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151.
V. Rizi G. Redaelli G. Visconti F. Masci C. Wedekind B. Stein F. Immler B. Mielke P. Rairoux L. Woste M. Del Guasta M. Morandi F. Castagnoli S. Balestri L. Stefanutti R. Matthey V. Mitev M. Douard J.P. Wolf E. Kyro M. Rummukainen R. Kivi 《Journal of Atmospheric Chemistry》1999,32(1):165-181
Polar stratospheric clouds (PSC) were observed with the multi-wavelength lidar of the MOANA project (Modelling and Observations of Aerosols in the Northern Atmosphere) during SESAME (Second European Stratospheric Arctic and Mid-latitude Experiment). The physical state, liquid or solid, of the cloud particles can be inferred from the lidar data. Using isentropic back-trajectories to obtain the thermal history of the sampled air masses, it is possible to reconcile most of the observations with current ideas on PSC formation and evolution. When the cloud particles were identified as liquid, changes in the size distribution of the droplets along the trajectory were calculated using a micro-physical box model. Backscatter ratios calculated from the size distributions are in broad agreement with the lidar data, giving confidence in current understanding of the evolution of ternary solution (H2SO4, HNO3 and H2O) droplets.Results from two soundings are shown which bear on the problem of the formation of solid particles. In the first, solid particles were detected. The air mass had cooled to the frost point 12 hours earlier. In the second no solid particles were detected although the air temperature was below the nitric acid trihydrate existence point, and had decreased by 12K in the previous 14 hours. 相似文献
152.
The cave bear was a prominent member of the Upper Pleistocene fauna in Eurasia. While breakthroughs were recently achieved with respect to its phylogeny using ancient DNA techniques, it is still challenging to date cave bear fossils beyond the radiocarbon age range. Without an accurate and precise chronological framework, however, key questions regarding the palaeoecology cannot be addressed, such as the extent to which large climate swings during the last glacial affected the habitat and possibly even conditioned the final extinction of this mammal. Key to constraining the age of cave bear fossils older than the lower limit of radiocarbon dating is to date interlayered speleothems using 230Th/U. Here we report new results from one such site in the Eastern European Alps (Schwabenreith Cave), which yielded the highest density of bones of cave bear (Ursus spelaeus eremus). Although dating of the flowstones overlying this fossiliferous succession was partly compromised by diagenetic alteration, the 230Th/U dates indicate that the bear hibernated in this cave after about 113 ka and before about 109 ka. This time interval coincides with the equivalent of Greenland Stadial 25, suggesting possible climate control on the cave bear's habitat and behaviour. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd 相似文献
153.
Clar Christoph Löschner Lukas Nordbeck Ralf Fischer Tatjana Thaler Thomas 《Natural Hazards》2021,105(2):1765-1796
Natural Hazards - This contribution explores the conceptual and empirical linkages between population dynamics and natural hazard risk management (NHRM). Following a review of the international... 相似文献
154.
Christoph Lhotka 《Celestial Mechanics and Dynamical Astronomy》2009,104(1-2):175-189
Series expansions are widely used objects in perturbation theory in Celestial Mechanics and Physics in general. Their application nevertheless is limited due to the fact of convergence problems of the series on the one hand and constricted to regions in phase space, where small (expansion) parameters remain small on the other hand. In the mapping case, to overcome the latter problem, e.g., different expansion points are used to cover the whole phase space, resulting in a set of dynamical mappings for one dynamical system. In addition, the accuracy of such expansions depend not only on the order of truncation but also on the definition of the grid of the expansion points in phase space. A simple modification of the usual approach allows to increase the accuracy of the expanded mappings and to cover the whole phase space, where the series converge. Convergence problems due to the nonintegrability of the system can never be ruled out of the system, but the convergence of the series expansions in mapping models, which are convergent can be improved. The underlying idea is based on dynamic expansion points, which are the main subject of this article. As I will show it is possible to derive unique linear mappings, based on dynamically expanded generating functions, for the 3:1 resonance and the coupled standard map, which are valid in their whole phase spaces. 相似文献
155.
