Philippe JEAN-PIERRE

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Jean-Philippe BoulangerChristophe Menkes
• Organismes : Laboratoire d'océanographie dynamique et de climatologie Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
• Publié dans Climate Dynamics le 30/10/2020

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Résumé : The TOPEX/POSEIDON sea level data have been shown to observe the sea surface height variability accurately over the globe and, more particularly, in the tropical Pacific, core region of the El Niño/Southern Oscillation. Various studies have already provided descriptions of long equatorial wave propagation as well as estimates of their reflection at both the eastern and western boundaries using TOPEX/POSEIDON data over short time periods. In this present work, we are first interested in computing long equatorial wave amplitudes over a much longer period (October 1992-May 1998) focusing on the Kelvin and first three largest Rossby waves. Secondly, we are examining qualitatively potential theories of ENSO in the light of observations of the strong 1997-1998 El Niño event. At the eastern boundary, Kelvin waves are observed to reflect into first (third) mode Rossby waves with a reflection efficiency of 75% (65%) of that of an infinite meridional wall. In the western Pacific Ocean, the reflection of the first Rossby wave does explain more than 90% of the Kelvin wave variance. The second Rossby wave is found not to be correlated to the Kelvin wave amplitude, and the third Rossby wave is highly correlated to the Kelvin signal although its contribution is weak. The investigation during the 1997-1998 event of two theories potentially important for ENSO (the delayed action oscillator mechanism and the recent theory of Picaut et al., 1997) led us to the following conclusions. The westerly wind anomalies observed in the western Pacific in December 1996 and March 1997 forced downwelling Kelvin waves which advected the eastern edge of the warm pool eastward and deepened the thermocline in the east Pacific. Both zonal advection and vertical processes are suggested to act constructively during the onset of positive anomalies in the central and eastern Pacific. From May to September 1997, downwelling Kelvin wave wind-forced in the central Pacific and reflected downwelling Rossby waves (reinforced by local easterly wind anomalies) acted against each other, and the 28°C isotherm was found to move slightly westward. In October 1997, strong westerly wind anomalies forced a strong downwelling Kelvin wave potentially responsible for the strong warming in the east Pacific. The 28°C isotherm reached the eastern boundary. At that time, the equatorial sea surface temperatures are zonally homogeneous. The strong downwelling Rossby waves reflected at the boundary could not act to terminate the warm event through zonal advection as suggested by Picaut et al. However the reflected upwelling Kelvin waves coming from the western boundary weakened the downwelling Kelvin signal in the central and east Pacific leading to a decrease of the sea surface temperature anomalies. Following this decrease, westerly wind anomalies in the central Pacific weakened, and upwelling Kelvin waves reinforced by easterly wind anomalies in the western Pacific propagated toward the eastern Pacific. As a conclusion, both theories must be considered simultaneously to understand the variability observed during the 1997-1998 El Niño event. However observations strongly suggest the delayed action oscillator mechanism to be the major process at work during the weakening of the warm 1997-1998 ENSO.

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/1999
• Auteurs : J.L. ZaraderBruno GasPhilippe DrobinskiP. Dabas
• Organismes : Institut des Systèmes Intelligents et Robotique Sorbonne Université Institut des Systèmes Intelligents et Robotique Laboratoire de Météorologie Dynamique (UMR 8539)

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Philippe BiaginiPierre GallianHoussam AttouiJean-François CantaloubePhilippe de MiccoXavier de Lamballerie
• Organismes : Virologie UMR1161
• Publié dans Journal of General Virology le 01/11/2020

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• Type de publi. : Chapître d'ouvrage
• Date de publi. : 01/01/1999
• Auteurs : Philippe Sénac
• Organismes : France, Amériques, Espagne, Sociétés, Pouvoirs, Acteurs

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• Type de publi. : Chapître d'ouvrage
• Date de publi. : 01/01/1999
• Auteurs : Philippe Jean-PierreJean-Yves Rochoux
• Organismes : Centre d'Économie et de Management de l'Océan Indien Université de La Réunion Centre d'Économie et de Management de l'Océan Indien

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/1999
• Auteurs : Pierre BouletJean-Luc DekeyserAlain DemeureFlorent DevinPhilippe Marquet
• Organismes : Laboratoire d'Informatique Fondamentale de Lille Contributions of the Data parallelism to real time Laboratoire d'Informatique Fondamentale de Lille Contributions of the Data parallelism to real time Laboratoire d'Informatique Fondamentale de Lille Laboratoire d'Informatique Fondamentale de Lille Contributions of the Data parallelism to real time

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Résumé : The Gaspard (Graphical Array Specification for PARallel and Distributed computing) project is a visual specification environment for data-parallelism. We describe here the specification model used in Gaspard. This model inherits from the Array-OL one. We then define an SQL inspired approach to intensive data treatment that proposes a language to describe irregular components.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Philippe BallonBenoît GuibertJean-Pierre HamardNadine GuillonY. Boscardin
• Organismes : Écosystèmes forestiers et paysages Office National des Forêts Écosystèmes forestiers et paysages Centre d'Études Biologiques de Chizé Écosystèmes forestiers et paysages
• Publié dans Revue forestière française le 29/10/2020

