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scientifique

Field optical clocks and sensitivity to mass anomalies for geoscience applications / Guillaume Lion (2023)  

Public Titre : Field optical clocks and sensitivity to mass anomalies for geoscience applications Type de document : Article/Communication Auteurs : Guillaume Lion , Auteur ; Gwendoline Pajot-Métivier , Auteur ; Kristel Chanard , Auteur ; Michel Diament , Auteur Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2023 Projets : ROYMAGE / Letargat, Rodolphe Conférence : EGU 2023, General Assembly 23/04/2023 28/04/2023 Vienne Autriche OA Abstracts only Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse de sensibilité [Termes IGN] anomalie de pesanteur [Termes IGN] chronométrie [Termes IGN] horloge optique Index. décimale : 30.60 Géodésie spatiale Résumé : (auteur) 350 years ago, the pendulum clock for astronomical observations was diverted to become an instrument for measuring gravity. The measurement of the parallax of Mars by Richer and Cassini from Cayenne and Paris showed that the period of a periodic oscillator depends on the gravity field. A link was thus established between the improvement of time measurement and the knowledge of the phenomena that govern it. Since then, the performance and nature of clocks have evolved considerably. Today, atomic clocks are used in various fields that are essential to modern society, such as the realisation of international atomic time (TAI), satellite navigation (GNSS), geodesy, the traceability of trading events, etc. In the framework of the french ANR ROYMAGE, we are interested in the contribution of a transportable optical field clock for geoscience applications by using the principle of chronometric geodesy. The idea is based on the gravitational redshift, a relativistic effect that predicts that the beat of a clock depends on the speed at which it is moving and the strength of the surrounding gravitational potential. In practice, this means that if we compare the beat of two clocks, then it is possible to directly measure a difference in gravitational potential (or a change in height) between these two clocks. This type of measurement is original because classical geodetic techniques only allow to determine the potential indirectly from gravimetric and classical levelling data. In this work, we model the gravitational signature (potential, acceleration and tensor) of a mass anomaly as a function of its geometry, depth, size and density contrast. These synthetic simulations allow us to identify which types of structures can be detected by clock comparison measurements with a relative frequency uncertainty fixed at 10-17-18-19 (i.e. a vertical sensitivity of less than 10 cm - 1 cm - 1 mm respectively). We are also interested in the spatial resolution required for a clock measurement to detect two mass anomalies depending on its orientation. Finally, we show that this new chronometric observable combined with gravimetry and gradiometry data could allow a better separation of the sources by adding an additional constraint thanks to the medium and long wavelength gravitational information it provides. Numéro de notice : C2023-003 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Autre URL associée : vers HAL Thématique : POSITIONNEMENT Nature : Poster nature-HAL : Poster-avec-CL DOI : 10.5194/egusphere-egu23-3646 En ligne : https://doi.org/10.5194/egusphere-egu23-3646 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103216

A new method for the attribution of breakpoints in segmentation of IWV difference time series / Khanh Ninh Nguyen (2022)  

Public Titre : A new method for the attribution of breakpoints in segmentation of IWV difference time series Type de document : Article/Communication Auteurs : Khanh Ninh Nguyen, Auteur ; Olivier Bock , Auteur ; Emilie Lebarbier, Auteur Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2022 Conférence : EGU 2022, General Assembly 23/05/2022 27/05/2022 Vienne Autriche OA Abstracts only Importance : 1 p. Format : 21 x 30 cm Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] données GNSS [Termes IGN] points de rupture [Termes IGN] segmentation [Termes IGN] série temporelle [Termes IGN] teneur intégrée en vapeur d'eau Résumé : (auteur) In recent years, the detection and correction of the non-natural irregularities in the long climatic records, so-called homogenization, has been studied. This work is motivated by the problem of identification of origins of the breakpoints in the segmentation of difference series (difference between a candidate series and a reference series). Several segmentation methods have been developed for the difference series, but many of them assume that the reference series is homogenous. However, the homogeneity of the reference series, in reality, is uncertain and unproven. In our study, we applied the segmentation method GNSSseg (Quarello et al., 2020) on the difference between the Integrated water vapour estimates of the CODE REPRO2015 GNSS data set and the ERA5 reanalysis. About 36.5% of change points can be validated from the GPS metadata, and the origins of the remaining 64.5% are questionable (Nguyen et al., 2021). The ambiguity can be leveraged when there is at least one nearby GPS station with respect to which the candidate series can be compared. The proposed method uses weighted t-tests combining the candidate GPS and ERA series and their homologues (denoted GPS' and ERA') from each nearby station. If sufficient consistency emerges from the six tests for all the nearby stations, a decision can be made whether the breakpoint detected in the candidate GPS-ERA series is due to GPS or, alternatively, to ERA. For each quadruplet (GPS, ERA, GPS', ERA'), six t-tests are performed, and the outcomes are combined. In a set of 81 globally distributed GNSS time series spanning more than 25 years, 56 series have at least one nearby station, where 171 breakpoints are detected in segmentation, in which 136 breakpoints are attributed to the GPS. Among those, 94 breakpoints have consistent results between all the nearby stations. GPS-related breakpoints are used for the correction of the mean shift in the difference series. The impact of the breakpoint correction on the GNSS IWV trend estimates is then evaluated. Numéro de notice : C2022-009 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComSansActesPubliés-Unpublished DOI : 10.5194/egusphere-egu22-6390 En ligne : https://doi.org/10.5194/egusphere-egu22-6390 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100713

