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Identification and modelling of sea level change contributors on GRACE satellite gravity data and their applications to climate monitoring / Bert Wouters (2010)
Titre : Identification and modelling of sea level change contributors on GRACE satellite gravity data and their applications to climate monitoring Type de document : Rapport Auteurs : Bert Wouters, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2010 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 73 Importance : 182 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-90-6132-316-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] changement climatique
[Termes IGN] GRACE
[Termes IGN] Groenland
[Termes IGN] niveau moyen des mers
[Termes IGN] surveillance météorologiqueIndex. décimale : 30.83 Applications océanographiques de géodésie spatiale Résumé : (Auteur) Recently, the Intergovernmental Panel on Climate Change named sea level rise as one of the major challenges of the 21st century. Given the high population density of coastal regions, a small rise of the sea level will have a substantial impact on human society. However, the Earth's climate system is a complex matter arid model predictions of the sea level changes likely to be expected in the coming century currently show a wide spread. Clearly, a thorough understanding of present-day climate variability is imperative narrow this uncertainty band, which on its turn depends on the availability of accurate and detailed observations of our climate.
A valuable contribution to the expanding array of satellites dedicated to observations of the Earth System, are the Gravity Recovery and Climate Experiment (GRACE) satellites, launched in March 2002. This mission is dedicated to observing changes of the Earth's gravity field at (sub-)monthly intervals. At time-scales of a few years, these changes are mostly related to the redistribution of water on the Earth's surface. For example, a thinning of the Greenland ice sheet will manifest itself as a local negative anomaly in the gravity field, whereas the water that is added to the ocean will show up as a predominantly positive anomaly. The main objective of this dissertation is to study how the GRACE observations can be used to improve our knowledge of changes in the Earth's climate systems, and how the data should be processed in order to optimize quality and spatial resolution.
The GRACE data provided by the science teams consist of spherical harmonic coefficients. They show particular correlations between coefficients of identical order and even and odd degree, respectively, due to the mission's architecture and deficiencies in the background models used throughout the processing of the satellite measurements. These noise artifacts show up as striping patterns along the north-south direction in the monthly maps of surface mass changes, hampering the interpretation of the observations. In this dissertation, it is shown that empirical orthogonal function (EOF) analysis is an effective method to reduce the noise in the GRACE data. This statistical tool separates a data set into a number of characteristic (eigen) modes of variance, in combination with an index describing the amplitude of the mode in time, i.e. the principal components. The EOF analysis can be applied to the maps of surface mass changes, in which case the first few modes are related to the annual and long-term trend components. The fourth mode appears to be related to the El Nino/Southern Oscillation. The noise signals arc absorbed by the higher modes, which makes the leading modes largely stripe-free up to a resolution of approximately 400 kilometers.
A further reduction of the noise can be obtained by applying the EOF de-composition directly to the spherical harmonic coefficients, after grouping them following order. The principal components arc compared to a random process and, if the two arc statistically sufficiently alike, not used in the further data processing. A series of tests shows that this approach reduces the noise by 60-80 %, compared the non-filtered case. An important feature of this filter is that it does not alter the shape of the signal and causes less reduction its power, compared to other commonly used filter methods based on the approach of Swenson and Walir (2006).
Using the filtered data, changes in the mass content of the ocean have been studied. The GRACE satellites are capable of capturing seasonal changes in the ocean mass content accurately on a global scale. In combination with sea surface height observations made by satellite altimeter, the steric sea level component (related to changes in the heat and salinity content of the ocean) can be separated as well. A comparison with reference data sets shows that locally a coherent signal can be obtained at a (Gaussian) resolution of approximately 500 km over the oceans. These steric changes dominate the sea level in most of the oceans, but strong ocean bottom pressure fluctuations are observed in several areas, e.g., the Gulf of Carpentaria and the Gulf of Thailand. Estimates of long-term changes in the ocean mass and heat content arc a more challenging problem, and require a longer observation period and a better modeling of mass redistribution in the solid earth and the position of the center of mass of the Earth, two components to which the GRACE observations arc particularly sensitive.
It is found that the global spherical harmonic coefficients contain more information than previously acknowledged. This is demonstrated by using the GRACE data to obtain a picture of the mass balance of the Greenland ice sheet at a regional scale. From the research in this dissertations, it shows that Greenland lost 179 Gigaton each year on average between 2003 and 2008, causing a global mean rise of sea level by 0.5 mm/yr. Comparing the trend in the first few to that in the last few years shows a speed-up of the thinning, which corroborates the picture of an increasingly negative mass balance of the ice sheet since the mid 1990's as indicated by, for example, regional climate models and radar altimetry observations. The majority of the losses occur in the coastal regions in the southeastern sector. The northwestern coastal zones were approximately in balance up to the summer of 2005, but show strong negative trends since. Large year-to-year differences in the mass balance of the ice sheet are observed, with a record loss in the warm summer of 2007. A strong correlation between the GRACE observations in summer and satellite measurements of surface melt area extent is demonstrated. Also, good agreement is found with regional climate modeling data, highlighting the potential of the GRACE observations to validate and improve the numerical models.