Christoph Zöckler Lera Miles Lucy Fish Annett Wolf Gareth Rees Fiona Danks 《Climatic change》2008,87(1-2):119-130
Climate change is expected to alter the distribution of habitats and thus the distribution of species connected with these
habitats in the terrestrial Barents Sea region. It was hypothesised that wild species connected with the tundra and open-land
biome may be particularly at risk as forest area expands. Fourteen species of birds were identified as useful indicators for
the biodiversity dependent upon this biome. By bringing together species distribution information with the LPJ-GUESS vegetation
model, and with estimates of future wild and domestic reindeer density, potential impacts on these species between the present
time and 2080 were assessed. Over this period there was a net loss of open land within the current breeding range of most
bird species. Grazing reindeer were modelled as increasing the amount of open land retained for nine of the tundra bird species. 相似文献
156.
Enrico Kallmeier Christoph Breitkreuz Hubert Kiersnowski Marion Geißler 《Sedimentary Geology》2010,223(1-2):15-34
Facies analysis focussing on coarse-grained sediments has been carried out on more than 2500 m of drill cores from seven wells from southern margins of the North German Basin (NGB). The NGB forms a central element of the Southern Permian Basin (SPB). The wells exposed conglomerates and sandstones of the Rotliegend Grüneberg and Parchim Formations deposited in the Kotzen Basin and the Barnim Basin.17 lithofacies types have been grouped into six lithofacies associations. The studied successions are dominated by fluid gravity flow deposits (hyperconcentrated flows and stream flows) of alluvial fan and alluvial plain systems. Maximum particle size/bed thickness plots (MPS/BTh) support the interpretation as fluid gravity flow deposits. The MPS and BTh data have also been used to differentiate coarsening–thickening and fining–thinning trends of the fan systems.The dominance of water-rich mass flow processes together with sedimentary structures such as dewatering structures and outwashed tops suggests the presence of wet-type fans and plains under semi-humid to semi-arid seasonal climates in the central SPB. The investigated sediments show variation in clast composition subsequent to deep erosion processes on basin margins and changes of source areas. Synsedimentary normal faults and clastic dykes have been interpreted as indicators of tectonic activity of grabens itself and its frames. On a larger scale, then evolution from a half-graben to a graben is apparent for the Tuchen Sub-basin at least. The progradational/retrogradational cycles of the studied alluvial fan systems document combined local tectonic movements and influences of climatic changes. However, our data did not allow for a clear distinction between climatic and tectonic signals. Furthermore, a one-to-one correlation of fan cycles with depositional trends in the NGB basin centre would appear to be oversimplistic. 相似文献
157.
Constraints on gold and copper ore grades in porphyry-style Cu–Au ± Mo deposits are re-examined, with particular emphasis
on published fluid pressure and formation depth as indicated by fluid inclusion data and geological reconstruction. Defining
an arbitrary subdivision at a molar Cu/Au ratio of 4.0 × 104, copper–gold deposits have a shallower average depth of formation (2.1 km) compared with the average depth of copper–molybdenum
deposits (3.7 km), based on assumed lithostatic fluid pressure from microthermometry. The correlation of Cu/Au ratio with
depth is primarily influenced by the variations of total Au grade. Despite local mineralogical controls within some ore deposits,
the overall Cu/Au ratio of the deposits does not show a significant correlation with the predominant type of Cu–Fe sulfide,
i.e., chalcopyrite or bornite. Primary magma source probably contributes to metal endowment on the province scale and in some
individual deposits, but does not explain the broad correlation of metal ratios with the pressure of ore formation. By comparison
with published experimental and fluid analytical data, the observed correlation of the Cu/Au ratio with fluid pressure can
be explained by dominant transport of Cu and Au in a buoyant S-rich vapor, coexisting with minor brine in two-phase magmatic
hydrothermal systems. At relatively shallow depth (approximately <3 km), the solubility of both metals decreases rapidly with
decreasing density of the ascending vapor plume, forcing both Cu and Au to be coprecipitated. In contrast, magmatic vapor
cooling at deeper levels (approximately >3 km) and greater confining pressure is likely to precipitate copper ± molybdenum
only, while sulfur-complexed gold remains dissolved in the relatively dense vapor. Upon cooling, this vapor may ultimately
contract to a low-salinity epithermal liquid, which can contribute to the formation of epithermal gold deposits several kilometers
above the Au-poor porphyry Cu–(Mo) deposit. These findings and interpretations imply that petrographic inspection of fluid
inclusion density may be used as an exploration indicator. Low-pressure brine + vapor systems are favorable for coprecipitation
of both metals, leading to Au-rich porphyry–copper–gold deposits. Epithermal gold deposits may be associated with such shallow
systems, but are likely to derive their ore-forming components from a deeper source, which may include a deeply hidden porphyry–copper
± molybdenum deposit. Exposed high-pressure brine + vapor systems, or stockwork veins containing a single type of intermediate-density
inclusions, are more likely to be prospective for porphyry–copper ± molybdenum deposits. 相似文献
158.
