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Nontidal ocean loading: amplitudes and potential effects in GPS height time series / Tonie M. van Dam in Journal of geodesy, vol 86 n° 11 (November 2012)
[article]
Titre : Nontidal ocean loading: amplitudes and potential effects in GPS height time series Type de document : Article/Communication Auteurs : Tonie M. van Dam, Auteur ; Xavier Collilieux , Auteur ; Jan Wuite, Auteur ; Zuheir Altamimi , Auteur ; Jim Ray, Auteur Année de publication : 2012 Article en page(s) : pp 1043 - 1057 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] effet de charge
[Termes IGN] hauteurs de mer
[Termes IGN] masse
[Termes IGN] positionnement par GPS
[Termes IGN] série temporelle
[Termes IGN] surcharge océaniqueRésumé : (Auteur) Ocean bottom pressure (OBP) changes are caused by a redistribution of the ocean’s internal mass that are driven by atmospheric circulation, a change in the mass entering or leaving the ocean, and/or a change in the integrated atmospheric mass over the ocean areas. The only previous global analysis investigating the magnitude of OBP surface displacements used older OBP data sets (van Dam et al. in J Geophys Res 129:507–517, 1997). Since then significant improvements in meteorological forcing models used to predict OBP have been made, augmented by observations from satellite altimetry and expendable bathythermograph profiles. Using more recent OBP estimates from the Estimating the Circulation and Climate of the Ocean (ECCO) project, we reassess the amplitude of the predicted effect of OBP on the height coordinate time series from a global distribution of GPS stations. OBP-predicted loading effects display an RMS scatter in the height of between 0.2 and 3.7 mm, larger than previously reported but still much smaller (by a factor of 2) than the scatter observed due to atmospheric pressure loading. Given the improvement in GPS hardware and data analysis techniques, the OBP signal is similar to the precision of weekly GPS height coordinates. We estimate the effect of OBP on GPS height coordinate time series using the MIT reprocessed solution, mi1. When we compare the predicted OBP height time series with mi1, we find that the scatter is reduced over all stations by 0.1 mm on average with reductions as high as 0.7 mm at some stations. More importantly we are able to reduce the scatter on 65 % of the stations investigated. The annual component of the OBP signal is responsible for 80 % of the reduction in scatter on average. We find that stations located close to semi-enclosed bays or seas are affected by OBP loading to a greater extent than other stations. Numéro de notice : A2012-579 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0564-5 Date de publication en ligne : 06/05/2012 En ligne : https://doi.org/10.1007/s00190-012-0564-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32025
in Journal of geodesy > vol 86 n° 11 (November 2012) . - pp 1043 - 1057[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 266-2012111 RAB Revue Centre de documentation En réserve L003 Disponible The effect of using inconsistent ocean tidal loading models on GPS coordinate solutions / Y. Fu in Journal of geodesy, vol 86 n° 6 (June 2012)
[article]
Titre : The effect of using inconsistent ocean tidal loading models on GPS coordinate solutions Type de document : Article/Communication Auteurs : Y. Fu, Auteur ; J. Freymueller, Auteur ; Tonie M. van Dam, Auteur Année de publication : 2012 Article en page(s) : pp 409 - 421 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] coordonnées GPS
[Termes IGN] géocentre
[Termes IGN] masse de la Terre
[Termes IGN] surcharge océaniqueRésumé : (Auteur) We use up to a 6-year span of GPS data from 85 globally distributed stations to compare solutions using ocean tidal loading (OTL) corrections computed in different reference frames: center of mass of the solid Earth (CE), and center of mass of the Earth system (CM). We compare solution sets that differ only in the frame used for the OTL model computations, for three types of GPS solutions. In global solutions with all parameters including orbits estimated simultaneously, we find coordinate differences of ~0.3 mm between solutions using OTL computed in CM and OTL computed in CE. When orbits or