Multi‐method virtual electromagnetic experiments for developing suitable monitoring designs: A fictitious CO2 sequestration scenario in Northern Germany          下载免费PDF全文

Jana H. Börner  Feiyan Wang  Julia Weißflog  Matthias Bär  Ines Görz  Klaus Spitzer 《Geophysical Prospecting》2015,63(6):1430-1449

We present a numerical study for 3D time‐lapse electromagnetic monitoring of a fictitious CO₂ sequestration using the geometry of a real geological site and a suite of suitable electromagnetic methods with different source/receiver configurations and different sensitivity patterns. All available geological information is processed and directly implemented into the computational domain, which is discretized by unstructured tetrahedral grids. We thus demonstrate the performance capability of our numerical simulation techniques. The scenario considers a CO₂ injection in approximately 1100 m depth. The expected changes in conductivity were inferred from preceding laboratory measurements. A resistive anomaly is caused within the conductive brines of the undisturbed reservoir horizon. The resistive nature of the anomaly is enhanced by the CO₂ dissolution regime, which prevails in the high‐salinity environment. Due to the physicochemical properties of CO₂, the affected portion of the subsurface is laterally widespread but very thin. We combine controlled‐source electromagnetics, borehole transient electromagnetics, and the direct‐current resistivity method to perform a virtual experiment with the aim of scrutinizing a set of source/receiver configurations with respect to coverage, resolution, and detectability of the anomalous CO₂ plume prior to the field survey. Our simulation studies are carried out using the 3D codes developed in our working group. They are all based on linear and higher order Lagrange and Nédélec finite‐element formulations on unstructured grids, providing the necessary flexibility with respect to the complex real‐world geometry. We provide different strategies for addressing the accuracy of numerical simulations in the case of arbitrary structures. The presented computations demonstrate the expected great advantage of positioning transmitters or receivers close to the target. For direct‐current geoelectrics, 50% change in electric potential may be detected even at the Earth's surface. Monitoring with inductive methods is also promising. For a well‐positioned surface transmitter, more than 10% difference in the vertical electric field is predicted for a receiver located 200 m above the target. Our borehole transient electromagnetics results demonstrate that traditional transient electromagnetics with a vertical magnetic dipole source is not well suited for monitoring a thin horizontal resistive target. This is due to the mainly horizontal current system, which is induced by a vertical magnetic dipole.  相似文献   

Influence of the equatorial deep jets on the north equatorial countercurrent   总被引：1，自引：1，他引：0  

Jan-Dirk Matthießen  Richard J. Greatbatch  Peter Brandt  Martin Claus  Sven-Helge Didwischus 《Ocean Dynamics》2015,65(8):1095-1102

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Modelling forest snow processes with a new version of WaSiM     

Kristian Förster  Jakob Garvelmann  Gertraud Meißl  Ulrich Strasser 《水文科学杂志》2013,58(10):1540-1557

ABSTRACT

We present a new model extension for the Water balance Simulation Model, WaSiM, which features (i) snow interception and (ii) modified meteorological conditions under coniferous forest canopies, complementing recently developed model extensions for particular mountain hydrological processes. Two study areas in Austria and Germany are considered in this study. To supplement and constrain the modelling experiments with on-site observations, a network of terrestrial time-lapse cameras was set up in one of these catchments. The spatiotemporal patterns of snow depth inside the forest and at the adjacent open field sites were recorded along with snow interception dynamics. Comparison of observed and modelled snow cover and canopy interception indicates that the new version of WaSiM reliably reconstructs the variability of snow accumulation for both the forest and the open field. The Nash-Sutcliffe efficiency computed for selected runoff events in spring increases from ?0.68 to 0.71 and 0.21 to 0.87, respectively.  相似文献   

Floods in megacity environments: vulnerability and coping strategies of slum dwellers in Dhaka/Bangladesh     

Boris Braun  Tibor Aßheuer 《Natural Hazards》2011,58(2):771-787

In many megacities of the global south, the combination of rapid population growth and high pressure on space for housing, results in urban growth taking place in areas particularly prone to natural hazards. Dhaka, the capital of Bangladesh, is no exception to this rule. Many marginal settlements or slums are located on low-lying land at high risk of flooding. This paper analyzes the vulnerability of slum dwellers in Dhaka and highlights the major factors behind their sensitivity to floods and their ability to adapt to the related changes. The empirical findings presented are based on a questionnaire survey covering 625 households in five slum areas of Dhaka. Our data suggests that social capital plays an important role with regard to the ability of slum dwellers to find ways to live with the floods. Regardless of how strongly people are affected, mutual help and support are dominant features in times of crises. While poorly educated and resourced slum dwellers are highly vulnerable to external shocks, they still show a surprising capacity to cope with natural calamities.  相似文献   

