Estimation of phase center corrections for GLONASS-M satellite antennas   总被引：3，自引：3，他引：0  

Florian Dilssner  Tim Springer  Claudia Flohrer  John Dow 《Journal of Geodesy》2010,84(8):467-480

Driven by the comprehensive modernization of the GLONASS space segment and the increased global availability of GLONASS-capable ground stations, an updated set of satellite-specific antenna phase center corrections for the current GLONASS-M constellation is determined by processing 84 weeks of dual-frequency data collected between January 2008 and August 2009 by a worldwide network of 227 GPS-only and 115 combined GPS/GLONASS tracking stations. The analysis is performed according to a rigorous combined multi-system processing scheme providing full consistency between the GPS and the GLONASS system. The solution is aligned to a realization of the International Terrestrial Reference Frame 2005. The estimated antenna parameters are compared with the model values currently used within the International GNSS Service (IGS). It is shown that the z-offset estimates are on average 7 cm smaller than the corresponding IGS model values and that the block-specific mean value perfectly agrees with the nominal GLONASS-M z-offset provided by the satellite manufacturer. The existence of azimuth-dependent phase center variations is investigated and uncertainties in the horizontal offset estimates due to mathematical correlations and yaw-attitude modeling problems during eclipse seasons are addressed. Finally, it is demonstrated that the orbit quality benefits from the updated GLONASS-M antenna phase center model and that a consistent set of satellite antenna z-offsets for GPS and GLONASS is imperative to obtain consistent GPS- and GLONASS-derived station heights.  相似文献   

Calcium isotope fractionation in modern scleractinian corals     

Florian Böhm  Nikolaus Gussone  Anton Eisenhauer  Stéphanie Reynaud 《Geochimica et cosmochimica acta》2006,70(17):4452-4462

The ⁴⁴Ca/⁴⁰Ca ratios of cultured (Acropora sp.) and open ocean (Pavona clavus, Porites sp.) tropical reef corals are positively correlated with growth temperature. The slope of the temperature-fractionation relation is similar to inorganic aragonite precipitates. However, δ^44/40Ca of the coral aragonite is offset from inorganic and sclerosponge aragonite by about +0.5‰. This offset can neither be explained by the very fast, biologically controlled calcification of scleractinian corals, nor as a consequence of calcification from a partly closed volume of fluid. As corals actively transport calcium through several cell layers to the site of calcification, the most likely explanation for the offset is a biologically induced fractionation. Our results indicate a limited use of Ca isotopes in scleractinian corals as temperature proxy.  相似文献   

A deglaciation model of the Oberhasli,Switzerland          下载免费PDF全文

Christian Wirsig  Jerzy Zasadni  Susan Ivy‐Ochs  Marcus Christl  Florian Kober  Christian Schlüchter 《第四纪科学杂志》2016,31(1):46-59

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Towards a cross-domain interoperable framework for natural hazards and disaster risk reduction information     

Robert Tomas  Matthew Harrison  José I. Barredo  Florian Thomas  Miguel Llorente Isidro  Manuela Pfeiffer  Otakar Čerba 《Natural Hazards》2015,78(3):1545-1563

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Stratigraphy and Mesozoic–Cenozoic tectonic history of northern Sierra Los Ajos and adjacent areas,Sonora, Mexico     

William R. Page  Floyd Gray  Alexander Iriondo  Daniel Miggins  Robert B. Blodgett  Florian Maldonado  Robert J. Miller 《Journal of South American Earth Sciences》2010,29(3):557-571

Geologic mapping in the northern Sierra Los Ajos reveals new stratigraphic and structural data relevant to deciphering the Mesozoic–Cenozoic tectonic evolution of the range. The northern Sierra Los Ajos is cored by Proterozoic, Cambrian, Devonian, Mississippian, and Pennsylvanian strata, equivalent respectively to the Pinal Schist, Bolsa Quartzite and Abrigo Limestone, Martin Formation, Escabrosa Limestone, and Horquilla Limestone. The Proterozoic–Paleozoic sequence is mantled by Upper Cretaceous rocks partly equivalent to the Fort Crittenden and Salero Formations in Arizona, and the Cabullona Group in Sonora, Mexico.Absence of the Upper Jurassic–Lower Cretaceous Bisbee Group below the Upper Cretaceous rocks and above the Proterozoic–Paleozoic rocks indicates that the Sierra Los Ajos was part of the Cananea high, a topographic highland during the Late Jurassic and Early Cretaceous. Deposition of Upper Cretaceous rocks directly on Paleozoic and Proterozoic rocks indicates that the Sierra Los Ajos area had subsided as part of the Laramide Cabullona basin during Late Cretaceous time. Basal beds of the Upper Cretaceous sequence are clast-supported conglomerate composed locally of basement (Paleozoic) clasts. The conglomerate represents erosion of Paleozoic basement in the Sierra Los Ajos area coincident with development of the Cabullona basin.The present-day Sierra Los Ajos reaches elevations of greater than 2600 m, and was uplifted during Tertiary basin-and-range extension. Upper Cretaceous rocks are exposed at higher elevations in the northern Sierra Los Ajos and represent an uplifted part of the inverted Cabullona basin. Tertiary uplift of the Sierra Los Ajos was largely accommodated by vertical movement along the north-to-northwest-striking Sierra Los Ajos fault zone flanking the west side of the range. This fault zone structurally controls the configuration of the headwaters of the San Pedro River basin, an important bi-national water resource in the US-Mexico border region.  相似文献   

