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101.
Martina Capponi Ahmed H. Mansi Daniele Sampietro 《Studia Geophysica et Geodaetica》2018,62(2):206-222
The precise computation of the vertical gravitational attraction of the topographic masses (terrain correction) is still being studied both for geodetic and geophysical applications. In fact, it is essential in high precision geoid estimation by means of the well-known remove-compute-restore technique, which is used to isolate the gravitational effects of anomalous masses in exploration geophysics. The terrain correction can be evaluated exploiting a Digital Terrain Model (DTM) in different ways, such as classical numerical integration, prisms, tesseroids, polyhedrons, and/or Fast Fourier Transform techniques. The increasing resolution of recently developed DTMs, the increasing number of observation points, and the increasing accuracy of gravity data represent, nowadays, major challenges for the terrain correction computation. Classical point mass approximation and prism based-algorithms are indeed too slow, while Fourier-based algorithms are usually too much approximate when compared to the required accuracy. In this work, we improve the Gravity Terrain Effects (GTE) algorithm, the innovative tool that exploits a combined prism-Fast Fourier Transform approach especially developed for airborne gravimetry, to compute the terrain correction on the surface of the DTM (i.e. corresponding to the ground stations and/or its vicinity). This required development of a proper adjustment of the algorithms implemented within the GTE software and also to define and implement a procedure to overcome the problems of the computation of the gravitational effects due to the actual slope of the terrain close to the stations. The latter problem is thoroughly discussed and solved by testing different solutions like concentric cylindrical rings, triangulated polyhedrons, or ultra-high resolution squared prisms. Finally, numerical tests to prove the temporal efficiency and the computational performances of the improved GTE software to compute terrain correction for ground stations are also presented. 相似文献
102.
Marc F. P. Bierkens Victoria A. Bell Peter Burek Nathaniel Chaney Laura E. Condon Cédric H. David Ad de Roo Petra Döll Niels Drost James S. Famiglietti Martina Flörke David J. Gochis Paul Houser Rolf Hut Jessica Keune Stefan Kollet Reed M. Maxwell John T. Reager Luis Samaniego Edward Sudicky Edwin H. Sutanudjaja Nick van de Giesen Hessel Winsemius Eric F. Wood 《水文研究》2015,29(2):310-320
103.
Daniel Karthe Sergey Chalov Vsevolod Moreido Margarita Pashkina Anna Romanchenko Gunsmaa Batbayar Andrei Kalugin Katja Westphal Marcus Malsy Martina Flörke 《Water Resources》2017,44(3):399-416
The Selenga River is the main artery feeding Lake Baikal. It has a catchment of ~450000 km² in the boundary region between Northern Mongolia and Southern Siberia. Climate, land use and dynamic socioeconomic changes go along with rising water abstractions and contaminant loads originating from mining sites and urban wastewater. In the future, these pressures might have negative impacts on the ecosystems of Lake Baikal and the Selenga River Delta, which is an important wetland region in itself and forms the last geobiochemical barrier before the Selenga drains into Lake Baikal. The following study aims to assess current trends in hydrology and water quality in the Selenga-Baikal basin, identify their drivers and to set up models (WaterGAP3 framework and ECOMAG) for the prediction of future changes. Of particular relevance for hydrological and water quality changes in the recent past were climate and land use trends as well as contaminant influx from mining areas and urban settlements. In the near future, additional hydrological modifications due to the construction of dams and abstractions/water diversions from the Selenga’s Mongolian tributaries could lead to additional alterations. 相似文献
104.
A primal C0-conforming virtual element discretization for the approximation of the bidimensional two-phase flow of immiscible fluids in porous media using general polygonal meshes is discussed. This work investigates the potentialities of the Virtual Element Method (VEM) in solving this specific problem of immiscible fluids in porous media involving a time-dependent coupled system of non-linear partial differential equations. The performance of the fully discrete scheme is thoroughly analysed testing it on general meshes considering both a regular problem and more realistic benchmark problems that are of interest for physical and engineering applications.
相似文献105.
Natural Hazards - The return period is a probabilistic criterion used to measure and communicate the random occurrence of geophysical events such as floods in risk assessment studies. Since an... 相似文献
106.
Martina K. Linnenluecke Alexander Stathakis Andrew Griffiths 《Global Environmental Change》2011,21(1):123-133
Growing scientific evidence suggests that human-induced climate change will bring about large-scale environmental changes such as sea-level rise and coastal flooding, extreme weather events and agricultural disruptions. The speed and extent of these changes and the expected impacts on social and corresponding economic and industrial systems are now moving to the forefront of debates. In this paper, we argue that climate change will lead to significant disruptions to firms which might ultimately create the necessity of a geographical shift of firm and industrial activities away from regions highly affected by climate change. Such a shift might become necessary due to (1) direct disruptions through climate change impacts on firm operations, for instance through droughts, floods, or sea level rise, and due to (2) disruptions in a firm's supplier, buyer or resource base that lead to flow-on effects and adverse consequences for a firm. We propose a framework for integrating firm relocation decisions into firm adaptive responses to climate change. The framework consists of three assessment steps: the level of risk from climate change impacts at a firm's location, the feasibility of relocation, and associated costs and benefits. We apply the framework to two case examples. The first case of electricity distribution firms in Victoria/Australia illustrates how the relocation (undergrounding) of cables could decrease the vulnerability of distribution networks to bushfires and the risk of electricity-caused fires, but would require significant investments. The second case of firms in the Australian pastoral industry points to geographic diversification of pastoral land holdings as possible adaptation option, but also to constraints in form of availability of suitable properties, ties to local communities, and adverse impacts on biodiversity. Implications for adaptation research and practice are outlined. 相似文献
107.