A mass redistribution on land will cause a change in the shape of the global geoid. Sea level, when not acted upon by any other forcings, will adjust to this equipotential surface. Therefore, when water is exchanged between ocean and continents (and changes due to ocean dynamics are disregarded), sea level will not rise or fall uniformly, which is known as the so-called self-gravitation effect. Due to their global coverage, the GRACE observations of continental mass distribution are an excellent input to model this phenomenon. Strongest deviations from a uniform distribution are found off the coast of Alaska and in the Bay of Bengal, where differences of more than 100% are found on seasonal time-scales. In these regions, inclusion of the self-gravitation effect into numerical ocean model would result in a better agreement between modeled and observational data.
From the work presented in this dissertation, it shows that the GRACE satellites are an invaluable tool for the monitoring of our climate system. Statistically filtering of the data reveals a wealth of information. In combination with altimetry observations, the GRACE data allows the separation of mass and steric components in sea level on seasonal time scales. Given a longer observational period and an improved understanding of the processes in the solid earth, expected to come available soon thanks to ESA's GOCE missions, long-term trends in these components will be identifiable. Furthermore, the GRACE mission allows us to put a constraint on the contribution of the Greenland ice sheet to present-day sea level rise. The technique to recover these changes can easily be expanded to other regions, such as the Antarctic or the Alaskan glacier fields. The synergy between GRACE data, future missions such as Cryosat-2, which will map height variations of the cryosphere with an unprecedented accuracy, and regional climate models, uncovering the physical processes behind the observed changes, promises a leap forward in our understanding of the mass balance of the ice sheets. Finally, com-paring the modeled deviations from uniform sea level changes with in-situ data such as from tide-gauges, may lead to a direct validation of the aforementioned self-gravitation theory with present-day data.Numéro de notice : 10335 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport de recherche DOI : sans En ligne : https://www.ncgeo.nl/downloads/73Wouters.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62396 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 10335-01 30.83 Livre Centre de documentation Géodésie Disponible Mise en place d’une chaîne de calcul ultra rapide des orbites et des corrections d’horloges des satellites GLONASS / Oussama Ben Abdelaziz (2010)
Titre : Mise en place d’une chaîne de calcul ultra rapide des orbites et des corrections d’horloges des satellites GLONASS Type de document : Mémoire Auteurs : Oussama Ben Abdelaziz, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2010 Importance : 72 p. Format : 21 x 30 cm Note générale : Bibliographie
Rapport de Projet de Fin d’Etudes, Cycle des Ingénieurs diplômés de l’ENSG 3ème année (IT3), [master PPMD]Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] calcul d'erreur
[Termes IGN] erreur systématique
[Termes IGN] Global Orbitography Navigation Satellite System
[Termes IGN] horloge
[Termes IGN] orbite
[Termes IGN] satellite GLONASSIndex. décimale : MPPMD Mémoires du mastère spécialisé Photogrammétrie, Positionnement et Mesures de Déformation Résumé : (Auteur) Depuis la fin de l'année 2008, l'IGN fournit une solution ultra rapide des orbites et des corrections d'horloges des satellites GPS. Le but de mon projet de fin d'études fut d'enrichir ce produit en y ajoutant les orbites et les corrections d'horloges des satellites GLONASS. Dans ce document nous décrivons en détail les différentes modifications apportées à la chaîne de calcul et justifions les choix techniques effectués en fournissant une présentation théorique rigoureuse des problématiques liées à la réalisation d'un calcul combiné GPS/GLONASS, notamment l'existence de différents biais : biais inter-systèmes et biais inter-fréquences dont la compréhension fut indispensable au bon déroulement du projet. Note de contenu : 1- Introduction
2- Etudes Préliminaires
1) Présentation du système GLONASS
a) Un peu d'histoire
b) Le segment spatial
c) Le segment terrestre
d) Le segment utilisateur
e) Les systèmes de référence
f) Le signal GLONASS
g) Les équations d'observation
2) Présentation du produit SGU
a) Déroulement du calcul opérationnel
b) Qualité des orbites et des corrections d'horloges SGU
c) Effet de l'augmentation du pas d'échantillonnage sur la qualité des orbites et des corrections d'horloges
3) Etude de l'existant
