Gravity reduction with three-dimensional atmospheric pressure data for precise ground gravity measurements     

Juergen Neumeyer  Jan Hagedoorn  Jens Leitloff  Torsten Schmidt 《Journal of Geodynamics》2004,38(3-5):437

The redistribution of air masses induces gravity variations (atmospheric pressure effect) up to about 20 μgal. These variations are disturbing signals in gravity records and they must be removed very carefully for detecting weak gravity signals. In the past, different methods have been developed for modelling of the atmospheric pressure effect. These methods use local or two-dimensional (2D) surface atmospheric pressure data and a standard height-dependent air density distribution. The atmospheric pressure effect is consisting of the elastic deformation and attraction term. The deformation term can be well modelled with 2D surface atmospheric pressure data, for instance with the Green's function method. For modelling of the attraction term, three-dimensional (3D) data are required. Results with 2D data are insufficient.From European Centre for Medium-Range Weather Forecasts (ECMWF) 3D atmospheric pressure data are now available. The ECMWF data used here are characterised by a spacing of Δ and Δλ = 0.5°, 60 pressure levels up to a height of 60 km and an interval of 6 h. These data are used for modelling of the atmospheric attraction term. Two attraction models have been developed based on the point mass attraction of air segments and the gravity potential of the air masses. The modelling shows a surface pressure-independent part of gravity variations induced by mass redistribution of the atmosphere in the order of some μgal. This part can only be determined by using 3D atmospheric pressure data. It has been calculated for the Vienna Superconducting Gravimeter site.From this follows that the gravity reduction can be improved by applying the 3D atmospheric attraction model for analysing long-periodic tidal waves including the polar tide. The same improvement is expected for reduction of long-term absolute gravity measurements or comparison of gravity measurements at different seasonal times. By using 3D atmospheric pressure data, the gravity correction can be improved up to some μgal.  相似文献   

Thermal infrared remote sensing of volcanic emissions using the moderate resolution imaging spectroradiometer   总被引：1，自引：0，他引：1  

I. M. Watson  V. J. Realmuto  W. I. Rose  A. J. Prata  G. J. S. Bluth  Y. Gu  C. E. Bader  T. Yu 《Journal of Volcanology and Geothermal Research》2004,135(1-2):75

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Troposphere–stratosphere response to large-scale North Atlantic Ocean variability in an atmosphere/ocean coupled model     

N.-E. Omrani  Jürgen Bader  N. S. Keenlyside  Elisa Manzini 《Climate Dynamics》2016,46(5-6):1397-1415

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Ukinrek Maars, Alaska, II. Deposits and formation of the 1977 craters     

Stephen Self  Juergen Kienle  Jean-Paul Huot   《Journal of Volcanology and Geothermal Research》1980,7(1-2)

The initial phase of the eruption forming Ukinrek Maars during March and April 1977 were explosions from the site of West Maar. These were mainly phreatomagmatic and initially transitional to strombolian. Activity at West Maar ceased after three days upon the initiation of the East Maar. The crater quickly grew by strong phreatomagmatic explosions. During the first phases of phreatomagmatic activity at East Maar, large exotic blocks derived from a subsurface till were ejected. Ballistic studies indicate muzzle velocities for these blocks of 80–90 m s⁻¹.Phreatomagmatic explosions ejected both juvenile and non-juvenile material which formed a low rim of ejecta (< 26 mhigh) around the crater and a localized, coarse, wellsorted (σ_φ = 1−1.5) juvenile and lithic fall deposit. Other fine ash beds, interstratified with the coarse beds, are more poorly sorted (σ_φ = 2−3) and are interpreted as fallout of wet, cohesive ash from probably milder phases of activity in the crater. Minor base surge activity damaged trees and deposited fine ash, including layers plastered on vertical surfaces. Viscous basalt lava appeared in the center of the East Maar crater almost immediately and a lava dome gradually grew in the crater despite phreatomagmatic eruptions adjacent to it.The development of these maars appears to be mainly controlled by gradual collapse of crater and conduit walls, and blasting-out of the slumped debris by phreatomagmatic explosions when rising magma contacted groundwater beneath the regional water table and a local perched aquifer.Ballistic analysis on the ejected blocks indicates a maximum muzzle velocity of 100–150 m s^-1, values similar to those obtained from other ballistic studies on maar ejecta.  相似文献   

Barriers in the science-policy-practice interface: Toward a knowledge-action-system in global environmental change research     

Juergen Weichselgartner  Roger Kasperson 《Global Environmental Change》2010,20(2):266-277

