiration AATSR SST biases are discrete values and can introduce artificial discontinuities in AATSR level-2 SST fields. The new AATSR SST biases presented in this letter are continuous. They are computed, for nighttime and best proximity confidence data, by linear regression with different MDB covariables (wind speed, latitude, aerosol optical depth, etc.). As found, the difference between dual-view and nadir-only SST... |
| Tipo: Text |
Palavras-chave: Validation; Sea surface temperature (SST); Remote sensing; Advanced Along Track Scanning Radiometer (AATSR). |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6135.pdf |
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| Quilfen, Yves; Tournadre, Jean; Chapron, Bertrand. |
| [1] Extreme weather events such as tropical cyclones are difficult to observe with conventional means. Satellite-based observations provide essential measurements of key parameters governing tropical cyclones. They are critical for short-term forecasting. Radiometers onboard the Defense Meteorological Satellite Program satellite series, WindSat and Tropical Rainfall Measuring Mission satellites, scatterometers onboard the ERS, ADEOS, and QuikScat satellites offer unprecedented synoptic observations of surface wind and atmospheric liquid water content, revealing the storm structures with good accuracy. However, satellite estimates do not provide direct measurements of geophysical parameters and can suffer from limitations linked to the sensors... |
| Tipo: Text |
Palavras-chave: Mesearement limitations; Dual frequency altimeter; High resolution measurement; Tropical cyclone. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1033.pdf |
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| 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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| Matsumoto, Haru; Bohnenstiehl, Delwayne R.; Tournadre, Jean; Dziak, Robert P.; Haxel, Joseph H.; Lau, T. -k. A.; Fowler, Matt; Salo, Sigrid A.. |
| In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrated in the southernmost Pacific Ocean. Archived acoustic records show that the high-intensity underwater sounds accompanying this breakup increased ocean noise levels at mid-to-equatorial latitudes over a period of ∼1.5 years. More typically, seasonal variations in ocean noise, which are characterized by austral summer-highs and winter-lows, appear to be modulated by the annual cycle of Antarctic iceberg drift and subsequent disintegration. This seasonal pattern is observed in all three Oceans of the Southern Hemisphere. The life cycle of Antarctic icebergs affects not only marine ecosystem but also the sound environment in far-reaching areas and must be... |
| Tipo: Text |
Palavras-chave: Antarctica; Iceberg; Ocean noise; Seasonality; Trend. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00205/31613/30035.pdf |
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| Tournadre, Jean. |
| Radar meteorologists have estimated, over a number of years, rainfall rate with ground-based radars. Since the 1970s, use of weather radar as an active technique to measure rainfall from space has been proposed, and a number of radar concepts, including modified radar altimeter design, were proposed. However, no attempt has yet been made to determine rain cell characteristics from available altimeter data. This paper presents a method to estimate rainfall rate and rain cell diameter from TOPEX/Poseidon dual frequency radar altimeter waveforms. The rain-affected waveforms are first selected using a criterion based on a departure from a normal Ku-C-band backscatter coefficient relationship and on a threshold of liquid water content estimated by the TOPEX... |
| Tipo: Text |
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| Ano: 1998 |
URL: http://archimer.ifremer.fr/doc/00448/55941/57483.pdf |
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| Krug, M.; Tournadre, Jean. |
| Ocean models show an annual cycle in the Agulhas Current transport which has not yet been confirmed in analyses of in-situ or satellite observations. A cross-stream coordinate approach is used to study the variability of the Agulhas Current from 18 years of along-track altimetry and merged altimetry and close to 7 years of high frequency Sea Surface Temperature (SST) observations. While the position and width of the Agulhas Current's dynamical core do not display an annual cycle, the geostrophic current speed at the current's core exhibits distinct seasonal variations, with a stronger flow observed in austral summer. The annual cycle dominates the frequency spectra of the current's core geostrophic velocities. Citation: Krug, M., and J. Tournadre (2012),... |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00092/20329/17976.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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| Hauser, Danièle; Branger, H; Bouffies Cloche, S; Despiau, S; Drennan, W; Dupuis, H; Durand, P; De Madron, X; Estournel, C; Eymard, L; Flamant, C; Graber, H; Guerin, C; Kahma, K; Lachaud, G; Lefevre, J; Pelon, J; Petterson, H; Piguet, B; Queffeulou, Pierre; Tailliez, D; Tournadre, Jean; Weill, A. |
| The "flux, etat de la mer, et tele'de'tection en conditions de fetch variable'' (FETCH) was aimed at studying the physical processes associated with air-sea exchanges and mesoscale oceanic circulation in a coastal region dominated by frequent strong offshore winds. The experiment took place in March-April 1998 in the northwestern Mediterranean Sea (Gulf of Lion). Observations were collected with the R/V L'Atalante, with an air-sea interaction spar (ASIS) buoy, with waverider buoys, and with research aircraft equipped for in situ and remote sensing measurements. The present paper is an introduction to the following special section, which groups 12 papers (including this one) presenting results on turbulent flux measurements at the ocean surface, on the... |
| Tipo: Text |
Palavras-chave: Gulf of Lion; Coastal oceanography; Marine atmospheric boundary layer; Remote sensing; Surface ocean waves; Air/sea interactions. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-747.pdf |
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| Krug, Marjolaine; Tournadre, Jean; Dufois, F.. |
| Interactions between the Agulhas Current and the ecologically important region of the Agulhas Bank are studied through the analysis of high resolution along-track altimetry, merged mapped altimetry and in situ measurements of current speed and direction undertaken from a moored Accoustic Doppler Current Profiler (ADCP). Comparisons between current observations collected from the ADCP and the satellite altimeters are made to evaluate the validity of the analysis conducted on the altimetry. Both altimetry and in situ observations show that Natal Pulses are a major driver of variability along the eastern margin of the Agulhas Bank. On average, it is estimated that the circulation along the eastern margin of the Agulhas Bank is influenced by Natal Pulses for... |
| Tipo: Text |
Palavras-chave: Agulhas Current; Agulhas Bank; Natal pulse; Satellite oceanography; Altimetry. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00186/29676/28457.pdf |
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| Marc, Benoit; Hervé, Tournadre; Jean-Pierre, Dulphy; Jacques, Cabaret; Sophie, Prache. |
| Two sheep flocks were managed organically (for two years from conversion onwards) under different lambing strategies (1 lambing/year vs. 3 lambings every two years). The second system was tested as there was a producer’s interest in high productivity that is a guarantee of good economic results in conventional. Reproduction, feeding, lamb production, carcass quality, health (particularly internal parasitism), economic return of the flock, grass production, and pasture biodiversity were evaluated. The lambs were bred under low therapeutic input. The economical advantage of increasing lambing frequency was not demonstrated, whereas this strategy complexified management and resulted in higher internal parasitic infection of the lambs, and finally showed a... |
| Tipo: Conference paper, poster, etc. |
Palavras-chave: Sheep and goats; Health and welfare. |
| Ano: 2005 |
URL: http://orgprints.org/7049/1/25048ANdefsent.pdf |
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| Registros recuperados: 40 | |
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