a) Produits disponibles
b) Problèmes rencontrés lors du traitement des données GLONASS avec le Bernese
c) GLONASS au SGN
3- Collecte et prétraitement des données
1) Choix des stations
2) Téléchargement des données
3) Prétraitement des données
4- Calcul des orbites
1) Déroulement opérationnel du calcul
2) La fixation des ambigüités
5- Calcul des horloges
1) Un point sur la théorie
2) Problèmes liés aux biais et déroulement opérationnel du calcul
6- ConclusionNuméro de notice : 10916 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Mémoire masters divers Organisme de stage : IGN Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=49419 Réservation
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10916_mem_chaine_calcul_orbites_glonass_ben-abdelaziz.pdfAdobe Acrobat PDF IGN Espace fêtait ses vingt ans / Anonyme in Géomatique expert, n° 72 (01/12/2009)
[article]
Titre : IGN Espace fêtait ses vingt ans Type de document : Article/Communication Auteurs : Anonyme, Auteur Année de publication : 2009 Article en page(s) : pp 11 - 13 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] correction géométrique
[Termes IGN] Guyane française
[Termes IGN] HRS (capteur)
[Termes IGN] IGN ESPACE
[Termes IGN] image à très haute résolution
[Termes IGN] image spatiale
[Termes IGN] Institut géographique national (France)
[Termes IGN] modèle numérique de terrain
[Termes IGN] Référence-3D
[Termes IGN] spatiocarte
[Termes IGN] SPOT Image
[Termes IGN] SPOT5
[Termes IGN] temps réel
[Termes IGN] traitement d'imageRésumé : (Auteur) Créée en 1989 pour se rapprocher des activités spatiales alors jugées stratégiques, IGN Espace, une filiale de l'institut, fête ses vingt ans. C'était l'occasion de revenir sur un parcours riche, de faire le point sur les activités présentes et futures. Copyright CiMax Numéro de notice : A2009-534 Affiliation des auteurs : IGN (1940-2011) Thématique : IMAGERIE Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30163
in Géomatique expert > n° 72 (01/12/2009) . - pp 11 - 13[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 265-09071 RAB Revue Centre de documentation En réserve L003 Disponible IFN-001-P000736 PER Revue Nogent-sur-Vernisson 1er étage - Carto Exclu du prêt Geocenter variations derived from GPS tracking of the GRACE satellites / Z. Kang in Journal of geodesy, vol 83 n° 10 (October 2009)
[article]
Titre : Geocenter variations derived from GPS tracking of the GRACE satellites Type de document : Article/Communication Auteurs : Z. Kang, Auteur ; B. Tapley, Auteur ; J. Chen, Auteur ; John Ries, Auteur ; S. Bettadpur, Auteur Année de publication : 2009 Article en page(s) : pp 895 - 901 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] géocentre
[Termes IGN] GRACE
[Termes IGN] orbite basse
[Termes IGN] orbitographie par GNSS
[Termes IGN] poursuite de satelliteRésumé : (Auteur) Two 4.5-year sets of daily geocenter variations have been derived from GPS-LEO (Low-Earth Orbiter) tracking of the GRACE (Gravity Recovery And Climate Experiment) satellites. The twin GRACE satellites, launched in March 2002, are each equipped with a BlackJack global positioning system (GPS) receiver for precise orbit determination and gravity recovery. Since launch, there have been significant improvements in the background force models used for satellite orbit determination, most notably the model for the geopotential, which has resulted in significant improvements to the orbit determination accuracy. The purpose of this paper is to investigate the potential for determining seasonal (annual and semiannual) geocenter variations using GPS-LEO tracking data from the GRACE twin satellites. Internal comparison between the GRACE-A and GRACE-B derived geocenter variations shows good agreement. In addition, the annual and semiannual variations of geocenter motions determined from this study have been compared with other space geodetic solutions and predictions from geophysical models. The comparisons show good agreement except for the phase of the z-translation component. Copyright Springer Numéro de notice : A2009-428 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-009-0307-4 En ligne : https://doi.org/10.1007/s00190-009-0307-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30059
in Journal of geodesy > vol 83 n° 10 (October 2009) . - pp 895 - 901[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-09091 SL Revue Centre de documentation Revues en salle Disponible Architecture for a future C-band/L-band GNSS mission : Part 2 signal considerations and related user terminal aspects / José Avila-Rodriguez in Inside GNSS, vol 4 n° 4 (July - August 2009)
[article]
