The effects of spiral arms on the multi-phase ISM     

Anvar Shukurov  Graeme R. Sarson  Åke Nordlund  Boris Gudiksen  Axel Brandenburg 《Astrophysics and Space Science》2004,289(3-4):319-322

Statistical parameters of the ISM driven by thermal energy injectionsfrom supernova explosions have been obtained from 3D, nonlinear,magnetohydrodynamic, shearing-box simulations for spiral arm andinterarm regions. The density scale height obtained for the interarm regionsis 50% larger than within the spiral arms because of thehigher gas temperature. The filling factorof the hot gas is also significantly larger between the armsand depends sensitively on magnetic field strength.  相似文献   

On the elimination of seeing effects from solar intensity measurements     

A. Wittmann 《Solar physics》1971,21(1):237-239

  相似文献   

Probabilistic flood forecasting for a mountainous headwater catchment using a nonparametric stochastic dynamic approach     

Alexandre Cunha Costa  Axel Bronstert  David Kneis 《水文科学杂志》2013,58(1):10-25

Abstract

Hydrological models are commonly used to perform real-time runoff forecasting for flood warning. Their application requires catchment characteristics and precipitation series that are not always available. An alternative approach is nonparametric modelling based only on runoff series. However, the following questions arise: Can nonparametric models show reliable forecasting? Can they perform as reliably as hydrological models? We performed probabilistic forecasting one, two and three hours ahead for a runoff series, with the aim of ascribing a probability density function to predicted discharge using time series analysis based on stochastic dynamics theory. The derived dynamic terms were compared to a hydrological model, LARSIM. Our procedure was able to forecast within 95% confidence interval 1-, 2- and 3-h ahead discharge probability functions with about 1.40 m³/s of range and relative errors (%) in the range [–30; 30]. The LARSIM model and the best nonparametric approaches gave similar results, but the range of relative errors was larger for the nonparametric approaches.

Editor D. Koutsoyiannis; Associate editor K. Hamed

Citation Costa, A.C., Bronstert, A. and Kneis, D., 2012. Probabilistic flood forecasting for a mountainous headwater catchment using a nonparametric stochastic dynamic approach. Hydrological Sciences Journal, 57 (1), 10–25.  相似文献   

Crystal scale anatomy of a dying supervolcano: an isotope and geochronology study of individual phenocrysts from voluminous rhyolites of the Yellowstone caldera   总被引：3，自引：3，他引：0  

Kathryn E. Watts  Ilya N. Bindeman  Axel K. Schmitt 《Contributions to Mineralogy and Petrology》2012,164(1):45-67

A voluminous (>600 km³) and long-lived (~520–75 ka) phase of rhyolitic eruptions followed collapse of the Yellowstone caldera 640 ka. Whether these eruptions represent a dying cycle, or the growth of a new magma chamber, remains an important question. We use new U–Th zircon ages and δ¹⁸O values determined by ion microprobe, and sanidine Pb isotope ratios determined by laser ablation, to investigate the genesis of voluminous post-caldera rhyolites. The oldest post-caldera rhyolites, erupted between ~520 and 470 ka, exhibit extreme age and oxygen isotopic heterogeneity, requiring derivation from individual parcels of low-δ¹⁸O melts. We find a progressive increase in zircon homogeneity for rhyolite eruptions from ~260 to 75 ka, with homogeneous low-δ¹⁸O zircon values of 2.7–2.8‰ that are in equilibrium with low-δ¹⁸O host melts for the majority of the youngest eruptions. New sanidine Pb isotope data define separate arrays for post-caldera rhyolites and the caldera-forming tuffs that preceded them, indicating that they were not sourced from a mushy Lava Creek Tuff batholith that remained after caldera collapse. Rather, our new age and isotopic data indicate that the post-caldera rhyolites were generated by remelting of a variety of intracaldera source rocks, consisting of pre-Lava Creek Tuff volcanic and plutonic rocks and earlier erupted post-Lava Creek Tuff rhyolites. Batch assembly of low-δ¹⁸O melts starting at ~260 ka resulted in progressive homogenization, followed by differentiation and cooling up until the last rhyolite eruption ~75 ka, a trend that we interpret to be characteristic of a dying magma reservoir beneath the Yellowstone caldera.  相似文献   

Potentials and constraints of different types of soil moisture observations for flood simulations in headwater catchments     

Axel Bronstert  Benjamin Creutzfeldt  Thomas Graeff  Irena Hajnsek  Maik Heistermann  Sibylle Itzerott  Thomas Jagdhuber  David Kneis  Erika Lück  Dominik Reusser  Erwin Zehe 《Natural Hazards》2012,60(3):879-914