This paper presents the results of a case study analysis from the knowledge domains of vulnerability and resilience. We analyzed 20 scientific assessments to provide empirical evidence for successes and failures in collaborative knowledge production, i.e., the joint creation of assessments reports by researchers and decision makers in policy and practice. It became clear that the latter typically use insufficiently the research-based knowledge available and researchers typically produce insufficiently knowledge that is directly usable. We found a number of functional, structural, and social factors inhibiting a joint problem identification and framing of knowledge producers and potential users: divergent objectives, needs, scope, and priorities; different institutional settings and standards, as well as differing cultural values, understanding, and mistrust. Combining understanding from multiple sources and providing mechanisms for linking solutions proposed by research with articulated needs and problems of practitioners would reduce the discrepancies in activities of different actors and result in more timely and context-appropriate solutions. In the concluding section we argue for a more locally embedded and socially contingent production of actionable knowledge and make suggestions about ways to enhance effectiveness of research-based knowledge.  相似文献   

Evaluating along‐strike variation using thin‐bedded facies analysis,Upper Cretaceous Ferron Notom Delta,Utah          下载免费PDF全文

Zhiyang Li  Janok Bhattacharya  Juergen Schieber 《Sedimentology》2015,62(7):2060-2089

Thin‐bedded delta‐front and prodelta facies of the Upper Cretaceous Ferron Notom Delta Complex near Hanksville in southern Utah, USA, show significant along‐strike facies variability. Primary initiation processes that form these thin beds include surge‐type turbidity currents, hyperpycnal flows and storm surges. The relative proportion of sedimentary structures generated by each of these depositional processes/events has been calculated from a series of measured sedimentological sections within a single parasequence (PS6–1) which is exposed continuously along depositional strike. For each measured section, sedimentological data including grain size, lithology, bedding thickness, sedimentary structures and ichnological suites have been documented. Parasequence 6–1 shows a strong along‐strike variation with a wave‐dominated environment in the north, passing abruptly into a fluvial‐dominated area, then to an environment with varying degrees of fluvial and wave influence southward, and back to a wave‐dominated environment further to the south‐east. The lateral facies variations integrated with palaeocurrent data indicate that parasequence 6–1 is deposited as a storm‐dominated symmetrical delta with a large river‐dominated bayhead system linked to an updip fluvial feeder valley. This article indicates that it is practical to quantify the relative importance of depositional processes and determine the along‐strike variation within an ancient delta system using thin‐bedded facies analysis. The wide range of vertical stratification and grading sequences present in these event beds also allows construction of conceptual models of deposition from turbidity currents (i.e. surge‐type turbidity currents and hyperpycnal flows) and storm surges, and shows that there are significant interactions and linkages of these often paired processes.  相似文献   

High-P granulites of the Songshugou area (Qinling Orogen,east-central China): Petrography,phase relations,and U/Pb zircon geochronology     

Thomas Bader  Lifei Zhang  Xiaowei Li  Bin Xia  Leander Franz  Christian de Capitani  Qingyun Li 《Journal of Metamorphic Geology》2020,38(4):421-450

High-pressure (HP) granulites provide telling records of mineral reactions at upper mantle to lower crustal levels and key information on the fate of material in subduction systems. The latter especially applies when they abut eclogite and mantle dunite because such rock associations are crucial for understanding the incompletely known processes at the interface of converging plates. A continental arc, active c. 520–395 Ma ago, formed an enigmatic example of such a rock association in the Songshugou area, Qinling Orogen. To unravel the juxtaposition of the distinct rocks, this study combines petrography, phase equilibria modelling, conventional thermobarometry, and zircon U–Th–Pb–Ti–REE analysis. Two mafic HP granulites, which contain the mineral assemblages garnet–clinopyroxene–plagioclase–rutile–mesoperthite–quartz and garnet–clinopyroxene–plagioclase–rutile, experienced peak metamorphic conditions of ≤1.4 GPa, 860°C and ~1.3 GPa, ≥910°C, respectively. During decompression and cooling, at 489 ± 4 Ma, amphibole lamellae unmixed from a clinopyroxene solid solution and orthopyroxene in part replaced garnet. A felsic HP granulite shows equilibration of garnet, perthite, antiperthite, kyanite, quartz, and rutile at 810–860°C, ~1.2 GPa, sillimanite growth during decompression, and upper amphibolite facies cooling at 510 ± 4 Ma. Though the thermobarometric data are just within the methodological errors, the U/Pb zircon ages imply the HP granulites did not evolve coherently. The HP granulites either represent foundered lower arc crust or originated from subduction erosion because their geochemistry is indistinguishable from that of the hanging-wall plate. Published and new pressure–temperature–time–deformation paths converge at ~710°C, ~0.9 GPa, and ≲470 Ma, implying exhumation tectonics juxtaposed the HP granulites with a mélange of eclogite and mantle dunite at lower crustal levels. This study highlights that lower arc crust can comprise material of diverse evolution.  相似文献   

