Short-arc analysis of intersatellite tracking data in a gravity mapping mission   总被引：1，自引：0，他引：1  

D. D. Rowlands  R. D. Ray  D. S. Chinn  F. G. Lemoine 《Journal of Geodesy》2002,76(6-7):307-316

 A technique for the analysis of low–low intersatellite range-rate data in a gravity mapping mission is explored. The technique is based on standard tracking data analysis for orbit determination but uses a spherical coordinate representation of the 12 epoch state parameters describing the baseline between the two satellites. This representation of the state parameters is exploited to allow the intersatellite range-rate analysis to benefit from information provided by other tracking data types without large simultaneous multiple-data-type solutions. The technique appears especially valuable for estimating gravity from short arcs (e.g. less than 15 minutes) of data. Gravity recovery simulations which use short arcs are compared with those using arcs a day in length. For a high-inclination orbit, the short-arc analysis recovers low-order gravity coefficients remarkably well, although higher-order terms, especially sectorial terms, are less accurate. Simulations suggest that either long or short arcs of the Gravity Recovery and Climate Experiment (GRACE) data are likely to improve parts of the geopotential spectrum by orders of magnitude. Received: 26 June 2001 / Accepted: 21 January 2002  相似文献   

ESR chronology of the Somme River Terrace system and first human settlements in Northern France   总被引：1，自引：0，他引：1  

Jean-Jacques Bahain  Christophe Falgures  Michel Laurent  Pierre Voinchet  Jean-Michel Dolo  Pierre Antoine  Alain Tuffreau 《Quaternary Geochronology》2007,2(1-4):356-362

The Somme Valley, Northern France, is famous for its archaeological sequence, where numerous rich Palaeolithic sites, such as Saint-Acheul, the type site of the Acheulian, have been discovered. The archaeological levels are often directly associated with fossil alluvial sediments of the River Somme or with slope deposits, including loess and palaeosols. In the middle reaches of the valley, near Amiens, the system of fossil-stepped fluvial terraces is particularly well developed and preserved, and occurs on 10 alluvial formations. These terraces, from +5 to +55 m above the present-day valley bedrock, allow the study of the environmental changes and the human settlement of this area through the Pleistocene.

Since 1988, ESR dating was systematically applied on bleached quartz extracted from the fossil fluvial deposits, in order to better describe the geological evolution of the stepped system. More recently, U-series/ESR dating has also been performed on teeth collected from the different terrace deposits. Here we present a synthetic review of the main ESR results, and propose an ESR chronology for the geological evolution of the Somme fluvial system and for the Middle Pleistocene human settlement of northern France.  相似文献   

Influence of the oceanic biology on the tropical Pacific climate in a coupled general circulation model   总被引：1，自引：3，他引：1  

Matthieu Lengaigne  Christophe Menkes  Olivier Aumont  Thomas Gorgues  Laurent Bopp  Jean-Michel André  Gurvan Madec 《Climate Dynamics》2007,28(5):503-516

The influence of chlorophyll spatial patterns and variability on the tropical Pacific climate is investigated by using a fully coupled general circulation model (HadOPA) coupled to a state-of-the-art biogeochemical model (PISCES). The simulated chlorophyll concentrations can feedback onto the ocean by modifying the vertical distribution of radiant heating. This fully interactive biological-ocean-atmosphere experiment is compared to a reference experiment that uses a constant chlorophyll concentration (0.06 mg m⁻³). It is shown that introducing an interactive biology acts to warm the surface eastern equatorial Pacific by about 0.5°C. Two competing processes are involved in generating this warming: (a) a direct 1-D biological warming process in the top layers (0–30 m) resulting from strong chlorophyll concentrations in the upwelling region and enhanced by positive dynamical feedbacks (weaker trade winds, surface currents and upwelling) and (b) a 2-D meridional cooling process which brings cold off-equatorial anomalies from the subsurface into the equatorial mixed layer through the meridional cells. Sensitivity experiments show that the climatological horizontal structure of the chlorophyll field in the upper layers is crucial to maintain the eastern Pacific warming. Concerning the variability, introducing an interactive biology slightly reduces the strength of the seasonal cycle, with stronger SST warming and chlorophyll concentrations during the upwelling season. In addition, ENSO amplitude is slightly increased. Similar experiments performed with another coupled general circulation model (IPSL-CM4) exhibit the same behaviour as in HadOPA, hence showing the robustness of the results.  相似文献   