Near-real-time identification of the drivers of deforestation in French Guiana / Marie Ballère (2021)  

Public Titre : Near-real-time identification of the drivers of deforestation in French Guiana Type de document : Article/Communication Auteurs : Marie Ballère , Auteur ; Stéphane Mermoz, Auteur ; Alexandre Bouvet, Auteur ; Thierry Koleck, Auteur Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2021 Conférence : EGU 2021, General Assembly 19/04/2021 30/04/2021 en ligne Autriche OA Abstracts only Format : 21 x 30 cm Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] déboisement [Termes IGN] exploitation forestière [Termes IGN] forêt tropicale [Termes IGN] Guyane (département français) [Termes IGN] image radar moirée [Termes IGN] image Sentinel-SAR [Termes IGN] mine d'or [Termes IGN] surveillance forestière [Termes IGN] urbanisation Numéro de notice : C2021-004 Affiliation des auteurs : UGE-LASTIG+Ext (2020- ) Thématique : BIODIVERSITE/FORET/IMAGERIE Nature : Communication nature-HAL : ComSansActesPubliés-Unpublished DOI : sans En ligne : https://doi.org/10.5194/egusphere-egu21-16015 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97598

Precipitation frequency in MED and EURO-CORDEX ensembles from 0.44° to convective permitting resolution: what explains the differences? / Minh Ha-Truong (2021)  

Public Titre : Precipitation frequency in MED and EURO-CORDEX ensembles from 0.44° to convective permitting resolution: what explains the differences? Type de document : Article/Communication Auteurs : Minh Ha-Truong, Auteur ; Sophie Bastin, Auteur ; Philippe Drobinski, Auteur ; Lluis Fita, Auteur ; Marjolaine Chiriaco, Auteur ; Jan Polcher, Auteur ; Olivier Bock , Auteur Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2021 Conférence : EGU 2021, General Assembly 19/04/2021 30/04/2021 en ligne Autriche OA Abstracts only Importance : 1 p. Format : 21 x 30 cm Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] bassin méditerranéen [Termes IGN] convection [Termes IGN] données météorologiques [Termes IGN] Europe (géographie politique) [Termes IGN] modèle atmosphérique [Termes IGN] orographie [Termes IGN] précipitation [Termes IGN] teneur intégrée en vapeur d'eau Numéro de notice : C2021-001 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComSansActesPubliés-Unpublished DOI : sans En ligne : https://meetingorganizer.copernicus.org/EGU21/EGU21-8843.html Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97582

Sensitivity of segmentation of GNSS IWV time series and trend estimates to data properties / Khanh Ninh Nguyen (2021)  

Public Titre : Sensitivity of segmentation of GNSS IWV time series and trend estimates to data properties Type de document : Article/Communication Auteurs : Khanh Ninh Nguyen, Auteur ; Annarosa Quarello , Auteur ; Olivier Bock , Auteur ; Emilie Lebarbier, Auteur Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2021 Conférence : EGU 2021, General Assembly 19/04/2021 30/04/2021 en ligne Autriche OA Abstracts only Format : 21 x 30 cm Langues : Anglais (eng) Descripteur : [Termes IGN] analyse de sensibilité [Termes IGN] données GNSS [Termes IGN] segmentation [Termes IGN] série temporelle [Termes IGN] teneur intégrée en vapeur d'eau [Vedettes matières IGN] Traitement de données GNSS Numéro de notice : C2021-003 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComSansActesPubliés-Unpublished DOI : sans En ligne : https://doi.org/10.5194/egusphere-egu21-16099https://doi.org/10.5194/egusphere-e [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97597

IWV retrieval from ground and shipborne GPS receivers during NAWDEX [diaporama] / Pierre Bosser (2020)  

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IWV retrieval from shipborne GPS receiver on hydrographic ship Borda [diaporama] / Olivier Bock (2020)  

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GRACE gravitational signature of the 2011 Mw 9.0 Tohoku-oki earthquake / Isabelle Panet (2018)

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ITRF and seasonal station motions / Zuheir Altamimi (2018)

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ITRF2014 and Earth figure changes: evidence of global viscous relaxation in recent ice melting Earth’s response? / Laurent Métivier (2018)

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Mass redistributions of the 2011 Mw 9.0 Tohoku-oki earthquake from GRACE / Isabelle Panet (2018)

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Optimization of atomic clock locations for the geopotential determination from gravimetric network / Guillaume Lion (2018)

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Spatial correlations in IGS station position time series / Clément Benoist (2018)

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Towards a realistic spatio-temporal description of GNSS station position time series / Paul Rebischung (2018)

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Clock measurements to improve the geopotential determination / Guillaume Lion (2017)    

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