The magnetotelluric phase over 2-D structures     

Gaston Fischer  L. Szarka  A. Adam  J. T. Weaver 《Geophysical Journal International》1992,108(3):778-786

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An economic analysis of potential impacts of climate change in Egypt     

S Chib Onyeji  Günther Fischer 《Global Environmental Change》1994,4(4)

Projections of climate impacts on crop yields simulated for different General Circulation Model (GCM) scenarios are used, in a recursively dynamic general equilibrium framework, to account for potential economy-wide impacts of climate change in Egypt. Comparing these impact projections to those obtained under a reference, business-as-usual, scenario assuming some moderate changes in the political, economic or technological spheres, indicates that global warming has potentially negative effects. The analysis is based on a global assessment of potential climate change-induced variations in world commodity production and trade. The Egyptian agricultural sector, and the non-agricultural sector to a lesser extent, are projected to be increasingly less self-sufficient. Specific potential adverse impacts are identified. The simulation results show that high-cost adaptation measures involving major changes in the agricultural system and practices may mitigate these adverse impacts. Stimulating economic development of the rural areas and creating appropriate conditions for effective diffusion and development of technologies — particularly for the agricultural sector — would seem a desirable strategy. Perhaps, more importantly, the simulation results show that the assumption of exogenously determined technological progress may be inappropriate, in which case the potential adverse impacts of a future warming of the global climate are likely to be fewer than is indicated in this study — if prevailing constraints on productivity growth in the major food and feed grains are ‘released’ by endogenous advances in technology.  相似文献   

Aircraft measurements of sea surface conditions and their relationship to marine boundary-layer dynamics     

Aimé Druilhet  Pierre Durand  Alberte Fischer  Frédérique Said 《Boundary-Layer Meteorology》1990,52(4):397-414

Through simultaneous measurements, it is possible to demonstrate the relation between sea swell and surface temperature as measured by a thermoradiometer onboard an aircraft. Thermodynamic measurements made on board the aircraft enable analysis of the interaction between swell and surface marine layer dynamics. The cospectral functions of vertical turbulent transfer for sensible and latent heat indicate large-scale dynamic structures which would seem to be initiated by inhomogeneities in the humidity field. A cross-spectral examination of temperature and humidity produces a structure that is common to both parameters and is caused by swell propagation. The data used here were collected during the TOSCANE-T experiment, whose aim was to validate remote sensing scatterometer techniques, by means of an instrumented aircraft designed for atmospheric research.  相似文献   

Verknüpfung von Wasserbeschaffenheit und Wassermenge für das Grundwasser des Festgesteinsbereiches     

M. Schultze  H. Fischer  B. Gabriel 《洁净——土壤、空气、水》1990,18(6):673-681

Patterns of the typical groundwater quality for 13 hydrogeological units (lithofacies units) of the solid rock and for 5 stages of the contamination of groundwater by the agricultural production are derived from investigations carried out in six regions serving as examples and in evaluation of data series covering many years. The concentration values of the substances contained in water constituting the lower and upper limits of the typical width of variation are regarded as the quality of the groundwater reservoir (long retention time) and a fast runoff component of groundwater. On the basis of this model conception it is possible to determine one of the following four quantities from the other three quantities: groundwater quality, size of the groundwater reservoir, groundwater runoff with the shares of the slow component and of the fast one, removal of substances out of the root zone.  相似文献   

Reactivity of sandstone and siltstone samples from the Ketzin pilot CO2 storage site-Laboratory experiments and reactive geochemical modeling     

Sebastian Fischer  Axel Liebscher  Marco De Lucia  Lutz Hecht 《Environmental Earth Sciences》2013,70(8):3687-3708

To evaluate mineralogical-geochemical changes within the reservoir of the Ketzin pilot CO₂ storage site in Brandenburg, Germany, two sets of laboratory experiments on sandstone and siltstone samples from the Stuttgart Formation have been performed. Samples were exposed to synthetic brine and pure CO₂ at experimental conditions and run durations of 5.5 MPa/40 °C/40 months for sandstone and 7.5 MPa/40 °C/6 months for siltstone samples, respectively. Mineralogical changes in both sets of experiments are generally minor making it difficult to differentiate natural variability of the whole rock samples from CO₂-induced alterations. Results of sandstone experiments suggest dissolution of the anorthite component of plagioclase, anhydrite, K-feldspar, analcime, hematite and chlorite + biotite. Dissolution of the anorthite component of plagioclase, anhydrite and K-feldspars is also observed in siltstone experiments. In an inverse modeling approach, an extensive set of equilibrium simulations was set up in order to reproduce the experimental observations of the sandstone experiments. Simulations generally show fairly good matches with the experimental observations. Best matches with measured brine data are obtained from mineral combinations of albite, analcime, anhydrite, dolomite, hematite, illite, and kaolinite. The major discrepancies during equilibrium modeling, however, are reactions involving Fe²⁺ and Al³⁺. The best matching subsets of the equilibrium models were finally run including kinetic rate laws. These simulations reveal that experimentally determined brine data was well matched, but reactions involving K⁺ and Fe²⁺ are not fully covered. The modeling results identified key primary minerals as well as key chemical processes, but also showed that the models are not capable of covering all possible contingencies.  相似文献   

Numerical analysis of the groundwater regime in the western Dead Sea escarpment, Israel + West Bank   总被引：2，自引：2，他引：0  

