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961.
Qin-Bo Cheng Christian Reinhardt-Imjela Xi Chen Achim Schulte Xiang Ji Fu-Lin Li 《水文科学杂志》2013,58(8):1460-1476
ABSTRACTA new physics-based rainfall–runoff method of the Soil and Water Assessment Tool (SWAT) was developed, which integrates a water balance (WB) approach with the variable source area (WB-VSA). This approach was further compared with four methods—soil-water-dependent curve number (CN-Soil), evaporation-dependent curve number (CN-ET), Green and Ampt equation (G&A) and WB—in a monsoonal watershed, Eastern China. The regional sensitivity analysis shows that volumetric efficiency coefficient (VE) with river discharges is sensitive to the most parameters of all approaches. The results of model calibration against VE demonstrate that WB-VSA is the most accurate owing to its reflection of the spatial variation of runoff generation as affected by topography and soil properties. Other methods can also mimic baseflow well, but the G&A and CN-ET simulate floods much worse than the saturation excess runoff approaches (WB-VSA, WB and CN-Soil). Meanwhile, CN-Soil as an empirical method fails to simulate groundwater levels. By contrast, WB-VSA captures them best.
Editor M.C. Acreman; Associate editor S. Kanae 相似文献
962.
Abstract The solution of the full nonlinear hydromagnetic dynamo problem is a major numerical undertaking. While efforts continue, supplementary studies into various aspects of the dynamo process can greatly improve our understanding of the mechanisms involved. In the present study, the linear stability of an electrically conducting fluid in a rigid, electrically insulating spherical container in the presence of a toroidal magnetic field Bo(r,θ)lø and toroidal velocity field Uo(r,θ)lø, [where (r,θ,ø) are polar coordinates] is investigated. The system, a model for the Earth's fluid core, is rapidly rotating, the magnetostrophic approximation is used and thermal effects are excluded. Earlier studies have adopted a cylindrical geometry in order to simplify the numerical analysis. Although the cylindrical geometry retains the fundamental physics, a spherical geometry is a more appropriate model for the Earth. Here, we use the results which have been found for cylindrical systems as guidelines for the more realistic spherical case. This is achieved by restricting attention to basic states depending only on the distance from the rotation axis and by concentrating on the field gradient instability. We then find that our calculations for the sphere are in very good qualitative agreement both with a local analysis and with the predictions from the results of the cylindrical geometry. We have thus established the existence of field gradient modes in a realistic (spherical) model and found a sound basis for the study of various other, more complicated, classes of magnetically driven instabilities which will be comprehensively investigated in future work. 相似文献
963.
Christian D. Klose 《Journal of Seismology》2013,17(1):109-135
A global catalog of small- to large-sized earthquakes was systematically analyzed to identify causality and correlatives between human-made mass shifts in the upper Earth??s crust and the occurrence of earthquakes. The mass shifts, ranging between 1?kt and 1?Tt, result from large-scale geoengineering operations, including mining, water reservoirs, hydrocarbon production, fluid injection/extractions, deep geothermal energy production and coastal management. This article shows evidence that geomechanical relationships exist with statistical significance between (a) seismic moment magnitudes M of observed earthquakes, (b) lateral distances of the earthquake hypocenters to the geoengineering ??operation points?? and (c) mass removals or accumulations on the Earth??s crust. Statistical findings depend on uncertainties, in particular, of source parameter estimations of seismic events before instrumental recoding. Statistical observations, however, indicate that every second, seismic event tends to occur after a decade. The chance of an earthquake to nucleate after 2 or 20?years near an area with a significant mass shift is 25 or 75?%, respectively. Moreover, causative effects of seismic activities highly depend on the tectonic stress regime in which the operations take place (i.e., extensive, transverse or compressive). Results are summarized as follows: First, seismic moment magnitudes increase the more mass is locally shifted on the Earth??s crust. Second, seismic moment magnitudes increase the larger the area in the crust is geomechanically polluted. Third, reverse faults tend to be more trigger-sensitive than normal faults due to a stronger alteration of the minimum vertical principal stress component. Pure strike-slip faults seem to rupture randomly and independently from the magnitude of the mass changes. Finally, mainly due to high estimation uncertainties of source parameters and, in particular, of shallow seismic events (<10?km), it remains still very difficult to discriminate between induced and triggered earthquakes with respect to the data catalog of this study. However, first analyses indicate that small- to medium-sized earthquakes (<M6) seem to be induced and large-sized events (>M6) seem to be triggered. The rupture propagation of triggered events might be dominated by pre-existing tectonic stress conditions. 相似文献
964.
The European Water Framework Directive (WFD) commits European Union member states to achieving good ecological status in all water bodies by 2015. For sediments the definition of good chemical status is based on numerical sediment quality guidelines. The aqua regia fraction is thus used for the evaluation of heavy metal concentrations in sediments. The chemical constituents in sediments responsible for mobility and toxicity are not considered generally. This article presents the combining of the sequential BCR procedure, for determining the chemical species of relevant elements, with the geoaccumulation index principle a numerical classification method for sediment quality guidelines. Using the BCR method it can be demonstrated that changes in element speciation can lead to more highly mobile species of trace elements which may affect the hazardous potential of sediments despite the “good chemical status” classification for aqua regia digestions. The Klinke stream is an urban surface water body located in Magdeburg, the state capital of Saxony‐Anhalt, Germany. Using this stream as an example it is shown that this additional information helps to describe the dynamics and discharge of the trace elements Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, Pd, Cd, Sb, Ba, Pb, Bi, and U into the Elbe River from urban water bodies. 相似文献
965.