orbits and clocks are fixed, larger biases appear if the user applies an OTL model inconsistent with that used to derive the orbit and clock products. Network solutions (orbits fixed, satellite clocks estimated) show differences smaller than 0.5 mm due to model inconsistency, but PPP solutions show distortions at the ~1.3 mm level. The much larger effect on PPP solutions indicates that satellite clock estimates are sensitive to the OTL model applied. The time series of coordinate differences shows a strong spectral peak at a period of ~14 days when inconsistent OTL models are applied and smaller peaks at ~annual and ~semi-annual periods, for both ambiguity-free and ambiguity-fixed solutions. These spurious coordinate variations disappear in solutions using consistent OTL models. Users of orbit and clock products must ensure that they use OTL coefficients computed in the same reference frame as the OTL coefficients used by the analysis centers that produced the products they use; otherwise, systematic errors will be introduced into position solutions. All modern products should use loading models computed in the CM frame, but legacy products may require loading models computed in the CE frame. Analysts and authors need to document the frame used for all loading computations in product descriptions and papers. Numéro de notice : A2012-243 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0528-1 Date de publication en ligne : 23/11/2011 En ligne : https://doi.org/10.1007/s00190-011-0528-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31689
in Journal of geodesy > vol 86 n° 6 (June 2012) . - pp 409 - 421[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 266-2012061 RAB Revue Centre de documentation En réserve L003 Disponible Hydrological deformation induced by the West African Monsoon : Comparison of GPS, GRACE and loading models / Samuel Nahmani in Journal of geophysical research : Solid Earth, Vol 117 n° B5 (May 2012)
[article]
Titre : Hydrological deformation induced by the West African Monsoon : Comparison of GPS, GRACE and loading models Type de document : Article/Communication Auteurs : Samuel Nahmani , Auteur ; Olivier Bock , Auteur ; Marie-Noëlle Bouin , Auteur ; Alvaro Santamaria Gomez, Auteur ; Jean-Paul Boy, Auteur ; Xavier Collilieux , Auteur ; Laurent Métivier , Auteur ; Isabelle Panet , Auteur ; Pierre Genthon, Auteur ; Caroline de Linage, Auteur ; Guy Wöppelmann , Auteur Année de publication : 2012 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Afrique occidentale
[Termes IGN] coordonnées GPS
[Termes IGN] déformation de la croute terrestre
[Termes IGN] données GRACE
[Termes IGN] données météorologiques
[Termes IGN] effet de charge
[Termes IGN] Gao
[Termes IGN] mousson
[Termes IGN] Niamey (Niger)
[Termes IGN] oscillation
[Termes IGN] Ouagadougou
[Termes IGN] station permanente
[Termes IGN] Tombouctou
[Termes IGN] variation saisonnièreRésumé : (Auteur) Three‐dimensional ground deformation measured with permanent GPS stations in West Africa was used for investigating the hydrological loading deformation associated with Monsoon precipitation. The GPS data were processed within a global network for the 2003–2008 period. Weekly station positions were retrieved with a repeatability (including unmodeled loading effects) of 1–2 mm in the horizontal components and between 2.5 and 6 mm in the vertical component. The annual signal in the vertical component for sites located between 9.6°N and 16.7°N is in the range 10–15 mm. It is consistent at the 3 mm‐level with the annual regional‐scale loading deformations estimated from GRACE satellite products and modeled with a combination of hydrological, atmospheric, and nontidal oceanic models. An additional 6 month transient signal was detected in the vertical component of GPS estimates at most of the West African sites. It takes the form of an oscillation occurring between September and March, and reaching a maximum amplitude of 12–16 mm at Ouagadougou (12.5°N). The analysis of in situ hydro‐geological data revealed a strong coincidence between this transient signal and peak river discharge at three sites located along the Niger River (Timbuktu, Gao, and Niamey). At Ouagadougou, a similar coincidence was found with the seasonal variations of the water table depth. We propose a mechanism to account for this signal that involves a sequence of swelling/shrinking of clays combined with local loading effects associated with flooding of the Niger River. Numéro de notice : A2012-753 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2011JB009102 Date de publication en ligne : 12/05/2012 En ligne : https://doi.org/10.1029/2011JB009102 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91470