Mise en évidence d'un mécanisme de carbonatation secondaire dans le manteau supérieur du Languedoc     

Jean-Marie Dautria  Delphine Bosch  Jean-Michel Liotard 《Comptes Rendus Geoscience》2006,338(8):527-536

Lherzolite xenoliths with calcite-rich microgranular secondary aggregates (0.1–1 mm) have been sampled in a Messinian breccia pipe from the northeastern part of the Languedoc volcanic province (South France). Their study shows that the carbonate crystallized at low pressure from a silico-carbonated melt resulting from partial melting of diopside and spinel at depth. This melting has been induced by injection, shortly before the eruption, of CO₂ and H₂O-rich fluids, stored probably within the upper lithospheric mantle and reset in motion by the magma ascension. These fluids would derive from decarbonation of levels of deeper lithospheric mantle previously metasomatized by carbonatitic melts. To cite this article: J.-M. Dautria et al., C. R. Geoscience 338 (2006).  相似文献   

Disjunctive kriging: Comparison of theory with actual results     

Jean-Michel Rendu 《Mathematical Geology》1980,12(4):305-320

  相似文献   

Estimated SLR station position and network frame sensitivity to time-varying gravity   总被引：1，自引：1，他引：0  

Nikita P. Zelensky  Frank G. Lemoine  Douglas S. Chinn  Stavros Melachroinos  Brian D. Beckley  Jennifer Wiser Beall  Oleg Bordyugov 《Journal of Geodesy》2014,88(6):517-537

This paper evaluates the sensitivity of ITRF2008-based satellite laser ranging (SLR) station positions estimated weekly using LAGEOS-1/2 data from 1993 to 2012 to non-tidal time-varying gravity (TVG). Two primary methods for modeling TVG from degree-2 are employed. The operational approach applies an annual GRACE-derived field, and IERS recommended linear rates for five coefficients. The experimental approach uses low-order/degree $4\times 4$ coefficients estimated weekly from SLR and DORIS processing of up to 11 satellites (tvg4x4). This study shows that the LAGEOS-1/2 orbits and the weekly station solutions are sensitive to more detailed modeling of TVG than prescribed in the current IERS standards. Over 1993–2012 tvg4x4 improves SLR residuals by 18 % and shows 10 % RMS improvement in station stability. Tests suggest that the improved stability of the tvg4x4 POD solution frame may help clarify geophysical signals present in the estimated station position time series. The signals include linear and seasonal station motion, and motion of the TRF origin, particularly in Z. The effect on both POD and the station solutions becomes increasingly evident starting in 2006. Over 2008–2012, the tvg4x4 series improves SLR residuals by 29 %. Use of the GRGS RL02 $50\times 50$ series shows similar improvement in POD. Using tvg4x4, secular changes in the TRF origin Z component double over the last decade and although not conclusive, it is consistent with increased geocenter rate expected due to continental ice melt. The test results indicate that accurate modeling of TVG is necessary for improvement of station position estimation using SLR data.  相似文献   

Orbit determination of the SELENE satellites using multi-satellite data types and evaluation of SELENE gravity field models   总被引：1，自引：0，他引：1  

S. Goossens  K. Matsumoto  D. D. Rowlands  F. G. Lemoine  H. Noda  H. Araki 《Journal of Geodesy》2011,85(8):487-504

The SELENE mission, consisting of three separate satellites that use different terrestrial-based tracking systems, presents a unique opportunity to evaluate the contribution of these tracking systems to orbit determination precision. The tracking data consist of four-way Doppler between the main orbiter and one of the two sub-satellites while the former is over the far side, and of same-beam differential VLBI tracking between the two sub-satellites. Laser altimeter data are also used for orbit determination. The contribution to orbit precision of these different data types is investigated through orbit overlap analysis. It is shown that using four-way and VLBI data improves orbit consistency for all satellites involved by reducing peak values in orbit overlap differences that exist when only standard two-way Doppler and range data are used. Including laser altimeter data improves the orbit precision of the SELENE main satellite further, resulting in very smooth total orbit errors at an average level of 18 m. The multi-satellite data have also resulted in improved lunar gravity field models, which are assessed through orbit overlap analysis using Lunar Prospector tracking data. Improvements over a pre-SELENE model are shown to be mostly in the along-track and cross-track directions. Orbit overlap differences are at a level between 13 and 21 m with the SELENE models, depending on whether 1-day data overlaps or 1-day predictions are used.  相似文献   

