A numerical model of exhumation of the orogenic lower crust in the Bohemian Massif during the Variscan orogeny     

Petra Maierová  Ond?ej ?adek  Ondrej Lexa  Karel Schulmann 《Studia Geophysica et Geodaetica》2012,56(2):595-619

We present a numerical model of the main phase (370?C335 Ma) of the Variscan orogeny in the central part of the Bohemian Massif. The crustal deformation in our model is driven by radiogenic heating in the felsic lower crust, the lateral contraction of the Moldanubian domain due to convergence with the Saxothuringian plate (in the early stage of orogeny), and the indentation of the Brunovistulian basement into the weakened orogenic root (in the late stage). Our model explains the main geological events inferred from the geological record in the Moldanubian domain: formation of the orogenic plateau and onset of sedimentation at about 345 Ma, rapid exhumation of the orogenic lower crust at about 340 Ma and subsurface flow of crustal material (?? 335 Ma and later). The results of our modeling suggest that delamination of the lithosphere, often invoked to explain the high temperature metamorphism in the orogenic lower crust of the Bohemian Massif, is not the only physical mechanism which can transfer a sufficient amount of heat to the crust to trigger its overturn.  相似文献   

An integrated suspended sediment transport monitoring and analysis concept   总被引：1，自引：1，他引：0  

Marlene HAIMANN  Marcel LIEDERMANN  Petra LALK  Helmut HABERSACK 《国际泥沙研究》2014,29(2):135-148

A new integrated suspended sediment monitoring strategy applying direct and indirect technologies is presented.Optical sensors continuously record the turbidity at one point in the channel cross section close to the river bank and are calibrated by water samples taken close to the sensor.Additionally measurements are performed to establish the distribution of suspended sediment in a cross section（bottle samples combined with acoustic devices）.Using correction factors（probe and cross-sectional factor） these monitoring methods are combined and it is,thus,possible to fully document the temporal and spatial variability of the suspended sediment transport and to estimate the suspended sediment load for certain time periods.This monitoring strategy was implemented at various measurement sites in Austria as well as at the Hainburg Road Bridge site on the Danube River.It has already been successfully applied for three years at this measurement site and suspended sediment loads during high discharges up to a 15 year flood event have been monitored.To evaluate the new monitoring methods the results were compared with load estimation methods found in the literature including averaging and ratio estimators as well as rating curves.The results prove that with the new methodology,the temporal variability of the suspended sediment transport can be detected more accurately compared with the other methods.They also demonstrate that the additional consideration of the spatial distribution of the suspended sediment concentration in the cross section is crucial as the mean concentration in the cross section can significantly exceed the concentration near the banks,especially at large rivers like the Danube River.  相似文献   

Calibration/Data Assimilation Approach for Integrating GRACE Data into the WaterGAP Global Hydrology Model (WGHM) Using an Ensemble Kalman Filter: First Results   总被引：2，自引：0，他引：2  

Annette Eicker  Maike Schumacher  Jürgen Kusche  Petra Döll  Hannes Müller Schmied 《Surveys in Geophysics》2014,35(6):1285-1309

We introduce a new ensemble-based Kalman filter approach to assimilate GRACE satellite gravity data into the WaterGAP Global Hydrology Model. The approach (1) enables the use of the spatial resolution provided by GRACE by including the satellite observations as a gridded data product, (2) accounts for the complex spatial GRACE error correlation pattern by rigorous error propagation from the monthly GRACE solutions, and (3) allows us to integrate model parameter calibration and data assimilation within a unified framework. We investigate the formal contribution of GRACE observations to the Kalman filter update by analysis of the Kalman gain matrix. We then present first model runs, calibrated via data assimilation, for two different experiments: the first one assimilates GRACE basin averages of total water storage and the second one introduces gridded GRACE data at \(5^\circ\) resolution into the assimilation. We finally validate the assimilated model by running it in free mode (i.e., without adding any further GRACE information) for a period of 3 years following the assimilation phase and comparing the results to the GRACE observations available for this period.  相似文献   

Signal detectability in extreme precipitation changes assessed from twentieth century climate simulations   总被引：1，自引：0，他引：1  

Seung-Ki Min  Xuebin Zhang  Francis W. Zwiers  Petra Friederichs  Andreas Hense 《Climate Dynamics》2009,32(1):95-111