Flood generation in mountainous headwater catchments is governed by rainfall intensities, by the spatial distribution of rainfall and by the state of the catchment prior to the rainfall, e.g. by the spatial pattern of the soil moisture, groundwater conditions and possibly snow. The work presented here explores the limits and potentials of measuring soil moisture with different methods and in different scales and their potential use for flood simulation. These measurements were obtained in 2007 and 2008 within a comprehensive multi-scale experiment in the Weisseritz headwater catchment in the Ore-Mountains, Germany. The following technologies have been applied jointly thermogravimetric method, frequency domain reflectometry (FDR) sensors, spatial time domain reflectometry (STDR) cluster, ground-penetrating radar (GPR), airborne polarimetric synthetic aperture radar (polarimetric SAR) and advanced synthetic aperture radar (ASAR) based on the satellite Envisat. We present exemplary soil measurement results, with spatial scales ranging from point scale, via hillslope and field scale, to the catchment scale. Only the spatial TDR cluster was able to record continuous data. The other methods are limited to the date of over-flights (airplane and satellite) or measurement campaigns on the ground. For possible use in flood simulation, the observation of soil moisture at multiple scales has to be combined with suitable hydrological modelling, using the hydrological model WaSiM-ETH. Therefore, several simulation experiments have been conducted in order to test both the usability of the recorded soil moisture data and the suitability of a distributed hydrological model to make use of this information. The measurement results show that airborne-based and satellite-based systems in particular provide information on the near-surface spatial distribution. However, there are still a variety of limitations, such as the need for parallel ground measurements (Envisat ASAR), uncertainties in polarimetric decomposition techniques (polarimetric SAR), very limited information from remote sensing methods about vegetated surfaces and the non-availability of continuous measurements. The model experiments showed the importance of soil moisture as an initial condition for physically based flood modelling. However, the observed moisture data reflect the surface or near-surface soil moisture only. Hence, only saturated overland flow might be related to these data. Other flood generation processes influenced by catchment wetness in the subsurface such as subsurface storm flow or quick groundwater drainage cannot be assessed by these data. One has to acknowledge that, in spite of innovative measuring techniques on all spatial scales, soil moisture data for entire vegetated catchments are still today not operationally available. Therefore, observations of soil moisture should primarily be used to improve the quality of continuous, distributed hydrological catchment models that simulate the spatial distribution of moisture internally. Thus, when and where soil moisture data are available, they should be compared with their simulated equivalents in order to improve the parameter estimates and possibly the structure of the hydrological model.  相似文献   

Joint implementation and EU accession countries     

Mercedes Fernndez Armenteros  Axel Michaelowa 《Global Environmental Change》2003,13(4):269-275

The EU accession countries have a high potential for low cost greenhouse gas emission reduction. As they cannot join the “bubble” agreement for the first commitment period of the Kyoto Protocol, project-based Joint Implementation (JI) could be a powerful strategy to integrate them into the EU climate policy strategy. An important question is whether the acquis communautaire will be used to define the baseline for the calculation of emission reductions from JI projects. A problem is that the grace periods for several environmental sectors differ considerably among countries. The EU should help accession countries to establish a predictable legal framework for JI preventing in this way the current legal uncertainty regarding JI procedures.  相似文献   

Beginnings of Regular Seismic Service and Research in the Austro-Hungarian Monarchy: Part I     

Kozák  Jan  Plešinger  Axel 《Studia Geophysica et Geodaetica》2003,47(1):99-119

The paper mentions the first attempts of European savants and scientists in the past centuries to study in a more systematic way the phenomenon named an earthquake. Discussed in this context are the activities developed in the second half of the 19th century by Viennese and other Austro-Hungarian physicists, geologists, geographers and specialists in geomagnetism, geodesy and other geo-disciplines with the aim to initiate regular seismological research in the Monarchy. These efforts resulted in the idea to organize an effective seismic survey which would supply the researchers with continuous earthquake data, first on the macroseismic level, later on the basis of instrumental observations.We speculate upon the reasons which stimulated such a difficult and long-term project at that time and discuss the impact of the new ideas on one particular region of the Monarchy—the territory of Bohemia the seismic activity of which had been described as low or moderate. We link these efforts to the all-European endeavour of the time to promote (up to that time only sporadic) earthquake observations and studies to the rank of systematic seismological research.The paper deals with these activities as they had been accomplished by the end of the 19th century. In Part II, the continuation of the efforts in the first decade of the 20th century will be discussed. The pioneering works reported in both papers quite naturally created a solid fundament for the later development of seismology in former Czechoslovakia and in the present Czech Republic.  相似文献   

Beginnings of Regular Seismic Service and Research in the Austro-Hungarian Monarchy: Part II     