Agnes Gräbe  Tino Rödiger  Karsten Rink  Thomas Fischer  Feng Sun  Wenqing Wang  Christian Siebert  Olaf Kolditz 《Environmental Earth Sciences》2013,69(2):571-585

Water is scarce in the semi-arid to arid regions around the Dead Sea, where water supply mostly relies on restricted groundwater resources. Due to increasing population in this region, the regional aquifer system is exposed to additional stress. This results in the continuous decrease in water level of the adjacent Dead Sea. The interaction of an increasing demand for water due to population growth and the decrease of groundwater resources will intensify in the near future. Thus, the water supply situation could worsen significantly unless sustainable water resource management is conducted. In this study, we develop a regional groundwater flow model of the eastern and southern Judea Group Aquifer to investigate the groundwater regime in the western Dead Sea drainage basin of Israel and the West Bank. An extensive geological database was developed and consequently a high-resolution structural model was derived. This structural model was the basis for various groundwater flow scenarios. The objective was to capture the spatial heterogeneity of the aquifer system and to apply these results to the southern part of the study area, which has not been studied in detail until now. As a result we analyzed quantitatively the flow regime, the groundwater mass balance and the hydraulic characteristics (hydraulic conductivity and hydraulic head) of the cretaceous aquifer system and calibrated them with PEST. The calibrated groundwater flow model can be used for integrated groundwater water management purposes in the Dead Sea area, especially within the framework of the SUMAR-Project.  相似文献   

Accuracy of the master-event and double-difference locations: synthetic tests and application to seismicity in West Bohemia, Czech Republic     

Fateh Bouchaala  Václav Vavryčuk  Tomáš Fischer 《Journal of Seismology》2013,17(3):841-859

The relative locations of earthquake hypocentres determined with the master-event (ME) or the double-difference (DD) methods are more accurate and less dispersive compared to the absolute locations. In this paper, we conduct synthetic tests to assess the accuracy of the ME and DD location methods, to study the effects of the control parameters on the locations and possible distortions of the foci geometry. The results indicate that the DD locations are, in general, more accurate than the ME locations and perform significantly better for large earthquake clusters due to their independence of the master event position. The location precision, however, strongly depends on the control parameters used. If the control parameters are optimally chosen, the location errors can be considerably reduced. Moreover, it is proved that no distortion such as artificial clustering of foci is introduced if relative locations are used. Finally, the efficiency of both location methods is exemplified on locations of swarm micro-earthquakes that occurred in the West Bohemia region, Czech Republic, in order to reveal a detailed geometry of the active fault zone.  相似文献   

Breit–Pauli energy levels, transition probabilities and lifetimes for 3d⁵ levels in Fe iv of astrophysical interest     

Charlotte Froese Fischer  Robert H. Rubin 《Monthly notices of the Royal Astronomical Society》2004,355(2):461-474

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Sensing with boots and trousers — qualitative field observations of shallow soil moisture patterns     

Michael Rinderer  Andrea Kollegger  Benjamin M. C. Fischer  Manfred Stähli  Jan Seibert 《水文研究》2012,26(26):4112-4120

While soil moisture patterns can be interesting traits to investigate spatio‐temporal heterogeneity of catchments relevant for various physical processes of soil–atmosphere interaction and soil water redistribution, many of the existing methods to capture spatial patterns are time consuming, expensive or need site‐specific calibration. In this study we present a quick and inexpensive supplementary field method for classifying soil wetness in wet environments. The seven wetness classes are based on qualitative indicators, which one can touch, hear or see on the soil surface. To counter critics that such qualitative methods are considerably affected by subjectivity, we performed systematic testing of the method by taking qualitative measurements in the field with 20 non‐expert raters. We then analyzed these in terms of degree of agreement and assessed the results against gravimetric sampling and time domain reflectometry measurements. In 70% of all classifications raters agreed on the wetness class assigned to the marked sampling locations and in 95% they were not off by more than one wetness class. The seven quantitative wetness classes agreed with gravimetric and time domain reflectometry measurements, although intermediate to wet classes showed an overlap of their range whereas the driest classes showed considerable spread. Despite some potential to optimize the method, it has been shown to be a reliable supplement to existing quantitative techniques for assessing soil moisture patterns in wet environments. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A comparison of analytic and numerical results for a two-dimensional control model in electromagnetic induction – I. B-polarization calculations     

J. T. Weaver  B. V. Le Quang  G. Fischer 《Geophysical Journal International》1985,82(2):263-277

Summary. A conducting slab of finite thickness divided into three segments of different conductivities and overlying a perfect conductor is proposed as a suitable two-dimensional 'control' model for testing the accuracy of the various numerical modelling programs that are available for calculating the fields induced in the Earth by an external, time-varying magnetic source. An analytic solution is obtained for this control model for the case of the magnetic field everywhere parallel to the conductivity boundaries ( B -polarization). Values of the field given by this solution for a particular set of model parameters are calculated at selected points on the surface and on a horizontal plane inside the conductor, and are tabulated to three figure accuracy for reference. They are used to check the accuracy of the results given by the finite difference program of Brewitt-Taylor & Weaver and the finite element program of Kisak & Silvester for the same model. Improved formulae for calculating the derived electric field components in B -polarization are first developed for incorporation in the finite difference program, and these give surface electric fields within 1 per cent of the analytic values, while all three field components inside the conductor are calculated to better than 96 per cent accuracy by the finite difference program. The results given by the finite element program are not quite so satisfactory. Errors somewhat greater than 10 per cent are present and although the program requires much less disk space it takes rather more CPU time to complete the calculations.  相似文献