Probabilistic collocation and lagrangian sampling for advective tracer transport in randomly heterogeneous porous media     

Florian Müller  Patrick JennyDaniel W. Meyer 《Advances in water resources》2011,34(12):1527-1538

The Karhunen-Loeve (KL) decomposition and the polynomial chaos (PC) expansion are elegant and efficient tools for uncertainty propagation in porous media. Over recent years, KL/PC-based frameworks have successfully been applied in several contributions for the flow problem in the subsurface context. It was also shown, however, that the accurate solution of the transport problem with KL/PC techniques is more challenging. We propose a framework that utilizes KL/PC in combination with sparse Smolyak quadrature for the flow problem only. In a subsequent step, a Lagrangian sampling technique is used for transport. The flow field samples are calculated based on a PC expansion derived from the solutions at relatively few quadrature points. To increase the computational efficiency of the PC-based flow field sampling, a new reduction method is applied. For advection dominated transport scenarios, where a Lagrangian approach is applicable, the proposed PC/Monte Carlo method (PCMCM) is very efficient and avoids accuracy problems that arise when applying KL/PC techniques to both flow and transport. The applicability of PCMCM is demonstrated for transport simulations in multivariate Gaussian log-conductivity fields that are unconditional and conditional on conductivity measurements.  相似文献   

Sources of fluids and gases expelled at cold seeps offshore Georgia, eastern Black Sea   总被引：1，自引：0，他引：1  

Anja Reitz  Thomas Pape  Mark Schmidt  Florian Scholz  Giovanni Aloisi  Stephan M. Weise 《Geochimica et cosmochimica acta》2011,75(11):3250-46

Four seep sites located within an ∼20 km² area offshore Georgia (Batumi seep area, Pechori Mound, Iberia Mound, and Colkheti Seep) show characteristic differences with respect to element concentrations, and oxygen, hydrogen, strontium, and chlorine isotope signatures in pore waters, as well as impregnation of sediments with petroleum and hydrocarbon potential. All seep sites have active gas seepage, near surface authigenic carbonates and gas hydrates. Cokheti Seep, Iberia Mound, and Pechori Mound are characterized by oil-stained sediments and gas seepage decoupled from deep fluid advection and bottom water intrusion induced by gas bubble release. Pechori Mound is further characterized by deep fluid advection of lower salinity pore fluids. The Pechori Mound pore fluids are altered by mineral/water reactions at elevated temperatures (between 60 and 110 °C) indicated by heavier oxygen and lighter chlorine isotope values, distinct Li and B enrichment, and K depletion. Strontium isotope ratios indicate that fluids originate from late Oligocene strata. This finding is supported by the occurrence of hydrocarbon impregnations within the sediments. Furthermore, light hydrocarbons and high molecular weight impregnates indicate a predominant thermogenic origin for the gas and oil at Pechori Mound, Iberia Mound, and Colkheti Seep. C₁₅₊ hydrocarbons at the oil seeps are allochtonous, whereas those at the Batumi seep area are autochthonous. The presence of oleanane, an angiosperm biomarker, suggests that the hydrocarbon source rocks belong to the Maikopian Formation. In summary, all investigated seep sites show a high hydrocarbon potential and hydrocarbons of Iberia Mound, Colkheti Seep, and Pechori Mound are predominantly of thermogenic origin. However, only at the latter seep site advection of deep pore fluids is indicated.  相似文献   

Experimental Study of the Brittle Behavior of Clay shale in Rapid Unconfined Compression   总被引：6，自引：3，他引：3  

Florian Amann  Edward Alan Button  Keith Frederick Evans  Valentin Samuel Gischig  Manfred Blümel 《Rock Mechanics and Rock Engineering》2011,44(4):415-430