Linear dichroism in ALD layers of TiO2     

C. Das  M. Tallarida  D. Schmeißer 《Environmental Earth Sciences》2013,70(8):3785-3795

We prepare TiO₂ film by ALD and study their electronic properties by soft X-ray absorption spectroscopy (XAS) and photoelectron spectroscopy. We focus on XAS and X-ray linear dichroism to indentify band onset and learn about local distortion of the Ti–O octahedral atomic and about defects which cause Ti-based electronic states within the band gap.  相似文献   

Ambient pressure thermal desorption spectroscopy (AP-TDS) of NiO/SiO2 catalysts     

M. Städter  K. Müller  F. Rachow  M. Richter  D. Schmeißer 《Environmental Earth Sciences》2013,70(8):3779-3784

The Sabatier reaction is a key process in the “power-to-gas” application which is considered to contribute to future chemical energy storage systems. In this contribution we focus on the catalytic active sites of a NiO catalyst supported on SiO₂ (NiO/SiO₂) which is commonly used in the Sabatier reaction. A novel technique for the characterization of the active sites is presented and discussed using thermal desorption spectroscopy at ambient pressure. This analytical tool is operated under reaction conditions and allows element specific measurements during the catalytic process of CO₂ reforming towards methane. Beside the desorption experiments, XPS and XAS measurements of pristine and catalytically used samples are performed to determine the influence of the Sabatier reaction conditions on the surface structure of the catalyst.  相似文献   

A new data set of satellite-derived surface albedo values for operational use at ECMWF     

J. F. Geleyn  H. J. Preuß 《Meteorology and Atmospheric Physics》1983,32(4):353-359

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Pi 2 pulsations and the eastward electrojet: A case study     

Mark Lester  Karl-Heinz Glaßmeier  Jörg Behrens 《Planetary and Space Science》1985,33(3):351-364

We report the results of a case study of two Pi 2 pulsations observed near the eastward electrojet by the Scandinavian Magnetometer Array. The power of the two Pi 2 pulsations, calculated using a standard Fast Fourier Transform method, peaks near the centre of the eastward electrojet. For both events there is a strong latitudinal gradient in the power poleward of the equatorward border of the electrojet. The sense of polarisation is predominantly clockwise at the northern stations and anticlockwise at the southern stations although the reversal from clockwise to anticlockwise does not occur at a constant latitude. For the first event the polarisation reversal occurs at higher latitudes in the western half of the array; for the second the polarisation reversal occurs at higher latitudes at the edges of the array. The polarisation reversal does not appear to be related to the location of the eastward electrojet. Equivalent current vectors of the Pi 2 pulsations, obtained by rotating the band pass filtered data through 90°, exhibit clear vortex structures in both events. The vortices change sense of direction at half the period of the Pi 2 pulsation. A simple model for the ionospheric electric field in accord with the field line resonance theory reconstructs the basic features of the observed Pi 2 equivalent current system. We thus conclude that Pi 2 signatures in the region of the eastward electrojet and far away from the auroral break-up region are governed by the field line resonance mechanism.  相似文献   

Co-ordinated traffic in a transponder based co-operative system. presentation of the NADAKOS- project     

Reinhard Müller  Thoralf Weißflog  Anke ZÖlder 《Ocean Dynamics》1997,49(4):499-510

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Die Bedeutung des elektromagnetischen Erdfeldes in der Bioklimatologie     

H. Loßnitzer 《Theoretical and Applied Climatology》1951,3(1):297-307

Zusammenfassung Viele meteorobiologische Untersuchungen lassen vermuten, daß kolloidelektrische Vorgänge im Übertragungsmechanismus zwischen Umwelt und Organismen eine bedeutsame Rolle spielen. Diese Hinweise werden diskutiert und insbesondere die geoelektrischen Faktoren besprochen, die hierin von Einfluß sein können; als Indikatoren erscheinen Erdströme besonders geeignet. An speziellen Erdstromregistrierungen werden eine Anzahl atmosphärischer Einflüsse nachgewiesen. Registrierungen von elektromagnetischen Feldstörungen können aber darüber hinaus auch für die allgemeine Meteorologie und die Wettervorhersage bedeutungsvoll sein.

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Summary A great number of meteorobiological investigations induce to suppose that colloido-electric processes are of great importance for the mechanism of transmission between environment and organism. These aspects are discussed and especially the geo-electric factors which therein may have a considerable influence, whereof earth-currents are especially qualified as indicators. Different atmospheric influences are showed by special records of earth-currents; beyond it, the records of electromagnetic field perturbations seem to be important for general meteorology and for weather-forecasting.

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Résumé De nombreuses recherches météorobiologiques conduisent à l'hypothèse que des processus colloido-électriques jouent un rôle important dans le mécanisme de translation entre milieu et organisme. Ces aspects sont discutéet et surtout les facteurs géoélectriques qui peuvent y avoir une influence; comme indicateurs les courants telluriques paraissent être au premier plan. Certaines influences atmosphériques sont démontrées par des enregistrements spéciaux de courant tellurique. Par-dessus cela, des enregistrements des perturbations du champs électromagnétique peuvent être de grande importance pour la météorologie générale et pour les prévisions du temps.

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Mit 4 Textabbildungen.  相似文献