This study assesses the detectability of external influences in changes of precipitation extremes in the twentieth century, which is explored through a perfect model analysis with an ensemble of coupled global climate model (GCM) simulations. Three indices of precipitation extremes are defined from the generalized extreme value (GEV) distribution: the 20-year return value (P ₂₀), the median (P _m), and the cumulative probability density as a probability-based index (PI). Time variations of area-averages of these three extreme indices are analyzed over different spatial domains from the globe to continental regions. Treating all forcing simulations (ALL; natural plus anthropogenic) of the twentieth century as observations and using a preindustrial control run (CTL) to estimate the internal variability, the amplitudes of response patterns to anthropogenic (ANT), natural (NAT), greenhouse-gases (GHG), and sulfate aerosols (SUL) forcings are estimated using a Bayesian decision method. Results show that there are decisively detectable ANT signals in global, hemispheric, and zonal band areas. When only land is considered, the global and hemispheric detection results are unchanged, but detectable ANT signals in the zonal bands are limited to low latitudes. The ANT signals are also detectable in the P _m and PI but not in P ₂₀ at continental scales over Asia, South America, Africa, and Australia. This indicates that indices located near the center of the GEV distribution (P _m and PI) may give better signal-to-noise ratio than indices representing the tail of the distribution (P ₂₀). GHG and NAT signals are also detectable, but less robustly for more limited extreme indices and regions. These results are largely insensitive when model data are masked to mimic the availability of the observed data. An imperfect model analysis in which fingerprints are obtained from simulations with a different GCM suggests that ANT is robustly detectable only at global and hemispheric scales, with high uncertainty in the zonal and continental results.  相似文献   

Dew Formation,Eddy-Correlation Latent Heat Fluxes,and the Surface Energy Imbalance at Cabauw During Stable Conditions     

Stephan R. de Roode  Fred C. Bosveld  Petra S. Kroon 《Boundary-Layer Meteorology》2010,135(3):369-383

Observations collected between 2000 and 2008 at the Cabauw meteorological measurement platform in the Netherlands were conditionally sampled to select nights with stably stratified atmospheric conditions, clear skies and weak horizontal wind speeds (<3 m s⁻¹). For these conditions the eddy-correlation latent heat fluxes are found to be negligibly small, while the conditionally sampled surface energy balance exhibits a maximum residual. However, inspection of the specific humidities for these conditions reveals systematic drying trends that are a maximum at the lowest measurement level above the surface. These drying trends occur for any prevailing wind direction. Latent heat fluxes are calculated from the humidity budget equation and from a Penman-Monteith dewfall model, with the results suggesting that during clear, stable nights the observed latent heat fluxes as obtained from the eddy-correlation technique are erroneously small.  相似文献   

River management system development in Asia based on Data Integration and Analysis System (DIAS) under GEOSS     

Toshio Koike  Petra Koudelova  Patricia Ann Jaranilla-Sanchez  Asif Mumtaz Bhatti  Cho Thanda Nyunt  Katsunori Tamagawa 《中国科学:地球科学(英文版)》2015,58(1):76-95

This paper introduces the process of development and practical use implementation of an advanced river management system for supporting integrated water resources management practices in Asian river basins under the framework of GEOSS Asia water cycle initiative (AWCI). The system is based on integration of data from earth observation satellites and in-situ networks with other types of data, including numerical weather prediction model outputs, climate model outputs, geographical information, and socio-economic data. The system builds on the water and energy budget distributed hydrological model (WEB-DHM) that was adapted for specific conditions of studied basins, in particular snow and glacier phenomena and equipped with other functions such as dam operation optimization scheme and a set of tools for climate change impact assessment to be able to generate relevant information for policy and decision makers. In situ data were archived for 18 selected basins at the data integration and analysis system of Japan (DIAS) and demonstration projects were carried out showing potential of the new system. It included climate change impact assessment on hydrological regimes, which is presently a critical step for sound management decisions. Results of such three case studies in Pakistan, Philippines, and Vietnam are provided here.  相似文献   

Impact of Climate Change and Variability on Irrigation Requirements: A Global Perspective   总被引：7，自引：1，他引：7  

Petra Döll 《Climatic change》2002,54(3):269-293

Anthropogenic climate change does not only affect water resources but also water demand. Future water and food security will depend, among other factors, on the impact of climate change on water demand for irrigation. Using a recently developed global irrigation model, with a spatial resolution of 0.5° by 0.5°, we present the first global analysis of the impact of climate change and climate variability on irrigation water requirements. We compute how long-term average irrigation requirements might change under the climatic conditions of the 2020s and the 2070s, as provided by two climate models, and relate these changes to the variations in irrigation requirements caused by long-term and interannual climate variability in the 20th century. Two-thirds of the global area equipped for irrigation in 1995 will possibly suffer from increased water requirements, and on up to half of the total area (depending on the measure of variability), the negative impact of climate change is more significant than that of climate variability.  相似文献   

Beeinflusst die Strukturgüte von Fließgewässern das Vorkommen von Makrophyten?     