The carbon dioxide solubility in alkali basalts: an experimental study   总被引：1，自引：1，他引：0  

Priscille Lesne  Bruno Scaillet  Michel Pichavant  Jean-Michel Beny 《Contributions to Mineralogy and Petrology》2011,162(1):153-168

Experiments were conducted to determine CO₂ solubilities in alkali basalts from Vesuvius, Etna and Stromboli volcanoes. The basaltic melts were equilibrated with nearly pure CO₂ at 1,200°C under oxidizing conditions and at pressures ranging from 269 to 2,060 bars. CO₂ solubility was determined by FTIR measurements. The results show that alkalis have a strong effect on the CO₂ solubility and confirm and refine the relationship between the compositional parameter Π devised by Dixon (Am Mineral 82:368–378, 1997) and the CO₂ solubility. A general thermodynamic model for CO₂ solubility in basaltic melts is defined for pressures up to 2 kbars. Based on the assumption that O²⁻ and CO₃²⁻ mix ideally, we have:

_boxclose_3^2 - ^m (P,T)X_^2 - ^m f__2 (P,T) K(P,T) = X__3^2 - ^m (P,T) ( X_^2 - ^m f__2 (P,T) ). \begin{gathered} K(P,T) = {\frac{{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)}}{{X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)}}} \hfill \\ K(P,T) = {{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)} \mathord{\left/ {\vphantom {{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)} {\left( {X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)} \right).}}} \right. \kern-\nulldelimiterspace} {\left( {X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)} \right).}} \hfill \\ \end{gathered}  相似文献    49. Investigating the hydromechanical behaviour of bentonite pellets by swelling pressure tests and discrete element modelling      Darde  Benjamin  Roux  Jean-Noël  Pereira  Jean-Michel  Dangla  Patrick  Talandier  Jean  Vu  Minh Ngoc  Tang  Anh Minh 《Acta Geotechnica》2021,16(2):507-524 Acta Geotechnica - Bentonite pellet mixtures are candidate material for the sealing of galleries in radioactive waste disposals. The hydromechanical behaviour of assemblies of bentonite pellets is...  相似文献    50. Spatial quick-clay predictions using multi-criteria evaluation in SW Sweden      M. A. Persson  R. L. Stevens  Å. Lemoine 《Landslides》2014,11(2):263-279 The transformation of marine and glaciomarine clay deposits into high sensitive and quick clays is largely dependent on the influence of local and regional geologic history and the resulting stratigraphy. The general conditions that facilitate quick-clay development are well known from numerous laboratory investigations during the last century, but their local and regional in-field variation is less understood. In this study, the geographic distribution of quick clay in SW Sweden is predicted using a multicriteria evaluation model that incorporates both qualitative information (established theory and expert judgment concerning the influences on both quick-clay development and the stratigraphic and geomorphologic distribution of sediment types) and observational data (maps of surficial deposits, geotechnical records and digital elevation data). This information duality cannot be avoided if knowledge from different disciplines is utilized. Considering this, model transparency is important for improvements and for characterizing its reliability for risk analysis. The model was constructed stepwise by an initial parameterization with subsequent hierarchical structuring, weighting and standardization of criteria, before running the full analysis. Comparisons between regional model results and geotechnically documented localities have yielded promising results concerning the model’s ability to predict general trends. However, the large natural and site-specific variability of clay sensitivities is not always captured by the model. These deviations are examined and suggestions are given for minimizing their effect. Applications of model methodology and results are briefly discussed.  相似文献    [首页] « 上一页 [1] [2] [3] [4] 5 [6] [7] [8] [9] [10] [11] 下一页 » 末  页»