Livres anciens
Images
Fonds Jean Bernabé
Fonds René Maran
Esclaves de Guyane
Esclavage en Martinique
Catalogue collectif des périodiques
Audio-Vidéo
Études et recherches
Etudes Caribéennes
Tramil
Or
Esclavage et résistances
5 documents satisfont la requête. Vérifiez les termes recherchés ou relancez la recherche sur le texte intégral
 | Comparison of spaceborne measurements of sea surface salinity and colored detrital matter in the Amazon plume Auteur(s) : Fournier, Severine Chapron, Bertrand Salisbury, J. Vandemark, Douglas Reul, Nicolas Éditeur(s) : Amer Geophysical Union Résumé : Large rivers are key hydrologic components in oceanography, particularly regarding air-sea and land-sea exchanges and biogeochemistry. We enter now in a new era of Sea Surface Salinity (SSS) observing system from Space with the recent launches of the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius/Sac-D missions. With these new sensors, we are now in an excellent position to revisit SSS and ocean color investigations in the tropical northwest Atlantic using multi-year remote sensing time series and concurrent in situ observations. The Amazon is the world's largest river in terms of discharge. In its plume, SSS and upper water column optical properties such as the absorption coefficient of colored detrital matter (acdm) are strongly negatively correlated (<-0.7). Local quasi-linear relationships between SSS and acdm are derived for these plume waters over the period of 2010-2013 using new spaceborne SSS and ocean color measurements. Results allow unprecedented spatial and temporal resolution of this coupling. These relationships are then used to estimate SSS in the Amazon plume based on ocean color satellite data. This new product is validated against SMOS and in situ data and compared with previously developed SSS retrieval models. We demonstrate the potential to estimate tropical Atlantic SSS for the extended period from 1998 to 2010, prior to spaceborne SSS data collection. Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2015-05 , Vol. 120 , N. 5 , P. 3177-3192 Droits : 2015. American Geophysical Union. All Rights Reserved. http://archimer.ifremer.fr/doc/00255/36610/35742.pdf DOI:10.1002/2014JC010109 http://archimer.ifremer.fr/doc/00255/36610/ | Partager Voir aussi Amazon-Orinoco river plume SMOS SSS conservative mixing ocean color salinity satellite oceanography Télécharger |
| | Issues About Retrieving Sea Surface Salinity in Coastal Areas From SMOS Data Auteur(s) : Zine, S Boutin, J Waldteufel, P Vergely, J.l. Pellarin, T Lazure, Pascal Éditeur(s) : IEEE Résumé : This paper aims at studying the quality of the sea surface salinity (SSS) retrieved from soil moisture and ocean salinity (SMOS) data in coastal areas. These areas are characterized by strong and variable SSS gradients [several practical salinity units (psu) on relatively small scales: the extent of river plumes is highly variable, typically at kilometric and daily scales. Monitoring this variability from SMOS measurements is particularly challenging because of their resolution (typically 30-100 km) and because of the contamination by the nearby land. A set of academic tests was conducted with a linear coastline and constant geophysical parameters, and more realistic tests were conducted over the Bay of Biscay. The bias of the retrieved SSS has been analyzed, as well as the root mean square (rms) of the bias, and the retrieved SSS compared to a numerical hydrodynamic model in the semirealistic case. The academic study showed that the Blackman apodization window provides the best compromise in terms of magnitude and fluctuations of the bias of the retrieved SSS. Whatever the type of vegetation cover, a strong negative bias, greater than 1 psu, was found when nearer than 36 km from the coast. Between 44 and 80 km, the type of vegetation cover has an impact of less than a factor 2 on the bias, and no influence further than 80 km from the coast. The semirealistic study conducted in the Bay of Biscay showed a bias over ten days lower than 0.2 psu for distances greater than 47 km, due to an averaging over various geometries (coastline orientation, swath orientation, etc.). The bias showed a weak dependence on the location of the grid point within the swath. Despite the noise on the retrieved SSS, contrasts due to the plume of the Loire River and the Gironde estuary remained detectable on ten-day averaged maps with an rms of 0.57 psu. Finally, imposing thresholds on the major axis of the measurements brought little improvement to the bias, whereas it increased the rms and- could lead to strong swath restriction: a 49-km threshold on the major axis resulted in an effective swath of 800-900 km instead of 1200 km. NOT CONTROLLED OCR Transactions on geoscience an remote sensing IEEE (0196-2892) (IEEE), 2007-07 , Vol. 45 , N. 7 , P. 2061-2072 Droits : 2007 IEEE http://archimer.ifremer.fr/doc/2007/publication-3643.pdf DOI:10.1109/TGRS.2007.894934 http://archimer.ifremer.fr/doc/00000/3643/ | Partager |