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Résumé : Les observations contrôlées de chevreuils en captivité ont permis de préciser la sensibilité à l'abroutissement de certaines essences forestières de reboisement (chênes, hêtre, feuillus dits "précieux", sapin pectiné, pin maritime). Pour cela, nos expérimentations ont consisté à présenter simultanément, à plusieurs groupes d'animaux, pendant un temps limité, une même essence de caractéristiques différentes ou plusieurs essences différentes. Nos résultats mettent en évidence expérimentalement de fortes variations de niveaux de consommation des essences de reboisement en fonction de leur nature (plant, semis naturel, rejet) et de certaines techniques d'élevage des plants en pépinière. Ainsi, a été confirmé expérimentalement ce que des gestionnaires forestiers connaissaient de façon empirique, comme une plus grande sensibilité des plants de chêne sessile par rapport aux semis naturels. Par contre, nos résultats démontrent l'absence de différences d'appétence entre des plants de chêne "forcés" en pépinière et d'autres élevés "normalement". Enfin dans certains cas, des éléments nouveaux ont été mis en évidence comme par exemple la plus grande sensibilité des sapins conditionnés en motte par rapport à ceux élevés en racine nue. Ces observations permettent de préciser les risques d'apparition de dégâts d'abroutissement par le chevreuil et de guider le gestionnaire forestier dans ses choix sylvicoles.

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Fichiers liés : 20_34.pdf

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Philippe GaussierCédric JoulainJean-Paul BanquetArnaud RevelSacha Lepretre
• Organismes : Equipes Traitement de l'Information et Systèmes Equipes Traitement de l'Information et Systèmes Plasticité cérébrale et adaptations des fonctions visuelles et motrices Equipes Traitement de l'Information et Systèmes Equipes Traitement de l'Information et Systèmes
• Publié dans Industrial Robot le 23/10/2009

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Résumé : Psychology and neurobiology nowadays provide a large amount of precise information on visual system function. This information can be used in the design of autonomous systems capable of learning and recognising objects and places important for survival in complex unknown (real or virtual) environments. Our work is based on the principles that perception is fundamentally a dynamic process in constant interaction with movement; and that learning can be made simpler if the systems are not required to learn the invariants of their environment (e.g. preservation of neighbour topological relations, or connectivity of the space). The techniques that contribute to devising these adaptive systems in continuous interaction with their environment could significantly influence our approach to programming and the man-machine interface.

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/1999
• Auteurs : Philippe WaldteufelEric AnterrieuJean-Marc GoutouleYann H. Kerr
• Organismes : Service d'aéronomie Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique Centre d'études spatiales de la biosphère

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Résumé : Recently developed interferometric techniques allow to design realistic space missions using L-Band radiometry, devoted to remote sensing of soil moisture (over land) and surface salinity (over the ocean) at the Earth surface. The SMOS mission, submitted to the European Space Agency, uses the 2-D interferometric MIRAS concept, developed since 1993 by ESA. The MIRAS antenna is a Y shaped structure, each arm of which consists of aligned, adjacent elementary antennas. Visibility functions are retrieved from the correlation products constructed from the signals collected by elementary antennas, then transformed into brightness temperature maps. The field of view (FOV) is limited both by the solid angle where visibility functions can be reconstructed and by aliased Earth images. The alias free FOV roughly consists of two regions. In the "inner" swath, a large range of look angles is explored instantaneously ; the same region on Earth can thus be seen for a variety of incidence angles. This may strongly improve the accuracy and power of retrieving procedures. In the "outer" swath, the range of angles decreases: the 2-D radiometer then becomes comparable to a conical scanning radiometer. This duality may help to optimise mission scenarios in terms of revisit time and measurement performances. Over the ocean, an averaging procedure is necessary, in order to estimate surface salinity with adequate accuracy. What then matters is the total number and accuracy of instantaneous independant views. It is shown that 2-D interferometric designs do not suffer major degradations when compared to real antennas.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Gaëtan MessinJean-Philippe KarrHichem EleuchJean-Michel CourtyElisabeth Giacobino
• Organismes : Laboratoire Kastler Brossel Laboratoire Kastler Brossel Laboratoire Kastler Brossel Laboratoire Kastler Brossel Laboratoire Kastler Brossel
• Publié dans Journal of Physics: Condensed Matter le 26/10/2020

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Résumé : A theoretical investigation of the quantum noise in the light reflected by a microcavity containing a semiconductor quantum well is presented. Squeezing is predicted when scattering processes have a low efficiency. Exciton-phonon scattering is shown to destroy the non-classical effects and to yield excess noise in the output field.

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