In the northern extension of the Famatina and the southern Puna (NW Argentina) prominent rhyolitic volcanic rocks traditionally referred to as Ordovician are exposed, resting on metamorphic basement and covered by thick Late Paleozoic siliciclastic successions. We report new U–Pb SHRIMP ages from these rhyolites that show them to be of Mississippian (348–342 Ma) age, thus identifying a previously unknown volcanic event in this portion of western Gondwana. Whole-rock geochemistry and Sr–Nd isotopic analyses suggest a crustal source for these rocks but with a juvenile input (εNd(t) between ? 2.91 and ? 0.3, and TDM values between 1.09 and 1.1 Ga). This is different from the Early Paleozoic magmatism of western Argentina where crustal recycling took place without any involvement of mantle material. The Carboniferous magmatism is compatible with an extensional environment developed along the Terra Australis accretionary orogen as a result of tectonic switching processes. These rhyolites may be related to the coeval Mississippian A-type granites exposed to the east, in the Sierras Pampeanas, confirming the regional character of this magmatism. 相似文献
108.
Maren Mohler Johannes Bühl Stephen Doherty Siegfried Eggl Vera Theresa Eybl François Farago Aleksandar Jaćimović Lars Hunger Nynne L. B. Lauritsen David Ludena Martina Meisnar Alexander Reissner Nicolas Sarda Benjamin Toullec Meritxell Viñas Tió 《Experimental Astronomy》2010,28(2-3):101-135
A high level of diversity has already been observed among the planets of our own Solar System. As such, one expects extrasolar planets to present a wide range of distinctive features, therefore the characterisation of Earth- and super Earth-like planets is becoming of key importance in scientific research. The Search (Spectropolarimetric Exoplanet AtmospheRe CHaracerisation) mission proposal of this paper represents one possible approach to realising these objectives. The mission goals of Search include the detailed characterisation of a wide variety of exoplanets, ranging from terrestrial planets to gas giants. More specifically, Search will determine atmospheric properties such as cloud coverage, surface pressure and atmospheric composition, and may also be capable of identifying basic surface features. To resolve a planet with a semi major axis of down to 1.4 AU and 30 pc distant Search will have a mirror system consisting of two segments, with elliptical rim, cut out of a parabolic mirror. This will yield an effective diameter of 9 m along one axis. A phase mask coronagraph along with an integral spectrograph will be used to overcome the contrast ratio of star to planet light. Such a mission would provide invaluable data on the diversity present in extrasolar planetary systems and much more could be learned from the similarities and differences compared to our own Solar System. This would allow our theories of planetary formation, atmospheric accretion and evolution to be tested, and our understanding of regions such as the outer limit of the Habitable Zone to be further improved. 相似文献
109.
The Wadden Sea (North Sea, Europe) is a shallow coastal sea with high benthic and pelagic primary production rates. To date, no studies have been carried out in the Wadden Sea that were specifically designed to study the relation between pelagic respiration and production by comparable methods. Because previous studies have suggested that the import of primary-produced pelagic organic matter is important for benthic Wadden Sea carbon budgets, we hypothesised that on an annual average the northern Wadden Sea water column is autotrophic. To test this hypothesis, we studied annual dynamics of primary production and respiration at a pelagic station in a shallow tidal basin (List Tidal Basin, northern Wadden Sea). Since water depth strongly influences production estimates, we calculated primary production rates per unit area in two ways: on the basis of the mean water depth (2.7 m) and on the basis of 1 m depth intervals and their respective spatial extent in the List Tidal Basin. The latter more precise estimate yielded an annual primary production of 146 g C m− 2 y− 1. Estimates based on the mean water depth resulted in a 40% higher annual rate of 204 g C m− 2 y− 1. The total annual pelagic respiration was 50 g C m− 2 y− 1. The P/R ratio varied between seasons: from February to October the water column was autotrophic, with the highest P/R ratio of 4–5 during the diatom spring bloom in April/May. In autumn and winter the water column was heterotrophic. On an annual average, the water column of the List Tidal Basin was autotrophic (P/R 3). We suggest that a large fraction of the pelagic produced organic matter was respired locally in the sediment. 相似文献
110.
Lukáš Ackerman Martina Krňanská Wolfgang Siebel Ladislav Strnad 《Mineralogy and Petrology》2010,99(3-4):185-199
In western Bohemia, the Drahotín (gabbro-diorite) and Mutěnín (gabbronorite-diorite-syenite) intrusions show different origins and patterns of geochemical evolution. Parental magmas of the Drahotín intrusion were derived predominantly from enriched mantle sources, and the melts have undergone a significant degree of assimilation-fractional crystallization (AFC) during their ascent and/or emplacement into the crust. In contrast, the compositional variation of the complex Mutěnín intrusion cannot be explained by simple AFC processes, but more likely reflects the involvement of several parental magmas. The gabbronorite was derived from a depleted mantle source, whereas the diorite/syenite stem from a mixed mantle-crust reservoir. The contrasting evolution of the Drahotín and Mutěnín intrusions may be due to their melt derivation and magma emplacement under different tectonothermal regimes at different times. 相似文献