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Effects of space weather on GOCE electrostatic gravity gradiometer measurements / Elmas Sinem Ince in Journal of geodesy, vol 90 n° 12 (December 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 12 (December 2016) . - pp 1389 - 1403 Titre : Effects of space weather on GOCE electrostatic gravity gradiometer measurements Type de document : Article/Communication Auteurs : Elmas Sinem Ince, Auteur ; Spiros D. Pagiatakis, Auteur Année de publication : 2016 Article en page(s) : pp 1389 - 1403 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] champ magnétique local [Termes IGN] géophysique externe [Termes IGN] gradient de gravitation [Termes IGN] gradiomètre [Termes IGN] perturbation ionosphérique [Termes IGN] pôle Résumé : (Auteur) We examine the presence of residual nongravitational signatures in gravitational gradients measured by GOCE electrostatic gravity gradiometer. These signatures are observed over the magnetic poles during geomagnetically active days and can contaminate the trace of the gravitational gradient tensor by up to three to five times the expected noise level of the instrument (∼11 mE). We investigate these anomalies in the gradiometer measurements along many satellite tracks and examine possible causes using external datasets, such as interplanetary electric field measurements from the ACE (advanced composition explorer) and WIND spacecraft, and Poynting vector (flux) estimated from equivalent ionospheric currents derived from spherical elementary current systems over North America and Greenland. We show that the variations in the east-west and vertical electrical currents and Poynting vector components at the satellite position are highly correlated with the disturbances observed in the gradiometer measurements. The results presented in this paper reveal that the disturbances are due to intense ionospheric current variations that are enhanced by increased solar activity that causes a very dynamic drag environment. Moreover, successful modelling and removal of a high percentage of these disturbances are possible using external geomagnetic field observations. Numéro de notice : A2016-809 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0931-8 En ligne : http://dx.doi.org/10.1007/s00190-016-0931-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82601 [article]

Geophysical methods for CO2 plume imaging: Comparison of performances / H. Fabriol in Energy Procedia, vol 4 ([01/02/2011])  

Public [article]  inEnergy Procedia > vol 4 [01/02/2011] Titre : Geophysical methods for CO2 plume imaging: Comparison of performances Type de document : Article/Communication Auteurs : H. Fabriol, Auteur ; A. Bitri, Auteur ; B. Bourgeois, Auteur ; M. Delatre, Auteur ; J.F. Girard, Auteur ; Gwendoline Pajot-Métivier , Auteur ; J. Rohmer, Auteur Année de publication : 2011 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] dioxyde de carbone [Termes IGN] géophysique externe Résumé : (auteur) Geophysical methods are adequate for imaging the CO2 plume in order to follow its migration within the reservoir and possible leakages through the caprock formation. In particular, changes in density, seismic velocity or electrical resistivity are associated with changes in the gas saturation and make methods such as gravity, 4D seismic and electrical resistivity tomography (ERT) or CSEM powerful tools to follow up the fate of injected CO2. Respect to the minimum amount of CO2 stored that can be quantified for verification purpose, there is an order of magnitude between 4D seismic (few 100s of Kt) and the other two methods (few Mt). Respect to the detection of leakage at the reservoir level, only 4D seismic could be considered as useful. Using downhole measurements, such as crosshole electric or downhole gravity will increase the resolution of these methods and therefore its ability to detect leakage. In case of CO2 leakage upwards and accumulation within a secondary reservoir located at a few hundreds of meters depth, the resolution of the three methods is increased by several order of magnitude and small amounts of CO2 could be detected, depending whether it is in gaseous phase or dissolved. It is expected that controlled experiments of leaking CO2 at shallow depth will help to define more precisely the conditions of use of the three methods. Numéro de notice : A2011-631 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.egypro.2011.02.290 En ligne : https://doi.org/10.1016/j.egypro.2011.02.290 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101408 [article]

Electromagnetic wave scattering from the sea surface in the presence of wind wave patterns / V. Shrira in International Journal of Remote Sensing IJRS, vol 24 n° 24 (December 2003)  

Public [article]  inInternational Journal of Remote Sensing IJRS > vol 24 n° 24 (December 2003) . - pp 5075 - 5093 Titre : Electromagnetic wave scattering from the sea surface in the presence of wind wave patterns Type de document : Article/Communication Auteurs : V. Shrira, Auteur ; S.I. Badulin, Auteur ; A.G. Voronovich, Auteur Année de publication : 2003 Article en page(s) : pp 5075 - 5093 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] analyse harmonique [Termes IGN] formule de Stokes [Termes IGN] géophysique externe [Termes IGN] interférence [Termes IGN] mer [Termes IGN] onde électromagnétique [Termes IGN] surface de la mer [Termes IGN] vent Résumé : (Auteur) The study is concerned with electromagnetic wave (EM) scattering by a random sea surface in the presence of coherent wave patterns. The coherent patterns are understood in a broad sense as the existence of certain dynamical coupling between linear Fourier components of the water wave field. We show that the presence of weakly nonlinear wave patterns can significantly change the EM scattering compared to the case of a completely random wave field. Generalizing the Random Phase Approximation (RPA) we suggest a new paradigm for EM scattering by a random sea surface. The specific analysis carried out in the paper synthesizes the small perturbation method for EM scattering and a weakly nonlinear approach for wind wave dynamics. By investigating, in detail, two examples of a random sea surface composed of either Stokes waves or horse-shoe ('crescent-shaped') patterns the mechanism of the pattern effect on scattering is revealed. Each Fourier harmonic of the scattered EM field is found to be a sum of contributions due to different combinations of wave field harmonics. Among these 'partial scatterings' there are phase-dependent ones and, therefore, the intensity of the resulting EM harmonic is sensitive to the phase relations between the wind wave harmonics. The effect can be interpreted as interference of partial scatterings due to the coexistence of several phase-related periodic scattering grids. A straightforward generalization of these results enables us to obtain, for a given wind wave field and an incident EM field, an a priori estimate of whether the effects due to the patterns are significant and the commonly used RPA is inapplicable. When the RPA is inapplicable, we suggest its natural generalization by re-defining the statistical ensemble for water surface. First, EM scattering by an 'elementary' constituent pattern should be considered. Each such scattering is affected by the interference because the harmonics comprising the pattern are dynamically linked. Then, ensemble averaging, which takes into account the distribution of the pattern parameters (based on the assumption that the phases between the patterns are random), should be carried out. It is shown that, generally, this interference does not vanish for any statistical ensemble due to dynamical coupling between water wave harmonics. The suggest RPA genralization takes into account weak non-Gaussianity of water wave field in contrast to the traditional RPA which ignores it. Numéro de notice : A2003-339 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/0143116031000095907 En ligne : https://doi.org/10.1080/0143116031000095907 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22634 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
080-03241	RAB	Revue	Centre de documentation	En réserve L003	Exclu du prêt