Climatological drivers of changes in flood hazard in Germany 总被引:1,自引:0,他引:1
Fred F. Hattermann Zbigniew W. Kundzewicz Shaochun Huang Tobias Vetter Friedrich-Wilhelm Gerstengarbe Peter Werner 《Acta Geophysica》2013,61(2):463-477
Since several destructive floods have occurred in Germany in the last decades, it is of considerable interest and relevance (e.g., when undertaking flood defense design) to take a closer look at the climatic factors driving the changes in flood hazard in Germany. Even if there also exist non-climatic factors controlling the flood hazard, the present paper demonstrates that climate change is one main driver responsible for the increasing number of floods. Increasing trends in temperature have been found to be ubiquitous in Germany, with impact on air humidity and changes in (intense) precipitation. Growing trends in flood prone circulation pattern and heavy precipitation are significant in many regions of Germany over a multi-decade interval and this can be translated into the rise of flood hazard and flood risk. 相似文献
966.
Jordi Catalan Sergi Pla-Rabés Alexander P. Wolfe John P. Smol Kathleen M. Rühland N. John Anderson Jiři Kopáček Evžen Stuchlík Roland Schmidt Karin A. Koinig Lluís Camarero Roger J. Flower Oliver Heiri Christian Kamenik Atte Korhola Peter R. Leavitt Roland Psenner Ingemar Renberg 《Journal of Paleolimnology》2013,49(3):513-535
Over recent decades, palaeolimnological records from remote sites have provided convincing evidence for the onset and development of several facets of global environmental change. Remote lakes, defined here as those occurring in high latitude or high altitude regions, have the advantage of not being overprinted by local anthropogenic processes. As such, many of these sites record broad-scale environmental changes, frequently driven by regime shifts in the Earth system. Here, we review a selection of studies from North America and Europe and discuss their broader implications. The history of investigation has evolved synchronously with the scope and awareness of environmental problems. An initial focus on acid deposition switched to metal and other types of pollutants, then climate change and eventually to atmospheric deposition-fertilising effects. However, none of these topics is independent of the other, and all of them affect ecosystem function and biodiversity in profound ways. Currently, remote lake palaeolimnology is developing unique datasets for each region investigated that benchmark current trends with respect to past, purely natural variability in lake systems. Fostering conceptual and methodological bridges with other environmental disciplines will upturn contribution of remote lake palaeolimnology in solving existing and emerging questions in global change science and planetary stewardship. 相似文献
967.
Werner Kuhn 《International journal of geographical information science》2013,27(7):613-631
A method is proposed to derive ontologies of geographical domains from natural language texts that describe human activities. Through its textual grounding, the method addresses the issue of where to take the contents of ontologies from. Through its focus on actions afforded by domain objects, it establishes a criterion for selecting the contents. The actions are organized into a hierarchical theory of human activities in the domain. Using an analysis of the German traffic code as a case study, the paper demonstrates the informal parts of the process to derive such ontologies. 相似文献
968.
Sofus Christiansen Henrik S. Jensen Christian Wichmann Matthiessen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):117-123
Erland Porsmose: De fynske landsbyers historie: i dyrkningsfællesskabets tid. Odense University studies in history and social sciences, Vol. 109. 相似文献
969.
Marjorie L. Brooks Erica Fleishman Larry R. Brown Peggy W. Lehman Inge Werner Nathaniel Scholz Carys Mitchelmore James R. Lovvorn Michael L. Johnson Daniel Schlenk Suzanne van Drunick James I. Drever David M. Stoms Alex E. Parker Richard Dugdale 《Estuaries and Coasts》2012,35(2):603-621
Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors. 相似文献
970.
Changling He Jesper Bartholdy Christian Christiansen 《Environmental Earth Sciences》2012,67(3):759-769
To understand the behavior of trace metals in the salt marsh at Skallingen, Danish Wadden Sea, we investigated a profile from surface to 25?cm depth of the salt marsh sediment, focusing primarily on clay mineralogy and grain size distribution of the sediments and their relationship with trace metals. The clay assembly of the sediment consists of illite, kaolinite and much less chlorite and smectite. The major clay minerals of illite, kaolinite as well as chlorite correlate very poorly with all the trace metals investigated, due probably to the weak competing strength of these clays compared with the other adsorbents and to low availability of the mobile trace metals in the system. Correlation between trace metals and clay minerals may therefore be used as an indicator in environmental assessment. Fine grain fractions of the sediment increased markedly after salt marsh invasion in about 1931 but decreased after 1964. This increase was contributed mainly by the grains finer than 20???m while the fraction of 40?C63???m actually decreased soon after the invasion. The relation between most of the trace metals and grain size distributions is close in general but far from linear. The drastic turning point is observed at about 30???m, around where the correlation coefficient r drops from 0.8 to 0.1. Adsorption is the controlling mechanism for the behavior of trace metals in the salt marsh. Fe/Mn (hydr)oxides and organic matter play the key role. 相似文献