Kai Berglar Christoph Gaedicke Dieter Franke Stefan Ladage Frauke Klingelhoefer Yusuf S. Djajadihardja 《Tectonophysics》2010,480(1-4):119-132
Based on new multi-channel seismic data, swath bathymetry, and sediment echosounder data we present a model for the interaction between strike-slip faulting and forearc basin evolution off north-western Sumatra between 2°N and 7°N. We examined seismic sequences and sea floor morphology of the Simeulue- and Aceh forearc basins and the adjacent outer arc high. We found that strike-slip faulting has controlled the forearc basin evolution since the Late Miocene. The Mentawai Fault Zone extends up to the north of Simeulue Island and was most probably connected farther northwards to the Sumatran Fault Zone until the end of the Miocene. Since then, this northern branch jumped westwards, initiating the West Andaman Fault in the Aceh area. The connection to the Mentawai Fault Zone is a left-hand step-over. In this transpressional setting the Tuba Ridge developed. We found a right-lateral strike-slip fault running from the conjunction of the West Andaman Fault and the Tuba Ridge in SSW-direction crossing the outer arc high. As a result, extrusion formed a marginal basin north of Simeulue Island which is tilted eastwards by uplift along a thrust fault in the west. The shift of strike-slip movement in the Aceh segment is accompanied by a relocation of the depocenter of the Aceh Basin to the northwest, forming one major Neogene unconformity. The Simeulue Basin bears two major Neogene unconformities, documenting that differences in subsidence evolution along the northern Sumatran margin are linked to both forearc-evolution related to subduction processes and to deformation along major strike-slip faults. 相似文献
159.
We present an effective achromatic imaging technique for diffraction-limited X-ray telescopes. For a common focal length,
independent optical sections of the aperture are dedicated to two or more spectral bands and optimized with respect to their
efficiency. For this purpose, we introduce the “achromatic gain” of an X-ray hybrid lens. Large-scale segmented and nested
apertures provide a promising implementation of that scheme. An optimized numerical example and astrophysical simulations
prove its capabilities for an energy range between 6 and 16 keV. 相似文献
160.
Winter synoptic-scale variability over the Mediterranean Basin under future climate conditions as simulated by the ECHAM5 总被引:3,自引:1,他引:2
Christoph Cornelius Raible Baruch Ziv Hadas Saaroni Martin Wild 《Climate Dynamics》2010,35(2-3):473-488
Changes of the winter climate in the Mediterranean Basin (MB) for future A2 conditions are investigated for the period 2071–2100 and compared with the control period 1961–1990. The analysis is based on time-slice simulations of the latest version of the ECHAM model. First, the control simulation is evaluated with reanalysis data. The emphasis is given to synoptic and large-scale features and their variability in the MB. The model is found to be capable of reproducing the main features of the MB and southern Europe in the winter season. Second, the A2 simulation is compared with the control simulation, revealing considerable changes of the synoptic variability. Focusing on the synoptic spatio-temporal scale aims to unfold the dynamic background of the climatic changes. The Mediterranean cyclones, which are individually detected and tracked, decrease by 10% in the Western Mediterranean (WM) whereas no significant change is found in the Eastern Mediterranean. The cyclone intensity is slightly reduced in the entire region. To understand these changes, the underlying dynamical background is analyzed. It is found that changes in baroclinicity, static stability, transformation from eddy kinetic energy to kinetic energy of the mean flow and stationary wave activity are significant in particular in the WM and the coastline of North Africa. The reduction of cyclonic activity severely impacts the precipitation mainly in the southern part of the WM. 相似文献