Global structure of marine wind speed variability derived from Topex altimeter data / G. Chen in International Journal of Remote Sensing IJRS, vol 24 n° 24 (December 2003)  

Public [article]  inInternational Journal of Remote Sensing IJRS > vol 24 n° 24 (December 2003) . - pp 5119 - 5133 Titre : Global structure of marine wind speed variability derived from Topex altimeter data Type de document : Article/Communication Auteurs : G. Chen, Auteur ; S.W. Bi, Auteur ; J. Ma, Auteur Année de publication : 2003 Article en page(s) : pp 5119 - 5133 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] climat terrestre [Termes IGN] courant aérien [Termes IGN] données altimétriques [Termes IGN] données Topex-Poseidon [Termes IGN] géophysique externe [Termes IGN] océanographie spatiale [Termes IGN] Pacifique (océan) [Termes IGN] surface de la mer [Termes IGN] vague [Termes IGN] vent Résumé : (Auteur) As the largest source of momentum for the ocean surface, wind affects the full range, of oceanic motion-from individual surface waves to complete current systems. The marine surface wind is among the critical geophysical parameters which determine the most fundamental aspects of the ocean. Using six years (1993-1998) of TOPEX altimeter data with an unprecedented accuracy and continuity, a detailed investigation of the global structure of marine wind climatology and variability is carried out. It is found that the overall pattern of wind climatology is basically determined by solar radiation and therefore dominated by zonal features, while that of the wind variability is largely 'event' determined and thereby dominated by regional features. Consequently, wind climatology and wind variability show a complex relationship in their magnitude of intensity. Strong winds may be associated with high variabilities, such as in the westerlies of the North Atlantic and North Pacific; they may also be associated with low variabilities, such as in the westerlies of the Southern Ocean. Meanwhile, weak wind zones like the doldrums in the western equatorial Pacific can have a very low level of annual variability, while a very high level of interannual variability. The Asian monsoon system has a lower than average climatological mean speed, but exhibits extremely high annual variability. The phase distributions of wind variations carry combined information of climatology and variability. Effects of the Asian monsoon and marine storms are manifested on top of the basically zonal phase pattern. Statistics suggest that semiannual variability exceeds annual variability for 12.2% of the world's oceans, and interannual variability exceeds annual variability for 26.4% of the world's oceans. Numéro de notice : A2003-340 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/0143116031000082091 En ligne : https://doi.org/10.1080/0143116031000082091 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22635 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
080-03241	RAB	Revue	Centre de documentation	En réserve L003	Exclu du prêt

Comparison of interannual intrinsic modes in hemispheric sea ice covers and other geophysical parameters / P. Gloersen in IEEE Transactions on geoscience and remote sensing, vol 41 n° 5 (May 2003)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 41 n° 5 (May 2003) . - pp 1062 - 1074 Titre : Comparison of interannual intrinsic modes in hemispheric sea ice covers and other geophysical parameters Type de document : Article/Communication Auteurs : P. Gloersen, Auteur ; N. Huang, Auteur Année de publication : 2003 Article en page(s) : pp 1062 - 1074 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Télédétection [Termes IGN] analyse comparative [Termes IGN] Antarctique [Termes IGN] banquise [Termes IGN] géophysique externe [Termes IGN] glace de mer [Termes IGN] mesurage de la fréquence [Termes IGN] oscillation [Termes IGN] télédétection spatiale [Termes IGN] transformation de Fourier Résumé : (Auteur) Recent papers have described 18year trends and interannual oscillations in the Arctic and Antarctic sea ice extents, areas, and enclosed open water areas based on newly formulated 18.2year ice concentration time series. They were obtained by finetuning the sea ice algorithm tie points individually for each of the four sensors used to acquire the data. In this paper, these analyses are extended to an examination of the intrinsic modes of these time series, obtained by means of empirical mode decomposition, which handles both nonstationary and nonlinear data as found in these time series, unlike filtering techniques based on Fourier analysis. Our analysis centers on periodicities greater than one year. Quasibiennial and quasiquadrennial oscillations similar to those observed earlier with a multitaperfiltered Fourier analysis technique were also observed here. The intrinsic modes described here feature frequency as well as amplitude modulation within their respective frequency bands. The slowest varying mode in the Antarctic sea ice cover has slightly less than a full period during this 18.2year time period, but the change in sign of its curvature hints at a modal period of about 19 years, with important implications for the trend analyses published earlier. Numéro de notice : A2003-206 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2003.811814 En ligne : https://doi.org/10.1109/TGRS.2003.811814 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22502 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
065-03051	RAB	Revue	Centre de documentation	En réserve L003	Disponible