Plešinger  Axel  Kozák  Jan 《Studia Geophysica et Geodaetica》2003,47(4):757-791

We closed the preceding part of our paper with the statements that a regular macroseismic service of unprecedented effectivity had been successfully established in the Austrian part of the Monarchy in 1896-1899, and that first continuous instrumental observations had been started at the seismic stations in Ljubljana, Trieste and Kremsmünster in 1897, 1898 and 1899, respectively. In the present part we report how the macroseismic service performed its task from the beginning of the 20^th century until the outbreak of World War I, we briefly summarize the beginnings and development of observational seismology in the Hungarian part of the Monarchy, and we inform the reader about the state of European seismometry at the time of establishment of the first stations of the Austro-Hungarian seismographic network.Main topics of the present paper are the history of the development, the principles and properties of the instruments, and the milestones in the interpretation of instrumental observations in both parts of the Monarchy in 1897-1914. The wealth of information extracted from over seventy original papers and books of geoscientists of the time is summarized in the form of two, to a large extent self explaining tables. In Table 1 the altogether seventeen seismic stations gradually established in the Austrian as well as Hungarian parts of the Monarchy in 1897-1914 are ordered chronologically according to the date of initiation of regular measurements at them, and the instruments by which the stations were originally equipped and later successively upgraded are specified. The most important facts about progress in the instrumentation and in the analysis, interpretation and archivation of the observational material are summed up in the last column of Table 1. The principles of the altogether sixteen different types of seismic instruments that were in operation at the stations of the Austro-Hungarian network in the discussed period are explained and their basic technical parameters are specified in Table 2. Those instrumental problems, those moments in the methodology of interpretation of the instrumental observations, and the contributions of those scientists who most decisively influenced the progress of Austro-Hungarian seismology in 1897-1914 are commented in more detail in the text.At the end of the first decade of the 20^th century, the instrumentation of the stations of the Austro-Hungarian seismographic network as well as the scientific erudition and publication activities of the station directors and involved geosavants, especially of A. Belar, H. Benndorf, R. Kövesligethy, V. Láska, E. Mazelle, A. and S. Mohorovii and A. Réthly, had reached a standard comparable with that of analogous activities in Italy and Germany. The well developed Austrian macroseismic service gradually disintegrated during World War I. After the war, seismology progressed in the newly constituted states Czechoslovakia, Poland and Yugoslavia in broader, all-European collaboration.  相似文献   

Reviews     

Peter R. Odell  Seiya Uyeda  V. P. Zenkovich  C. Koeman  Johannes Ulrich  Maurice K.-Seguin  K. Gerke  U. Vetter  G. T. W. Wittmann  H. J. Habing  J. Gentilli 《GeoJournal》1977,1(1):95-100

  相似文献   

Manganese(II) oxidation driven by lateral oxygen intrusions in the western Black Sea     

Axel Schippers  Lev N. Neretin  Gaute Lavik  Falk Pollehne 《Geochimica et cosmochimica acta》2005,69(9):2241-2252

Mn(II) oxidation in the suboxic zone of the water column was studied at four stations in the western Black Sea. We measured Mn(II) oxidation rates using ⁵⁴Mn tracer and tested the hypothesis of alternative oxidants for Mn(II) other than dissolved oxygen. In anoxic incubation experiments with water from different depths of the chemocline, Mn(II) was not oxidized by nitrite, nitrate, or iodate. In the presence of light, Mn(II) also was not oxidized under anoxic conditions as well. Anaerobic Mn(II) oxidizing microorganisms could not be enriched. In oxic incubation experiments, the addition of alternative oxidants did not significantly increase the Mn(II) oxidation rate. The lack of an anaerobic Mn(II) oxidation in our experiments does not unambiguously prove the absence of anaerobic Mn(II) oxidation in the Black Sea but suggests that dissolved oxygen is the only oxidant for biologically catalyzed Mn(II) oxidation. Lateral intrusions of modified Bosphorus water were shown to be the main mechanism providing dissolved oxygen in the suboxic and the upper anoxic zones and explaining observed Mn(II) oxidation rates. Maximum in situ Mn(II) oxidation rates in the suboxic zone were 1.1 nM Mn(II) per h in the central Black Sea, 25 nM Mn(II) per h on the Romanian continental slope and 60 nM Mn(II) per h on the Anatolian continental slope. These rates correlate with the amount of particulate Mn and the number of Mn-oxide particles and are in agreement with rates measured 13 yr before. Our study highlights the importance of lateral intrusions of oxygen for the ventilation of the suboxic zone and the anoxic interior and for the regulation of different oxidation-reduction processes in the chemocline, including Mn(II) oxidation, which may be significant for other anoxic basins as well.  相似文献