in Journal of geophysical research : Solid Earth > Vol 117 n° B5 (May 2012)[article]ITRF2008 contribution to glacial isostatic adjustment and recent ice melting assessment / Laurent Métivier in Geophysical research letters, vol 39 n° 1 (January 2012)
[article]
Titre : ITRF2008 contribution to glacial isostatic adjustment and recent ice melting assessment Type de document : Article/Communication Auteurs : Laurent Métivier , Auteur ; Xavier Collilieux , Auteur ; Zuheir Altamimi , Auteur Année de publication : 2012 Article en page(s) : 6 p. Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] fonte des glaces
[Termes IGN] harmonique sphérique
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] modèle mathématique
[Termes IGN] rebond post-glaciaire
[Termes IGN] vitesseRésumé : (auteur) We investigate what information station vertical velocities of the ITRF2008 provide on global geodetic parameters and by extension on glacial isostatic adjustment (GIA) and recent ice melting (RIM) processes. We infer degree‐2 spherical harmonic coefficients (SHC) of the Earth figure change and theJ2 gravity rate (J˙2), which we compare with five GIA models. We find J˙2 to be (0.0 ± 2.4) × 10−11 yr−1, which is consistent with recent studies that propose a J˙2 change in the 1990s, due to RIM whose contribution to the J˙2 would be today around (3.5–4.0 ± 2.4) × 10−11 yr−1. Such results favor Peltier (2004) VM2 or Paulson et al. (2007) GIA models. The ITRF2008 SHC that are directly impacted by the GIA rotational feedback, confirm with a good precision recent results from GRACE mission that initiated a debate on GIA rotational feedback and about Peltier GIA model quality. We find a coefficient consistent with Paulson's (and other) model and more than 7 times smaller than coefficients in Peltier's models. Two explanations are possible: (1) if the model of Peltier (2004) VM2 were to be correct, then the strong rotational feedback in the model must be counteracted by a strong rotational feedback in the opposite direction generated by current ice loss, (2) if the model of Paulson et al. (2007) were to be correct, therefore GIA and RIM separately induce negligible rotational feedbacks. Both answers are quite extreme and call for more investigation on GIA modeling and rotational feedback. Numéro de notice : A2012-728 Affiliation des auteurs : LAREG (1991-2011) Thématique : POSITIONNEMENT Nature : Article DOI : 10.1029/2011GL049942 Date de publication en ligne : 14/01/2012 En ligne : https://doi.org/10.1029/2011GL049942 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90907
in Geophysical research letters > vol 39 n° 1 (January 2012) . - 6 p.[article]Documents numériques
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ITRF2008 contribution to glacial isostatic adjustment ... - pdf éditeurAdobe Acrobat PDF Modèles de mouvement des plaques tectoniques : Le cas de l’ITRF2008 [diaporama] / Zuheir Altamimi (2012)
Titre : Modèles de mouvement des plaques tectoniques : Le cas de l’ITRF2008 [diaporama] Type de document : Article/Communication Auteurs : Zuheir Altamimi , Auteur ; Laurent Métivier , Auteur ; Xavier Collilieux , Auteur Editeur : Saint-Mandé : Institut national de l'information géographique et forestière - IGN (2012-) Année de publication : 2012 Conférence : Journées Recherche de l’IGN 2012, 21es Journées 08/03/2012 09/03/2012 Saint-Mandé France programme Importance : 23 p. Format : 30 x 21 cm Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] rebond post-glaciaire
[Termes IGN] tectonique des plaquesRésumé : (Auteur) Numéro de notice : C2012-021 Affiliation des auteurs : LASTIG LAREG (2012-mi2018) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComSansActesPubliés-Unpublished DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=64348 Documents numériques
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