| | The SMOS Mission: New Tool for Monitoring Key Elements of the Global Water Cycle Auteur(s) : Kerr, Yann H. Waldteufel, Philippe Wigneron, Jean-pierre Delwart, Steven Cabot, Francois Boutin, Jacqueline Escorihuela, Maria-jose Font, Jordi Éditeur(s) : IEEE Résumé : It is now well understood that data on soil moisture and sea surface salinity (SSS) are required to improve meteorological and climate predictions. These two quantities are not yet available globally or with adequate temporal or spatial sampling. It is recognized that a spaceborne L-band radiometer with a suitable antenna is the most promising way of fulfilling this gap. With these scientific objectives and technical solution at the heart of a proposed mission concept the European Space Agency (ESA) selected the Soil Moisture and Ocean Salinity (SMOS) mission as its second Earth Explorer Opportunity Mission. The development of the SMOS mission was led by ESA in collaboration with the Centre National d'Etudes Spatiales (CNES) in France and the Centro para el Desarrollo Tecnologico Industrial (CDTI) in Spain. SMOS carries a single payload, an L-Band 2-D interferometric radiometer operating in the 1400-1427-MHz protected band [1]. The instrument receives the radiation emitted from Earth's surface, which can then be related to the moisture content in the first few centimeters of soil over land, and to salinity in the surface waters of the oceans. SMOS will achieve an unprecedented maximum spatial resolution of 50 km at L-band over land (43 km on average over the field of view), providing multiangular dual polarized (or fully polarized) brightness temperatures over the globe. SMOS has a revisit time of less than 3 days so as to retrieve soil moisture and ocean salinity data, meeting the mission's science objectives. The caveat in relation to its sampling requirements is that SMOS will have a somewhat reduced sensitivity when compared to conventional radiometers. The SMOS satellite was launched successfully on November 2, 2009. Proceedings of the IEEE (0018-9219) (IEEE), 2010-05 , Vol. 98 , N. 5 , P. 666-687 Droits : 2010 IEEE – All Rights Reserved http://archimer.ifremer.fr/doc/00004/11483/8065.pdf DOI:10.1109/JPROC.2010.2043032 http://archimer.ifremer.fr/doc/00004/11483/ | Partager |
| | First Assessment of SMOS Data Over Open Ocean: Part II-Sea Surface Salinity Auteur(s) : Boutin, Jacqueline Martin, Nicolas Yin, Xiaobin Font, Jordi Reul, Nicolas Spurgeon, Paul Éditeur(s) : Ieee-inst Electrical Electronics Engineers Inc Résumé : 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 the foam effect is less than previously modeled. Given the large noise on individual SMOS measurements, a precision suitable for oceanographic studies can only be achieved after averaging SMOS SSS. Over selected regions and after mean bias removal, the precision on SSS retrieved from ascending orbits and averaged over 100 km $times$ 100 km and 10 days is between 0.3 and 0.5 pss far from land and sea ice borders. These results have been obtained with forward models not fitted to satellite L-band measurements, and image reconstruction and instrument calibration are expected to improve. Hence, we anticipate that deducing, from SMOS measurements, SSS maps at 200 km $times$ 200 km, 10 days resolution with an accuracy of 0.2 pss at a global scale is not out of reach. Ieee Transactions On Geoscience And Remote Sensing (0196-2892) (Ieee-inst Electrical Electronics Engineers Inc), 2012-05 , Vol. 50 , N. 5 , P. 1662-1675 Droits : 2012 IEEE http://archimer.ifremer.fr/doc/00074/18557/16108.pdf DOI:10.1109/TGRS.2012.2184546 http://archimer.ifremer.fr/doc/00074/18557/ | Partager |
| | Demonstration of ocean surface salinity microwave measurements from space using AMSR-E data over the Amazon plume Auteur(s) : Reul, Nicolas Saux Picart, Stephane Chapron, Bertrand Vandemark, D. Tournadre, Jean Salisbury, J. Éditeur(s) : American Geophysical Union Résumé : 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 dedicated mission objectives. Citation: Reul, N., S. Saux-Picart, B. Chapron, D. Vandemark, J. Tournadre, and J. Salisbury (2009), Demonstration of ocean surface salinity microwave measurements from space using AMSR-E data over the Amazon plume, Geophys. Res. Lett., 36, L13607, doi:10.1029/2009GL038860. Geophysical Research Letters ( GRL ) (0094-8276) (American Geophysical Union), 2009-07 , Vol. 36 , P. 1-5 Droits : 2009. American Geophysical Union. All Rights Reserved http://archimer.ifremer.fr/doc/2009/publication-6620.pdf DOI:10.1029/2009GL038860 http://archimer.ifremer.fr/doc/00000/6620/ | Partager |