Titre : Architecture for a future C-band/L-band GNSS mission : Part 2 signal considerations and related user terminal aspects Type de document : Article/Communication Auteurs : José Avila-Rodriguez, Auteur ; J.H. Won, Auteur ; S. Wallner, Auteur ; et al., Auteur Année de publication : 2009 Article en page(s) : 21 p. ; pp 52 - 72 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Missions spatiales
[Termes IGN] bande C
[Termes IGN] bande L
[Termes IGN] charge utile
[Termes IGN] composant électronique
[Termes IGN] interférence
[Termes IGN] mission spatiale
[Termes IGN] signal GNSSRésumé : (Auteur) Almost all GNSS navigation signals operate in the crowded L-band portion of the radio frequency spectrum. In the past, C-band spectrum has been considered — and rejected — for GNSS services due to a couple of substantial obstacles, despite some distinct technical advantages. However, continued proliferation of signals in L-band and advances in electronics and spacecraft technologies have prompted a new look at C-band for future GNSS services. This article is the second of a two-part series describing the results of a new European Space Agency–sponsored study on the subject. Copyright Gibbons Media & Research LLC Numéro de notice : A2009-662 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33563
in Inside GNSS > vol 4 n° 4 (July - August 2009) . - 21 p. ; pp 52 - 72[article]Voir aussiRéservation
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Code-barres Cote Support Localisation Section Disponibilité 159-09041 SL Revue Centre de documentation Revues en salle Disponible Documents numériques
en open access
rchitecture for a future C-band/L-band GNSS ... - pdf éditeurAdobe Acrobat PDF Making sense of inter-signal corrections: accounting for GPS satellite calibration parameters in legacy and modernized ionosphere correction algorithms / Avram Tetewsky in Inside GNSS, vol 4 n° 4 (July - August 2009)PermalinkWhere is GIOVE-A exactly? Using microwaves and laser ranging for precise orbit determination / Erik Schönemann in GPS world, vol 20 n° 7 (July 2009)PermalinkSPOT image tourné vers l'avenir / Françoise de Blomac in SIG la lettre, n° 108 (juin 2009)PermalinkTerraSAR-X and TanDEM-X: Revolution in spaceborne radar / F. Hensler in Bulletin des sciences géographiques, n° 23 (juin 2009)PermalinkArchitecture for a future C-band/L-band GNSS mission: Part 1 C-band services, space- and ground segment, overall performance / A. Schmitz-Peiffer in Inside GNSS, vol 4 n° 3 (May - June 2009)PermalinkDevelopment of data infrastructure to support scientific analysis for the International GNSS Service / Carey E. Noll in Journal of geodesy, vol 83 n° 3-4 (March - April 2009)PermalinkExploring the water cycle of the 'blue planet': the Soil Moisture and Ocean Salinity (SMOS) mission / M. Drinkwater in ESA bulletin, n° 137 (February 2009)PermalinkGetting down to business: SMOS operations and products / S. Mecklenburg in ESA bulletin, n° 137 (February 2009)PermalinkPermalinkApport des mesures directionnelles et polarisées aux corrections atmosphériques au-dessus des océans ouverts. Application à la mission PARASOL / Tristan Harmel (2009)PermalinkObjectifs terre / J.M. Besnier (2009)PermalinkOptima multi-step collocation: application to the space-wise approach for GOCE data analysis / M. Reguzzoni in Journal of geodesy, vol 83 n° 1 (January 2009)PermalinkA study reference frame consistency in recent Earth gravitational models / Christopher Kotsakis in Journal of geodesy, vol 83 n° 1 (January 2009)PermalinkTerrasar-X1M spaceborne radar / M. Weber in GIM international, vol 23 n° 1 (January 2009)PermalinkVariations in the accuracy of gravity recovery due to ground track variability: GRACE, CHAMP, and GOCE / J. Klokocnik in Journal of geodesy, vol 82 n° 12 (December 2008)Permalinkvol 46 n° 11 Tome 1 - November 2008 - Special section on meteorology, climate, ionosphere, geodesy and reflections from the ocean surfaces: studies by radio occultation methods (Bulletin de IEEE Transactions on geoscience and remote sensing) / Geoscience and remote sensing societyPermalinkMultisensor satellite monitoring of seawater state and oil pollution in the northeastern coastal zone of the Black Sea / S. Shcherbak in International Journal of Remote Sensing IJRS, vol 29 n° 21 (October 2008)Permalinkvol 29 n° 21 - October 2008 - Satellite observations of the atmosphere, oceans and their interface in relation to climate, natural hazards and management of coastal zone (Bulletin de International Journal of Remote Sensing IJRS) / G. LevyPermalinkFuture time : opportunities for using optical clocks in GNSS systems / A. Moudrak in Inside GNSS, vol 3 n° 6 (September 2008)PermalinkPotential accuracy of image orientation of small satellites: a case study of CHRIS/Proba data / Ahmed Shaker in Photogrammetric record, vol 23 n° 123 (September - November 2008)Permalink