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Assimilation of GRACE-derived oceanic mass distributions with a global ocean circulation model / J. Saynisch in Journal of geodesy, vol 89 n° 2 (February 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 2 (February 2015) . - pp 121 - 139 Titre : Assimilation of GRACE-derived oceanic mass distributions with a global ocean circulation model Type de document : Article/Communication Auteurs : J. Saynisch, Auteur ; I. Bergmann–Wolf, Auteur ; M. Thomas, Auteur Année de publication : 2015 Article en page(s) : pp 121 - 139 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] anomalie de pesanteur [Termes IGN] assimilation des données [Termes IGN] champ de pesanteur terrestre [Termes IGN] correction atmosphérique [Termes IGN] données GRACE [Termes IGN] filtre de Kalman [Termes IGN] masse d'eau [Termes IGN] océan [Termes IGN] océanographie spatiale Résumé : (auteur) To study the sub-seasonal distribution and generation of ocean mass anomalies, Gravity Recovery and Climate Experiment (GRACE) observations of daily and monthly resolution are assimilated into a global ocean circulation model with an ensemble-based Kalman-Filter technique. The satellite gravimetry observations are processed to become time-variable fields of ocean mass distribution. Error budgets for the observations and the ocean model’s initial state are estimated which contain the full covariance information. The consistency of the presented approach is demonstrated by increased agreement between GRACE observations and the ocean model. Furthermore, the simulations are compared with independent observations from 54 bottom pressure recorders. The assimilation improves the agreement to high-latitude recorders by up to 2 hPa. The improvements are caused by assimilation-induced changes in the atmospheric wind forcing, i.e., quantities not directly observed by GRACE. Finally, the use of the developed Kalman-Filter approach as a destriping filter to remove artificial noise contaminating the GRACE observations is presented Numéro de notice : A2015-332 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0766-0 Date de publication en ligne : 11/10/2014 En ligne : https://doi.org/10.1007/s00190-014-0766-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76657 [article]

Updating ESA’s Earth System Model for Gravity Mission Simulation Studies, 2. Comparison with the Original Model / I. Bergmann–Wolf (2014) 

Public Titre de série : Updating ESA’s Earth System Model for Gravity Mission Simulation Studies, 2 Titre : Comparison with the Original Model Type de document : Rapport Auteurs : I. Bergmann–Wolf, Auteur ; Robert Dill, Auteur ; E. Forootan, Auteur ; et al., Auteur Editeur : Postdam : GeoForschungsZentrum Postdam Année de publication : 2014 Collection : Scientific technical reports num. 14-08 Importance : 60 p. Format : 21 x 30 cm Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] calotte glaciaire [Termes IGN] champ de pesanteur terrestre [Termes IGN] marée océanique [Termes IGN] masse d'air [Termes IGN] variabilité Résumé : (auteur) The ability of any satellite gravity mission concept to monitor mass transport processes in the Earth system is typically tested well ahead of its implementation by means of various simulation studies. Those studies often extend from the simulation of realistic orbits and instrumental data all the way down to the retrieval of global gravity field solution time-series. Basic requirement for all these simulations are realistic representations of the spatio-temporal mass variability in the different sub-systems of the Earth, as a source model for the orbit computations. For such simulations, a suitable source model is required to represent (i) high-frequency (i.e., sub-daily to weekly) mass variability in the atmosphere and oceans, in order to realistically include the effects of temporal aliasing due to non-tidal high-frequency mass variability into the retrieved gravity fields. In parallel, (ii) low-frequency (i.e., monthly to interannual) variability needs to be modelled with realistic amplitudes, particularly at small spatial scales, in order to assess to what extent a new mission concept might provide further insight into physical processes currently not observable. The new source model documented here attempts to fulfil both requirements: Based on ECMWF’s recent atmospheric reanalysis ERA-Interim and corresponding simulations from numerical models of the other Earth system components, it offers spherical harmonic coefficients of the time-variable global gravity field due to mass variability in atmosphere, oceans, the terrestrial hydrosphere including the ice-sheets and glaciers, as well as the solid Earth. Simulated features range from sub-daily to multiyear periods with a spatial resolution of spherical harmonics degree and order 180 over a period of 12 years. In addition to the source model, a de-aliasing model for atmospheric and oceanic high-frequency variability with augmented systematic and random noise is required for a realistic simulation of the gravity field retrieval process, whose necessary error characteristics are discussed. The documentation is organized as follows: The characteristics of the updated ESM along with some basic validation are presented in Volume 1 of this report (Dobslaw et al., 2014). A detailed comparison to the original ESA ESM (Gruber et al., 2011) is provided in Volume 2 (Bergmann-Wolf et al., 2014), while Volume 3 (Forootan et al., 2014) contains a description of the strategy to derive a realistically noisy de-aliasing model for the high-frequency mass variability in atmosphere and oceans. Numéro de notice : 16183 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Rapport d'étude technique Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75978

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