Barbara Passauer  Petra Meilinger  Arnulf Melzer  Susanne Schneider 《洁净——土壤、空气、水》2002,30(4):197-206

Does the Structural Quality of Running Waters Affect the Occurrence of Macrophytes? The morphological structure plays, besides e.g. nutrient concentration, an important role for the integrated assessment of running waters. This paper focuses on the relationship between structural quality and macrophyte vegetation. During summer 2000 structural quality according to LAWA, macrophyte vegetation, and selected habitat parameters were recorded in 135 mapping sections in running waters in Southern Germany. In streams of high structural diversity, generally higher species richness is expected than in rivers of low diversity of habitats. However, no significant differences in macrophyte species richness were detected between different classes of structural quality. In contrast, bryophytes alone showed a significant decrease in species richness with degradation of structural quality. The number of species of other macrophytes increased, respectively. The relationship between occurrence of macrophytes, structural quality, and other environmental variables was analysed using canonical correspondence analysis. Rivers of high structural quality mostly showed high flowing velocities and were heavily shaded. These environmental conditions, which characterize river types of mountainous regions, were predominantly tolerated by bryophytes. Vascular plants and charophytes generally prefer slowly flowing and unshaded habitats. River types exhibiting these environmental conditions often are more influenced by human activities and are more structurally degraded, respectively. With respect to these fundamental differences between river types, species richness of macrophytes and class of structural quality are not correlated when all types of rivers are taken into account. Type‐specific ecomorphological parameters, which conceal the differences in species richness caused by structural quality, are discussed. Structural degraded rivers can provide good environmental conditions for vascular plants and charophytes. To predict macrophyte species richness from structural quality, a differentiation of river types is essential.  相似文献   

An equation of state for roedderites, (K,Na)2Mg5[Si12O30], based on Knudsen cell mass spectrometry and synthesis of eifelite-roedderite crystalline solutions     

Petra Bruckmann  Niranjan D. Chatterjee  Werner Rammensee  Klaus Bielefeld 《Physics and Chemistry of Minerals》1993,20(5):362-368

Knudsen cell mass spectrometry has been applied to obtain activity (a _i) vs composition (X _i) data for 18 synthetic roedderites. (K, Na)₂Mg₅Si₁₂O₃₀, at temperatures between 900° and 1100° C. The samples were synthesized at 800° C and 1 kbar P _{H 2}O and characterized by X-ray powder diffractometry (XRD) and electron probe microanalysis (EPMA) prior to mass spectrometric activity measurement. The experimental a _i-X _i data have been smoothed, assuming for now the simplest possible model of a two-site K-Na mixing for this binary crystalline solution. Using the Margules formalism, and expressing the results in terms of one atom of K-Na mixing, the tentative equation of state is: W _G [J/mol] =-8704 -0.0067 · P, with P given in bar. The temperature-dependence of W _G could not be resolved due to its large uncertainty on the order of 2.8 kJ/mol. A more rigorous thermodynamic model for roedderites will have to be deferred until information on temperature-dependent K-Na disordering becomes available. Besides roedderites, single-phase eifelite-roedderite crystalline solutions have also been snythesized for the first time. They show a symmetric positive excess volume of mixing, with W _V [J/bar·mol]=0.1064±0.0021.  相似文献   

Estimating the Impact of Global Change on Flood and Drought Risks in Europe: A Continental, Integrated Analysis   总被引：11，自引：0，他引：11  

Bernhard Lehner  Petra Döll  Joseph Alcamo  Thomas Henrichs  Frank Kaspar 《Climatic change》2006,75(3):273-299

Most studies on the impact of climate change on regional water resources focus on long-term average flows or mean water availability, and they rarely take the effects of altered human water use into account. When analyzing extreme events such as floods and droughts, the assessments are typically confined to smaller areas and case studies. At the same time it is acknowledged that climate change may severely alter the risk of hydrological extremes over large regional scales, and that human water use will put additional pressure on future water resources. In an attempt to bridge these various aspects, this paper presents a first-time continental, integrated analysis of possible impacts of global change (here defined as climate and water use change) on future flood and drought frequencies for the selected study area of Europe. The global integrated water model WaterGAP is evaluated regarding its capability to simulate high and low-flow regimes and is then applied to calculate relative changes in flood and drought frequencies. The results indicate large ‘critical regions’ for which significant changes in flood or drought risks are expected under the proposed global change scenarios. The regions most prone to a rise in flood frequencies are northern to northeastern Europe, while southern and southeastern Europe show significant increases in drought frequencies. In the critical regions, events with an intensity of today's 100-year floods and droughts may recur every 10–50 years by the 2070s. Though interim and preliminary, and despite the inherent uncertainties in the presented approach, the results underpin the importance of developing mitigation and adaptation strategies for global change impacts on a continental scale.  相似文献