Encounters with an unearthly mudstone: Understanding the first mudstone found on Mars          下载免费PDF全文

Juergen Schieber  David Bish  Max Coleman  Mark Reed  Elisabeth M. Hausrath  John Cosgrove  Sanjeev Gupta  Michelle E. Minitti  Kenneth S. Edgett  Mike Malin 《Sedimentology》2017,64(2):311-358

The Sheepbed mudstone forms the base of the strata examined by the Curiosity rover in Gale Crater on Mars, and is the first bona fide mudstone known on another planet. From images and associated data, this contribution proposes a holistic interpretation of depositional regime, diagenesis and burial history. A lake basin probably received sediment pulses from alluvial fans. Bed cross‐sections show millimetre to centimetre‐scale layering due to distal pulses of fluvial sediment injections (fine‐grained hyperpycnites), fall‐out from river plumes, and some aeolian supply. Diagenetic features include mineralized synaeresis cracks and millimetre‐scale nodules, as well as stratiform cementation. Clay minerals were initially considered due to in situ alteration, but bulk rock chemistry and mineralogy suggests that sediments were derived from variably weathered source rocks that probably contained pre‐existing clay minerals. X‐ray diffraction analyses show contrasting clay mineralogy in closely spaced samples, consistent with at least partial detrital supply of clay minerals. A significant (ca 30 wt%) amorphous component is consistent with little post‐depositional alteration. Theoretical modelling of diagenetic reactions, as well as kinetic considerations, suggest that the bulk of diagenetic clay mineral formation occurred comparatively late in diagenesis. Diagenetic features (synaeresis cracks and nodules) were previously thought to reflect early diagenetic gas formation, but an alternative scenario of synaeresis crack formation via fabric collapse of flocculated clays appears more likely. The observed diagenetic features, such as solid nodules, hollow nodules, matrix cement and ‘raised ridges’ (synaeresis cracks) can be explained with progressive alteration of olivine/glass in conjunction with centrifugal and counter diffusion of reactive species. Anhydrite‐filled fractures in the Sheepbed mudstone occurred late in diagenesis when fluid pressures built up to exceed lithostatic pressure. Generating fluid overpressure by burial to facilitate hydraulic fracturing suggests a burial depth of at least 1000 m for the underlying strata that supplied these fluids.  相似文献   

Influence of age,size and condition factor on lipid concentration in the snapper Chrysophrys auratus     

Hamish Allen  Martin Bader  Tom Rowlands 《新西兰海洋与淡水研究杂志》2018,52(2):295-307

Survival, growth rates and functionality of larvae have been hypothesised to correlate with higher lipid provisioning in older teleosts. To test the lipid provisioning part of this hypothesis, we investigated the total and relative (mg/g) lipid (triglyceride) concentration in both the source (liver) and sink (gonad) lipidation organs of female snapper Chrysophrys auratus across age, size and condition factor throughout its spawning season. Age, size and condition factor had little discernible effect on the total or relative lipid concentration in either liver or gonadal tissue. Therefore, if oocyte quality (based on triglyceride concentration) is comparable across a population, research on the relationship between lipidomics and reproductive success needs to move beyond highlighting correlations to elucidating causation by focusing on the biochemical mechanisms of egg quality and larval survival, identifying maternal parameters associated with consistent lipid provisioning, and partitioning of phenotypic and genotypic maternal influences.  相似文献   

The use of single seeding events to evaluate the effect of hail suppression     

H. H. Schiesser  J. Bader  A. Waldvogel 《Theoretical and Applied Climatology》1992,46(2-3):123-133

Summary During the years 1977–82 a randomized hail suppression experiment, Grossversuch IV, was conducted in Central Switzerland, testing a Soviet seeding method, which was called the competing embryo concept. Due to logistical and technical difficulties there were several seeded hail cells with insufficient seeding coverage. This fact complicates a statistically proper evaluation of the experiment.To overcome the problem of insufficient seeding, a method is demonstrated, which takes a single seeding event (in our case one rocket) as the statistical unit instead of the seeded cell. The assumption is made that each rocket, which hit the zone of hail formation, reduces the hail production and can be investigated independently from the others. 19 seed cells with 226 truly fired rockets and 18 control cells with 170 simulated rockets, representing over 90% of the total global kinetic energy of all Grossversuch IV cells, were selected. A randomization test is introduced to test the average differences of the true and simulated seeding events. A highly significant increase of kinetic energy after seeding (p-value around 1%) is observed. This result supports the statistically non-significant trend obtained in the confirmatory analysis.With 4 Figures  相似文献