The mechanical behavior of clay shales is of great interest in many branches of geo-engineering, including nuclear waste disposal, underground excavations, and deep well drilling. Observations from test galleries (Mont Terri, Switzerland and Bure, France) in these materials have shown that the rock mass response near the excavation is associated with brittle failure processes combined with bedding parallel shearing. To investigate the brittle failure characteristics of the Opalinus Clay recovered from the Mont Terri Underground Research Laboratory, a series of 19 unconfined uniaxial compression tests were performed utilizing servo-controlled testing procedures. All specimens were tested at their natural water content with loading approximately normal to the bedding. Acoustic emission (AE) measurements were utilized to help quantify stress levels associated with crack initiation and propagation. The unconfined compression strength of the tested specimens averaged 6.9 MPa. The crack initiation threshold occurred at approximately 30% of the rupture stress based on analyzing both the acoustic emission measurements and the stress–strain behavior. The crack damage threshold showed large variability and occurred at approximately 70% of the rupture stress.  相似文献   

Climate change effects on snow melt and discharge of a partly glacierized watershed in Central Switzerland (SoilTrec Critical Zone Observatory)     

Florian Kobierska  Tobias Jonas  Jan Magnusson  Massimiliano Zappa  Mathias Bavay  Thomas Bosshard  Frank Paul  Stefano M. Bernasconi 《Applied Geochemistry》2011

A comprehensive hydrological modeling study in the drainage area of a hydropower reservoir in central Switzerland is presented. Two models were tested to reproduce the measured discharge dynamics: (1) a detailed energy-balance model (ALPINE3D) primarily designed for snow simulations; (2) a conceptual runoff model system (PREVAH), including a distributed temperature-index snow and ice melt model. Considerable effort was put into distributing available meteorological station data to the model grids as forcing data. The recent EU regional climate modeling initiative ENSEMBLES provided up-to-date climate predictions for two 30-a periods in mid and late 21st century. These were used to estimate evolutions in the water supply of the hydropower reservoir in response to expected climate changes. The simulations suggest a shift of spring peak-flow by almost two months for the end of the century. Warmer winter temperatures will cause higher winter base-flow. Due to glacier retreat, late-summer flow will decrease at the end of the century.  相似文献   

Calcium isotope record of Phanerozoic oceans: Implications for chemical evolution of seawater and its causative mechanisms   总被引：1，自引：0，他引：1  

Juraj Farkaš  Florian Böhm  John Blenkinsop  Robert van Geldern  Silke Voigt 《Geochimica et cosmochimica acta》2007,71(21):5117-5134

A total of 280 brachiopods of Ordovician to Cretaceous age, complemented by published data from belemnites and planktonic foraminifera, are used to reconstruct the evolution of calcium isotope composition of seawater (δ^44/40Ca_SW) over the Phanerozoic. The compiled δ^44/40Ca_SW record shows a general increase from ∼1.3‰ (NIST SRM 915a) at the beginning of the Ordovician to ∼2‰ at present. Superimposed on this trend is a major long-term positive excursion from the Early Carboniferous to Early Permian as well as several short-term, mostly negative, oscillations.A numerical model of the global cycles of calcium, carbon, magnesium and strontium was used to estimate whether the recorded δ^44/40Ca_SW variations can be explained by varying magnitudes of input and output fluxes of calcium to the oceans. The model uses the record of marine ⁸⁷Sr/⁸⁶Sr ratios as proxy for seafloor spreading rates, a record of oceanic Mg/Ca ratios to estimate rates of dolomite formation, and reconstructed atmospheric CO₂, discharge and erosion rates to estimate continental weathering fluxes.The model results indicate that varying magnitudes of the calcium input and output fluxes cannot explain the observed δ^44/40Ca_SW trends, suggesting that the isotope signatures of these fluxes must also have changed. As a possible mechanism we suggest variable isotope fractionation in the sedimentary output flux controlled by the dominant mineralogy in marine carbonate deposits, i.e. the oscillating ‘calcite-aragonite seas’. The ultimate control of the calcium isotope budget of the Phanerozoic oceans appears to have been tectonic processes, specifically variable rates of oceanic crust production that modulated the hydrothermal calcium flux and the oceanic Mg/Ca ratio, which in turn controlled the dominant mineralogy of marine carbonates, hence the δ^44/40Ca_SW. As to the causes of the short-term oscillations recorded in the secular δ^44/40Ca_SW trend, we tentatively propose that these are related to variable rates of dolomite formation and/or to changing chemical composition of the riverine flux, in particular and ratios, induced by variable proportions of silicate vs. carbonate weathering rates on the continents.  相似文献