Alpine climate during the Holocene: a comparison between records of glaciers,lake sediments and solar activity     

Samuel U. Nussbaumer  Friedhelm Steinhilber  Mathias Trachsel  Petra Breitenmoser  Jürg Beer  Alex Blass  Martin Grosjean  Albert Hafner  Hanspeter Holzhauser  Heinz Wanner  Heinz J. Zumbühl 《第四纪科学杂志》2011,26(7):703-713

The European Alps are very sensitive and vulnerable to climate change. Recent improvements in Alpine glacier length records and climate reconstructions from annually laminated sediments of Alpine Lake Silvaplana give the opportunity to investigate the relationship between these two data sets of Alpine climate. Two different time frames are considered: the last 500–1000 years as well as the last 7400 years. First, we found good agreement between the two different climate archives during the past millennium: mass accumulation rates and biogenic silica concentration are largely in phase with the glacier length changes of Mer de Glace and Unterer Grindelwaldgletscher, and with the records of glacier length of Grosser Aletschgletscher and Gornergletscher. Secondly, the records are compared with temporally highly resolved data of solar activity. The Sun has had a major impact on the Alpine climate variations in the long term, i.e. several centuries to millennia. Solar activity varies with the Hallstatt periodicity of about 2000 years. Hallstatt minima are identified around 500, 2500 and 5000 a. Around these times grand solar minima (such as the Maunder Minimum) occurred in clusters coinciding with colder Alpine climate expressed by glacier advances. During the Hallstatt maxima around 0, 2000 and 4500 a, the Alpine glaciers generally retreated, indicating a warmer climate. This is supported by archaeological findings at Schnidejoch, a transalpine pass in Switzerland that was only accessible when glaciers had retreated. On shorter timescales, however, the influence of the Sun cannot be as easily detected in Alpine climate change, indicating that in addition to solar forcing, volcanic influence and internal climate variations have played an important role. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Seismic upgrading of old masonry buildings by seismic isolation and CFRP laminates: a shaking-table study of reduced scale models   总被引：2，自引：2，他引：0  

Miha Tomaževič  Iztok Klemenc  Polona Weiss 《Bulletin of Earthquake Engineering》2009,7(1):293-321

The efficiency of improving the seismic resistance of old masonry buildings by means of seismic isolation and confining the structure with CFRP laminate strips has been investigated. Five models of a simple two-story brick masonry building with wooden floors without wall ties have been tested on the shaking table. The control model has been built directly on the foundation slab. The second model has been separated from it by a damp-proof course in the form of a PVC sheet placed in the bed-joint between the second and the third course, whereas the third model has been isolated by rubber isolators placed between the foundation slab and structural walls. Models four and five have been confined with CFRP laminate strips, simulating the wall ties placed horizontally and vertically at floor levels and corners of the building, respectively. One of the CFRP strengthened models has been placed on seismic isolators. Tests have shown that a simple PVC sheet damp-proof course cannot be considered as seismic isolator unless adequately designed. Tests have also shown that the isolators alone did not prevent the separation of the walls. However, both models confined with CFRP strips exhibited significantly improved seismic behavior. The models did not collapse even when subjected to significantly stronger shaking table motion than that resisted by the control model without wall ties.  相似文献   

Boundary layer aspects and elevated heat source effects of the Alps     

Dipl. Met. T. A. Hafner  Dr. M. E. Reinhardt  Dipl. Met. E. L. Weisel  Dipl. Met. H. P. Fimpel 《Meteorology and Atmospheric Physics》1987,36(1-4):61-73

Summary High pressure influence in the whole inner-ALPEX area on April 22, 1982 gave an opportunity for the ALPEX scientific task no. 6: To study the effects of differential radiative heating introduced by the alpine mountain range due to elevation, topographic features and albedo. Electra flight E-422 with its four-fold north-south, south-north flight tracks was especially devoted to study the diurnal variations of the atmospheric boundary layer and the airflow on both sides of the Alps along the Gotthard cross-section under strong inversion conditions. Using the flight technique of vertical zigzagging, a total of 24 vertical soundings have been completed along four traverses.Synoptic rawinsonde and surface data, digital satellite data and microbarograph data are used to examine the thermodynamical aspects of the diurnal development of the alpine heat low. The fine structure of the boundary layer is documented by cross-sectional analysis of the potential temperature, mixing ratio and the three wind components from the 1 Hz aircraft data along the traverses. In addition, 15 aircraft soundings have been selected to evaluate the vertical distribution of the turbulent variances and fluxes on both sides of the Alps. The differences of the structure and temporal evolution of the alpine boundary layer on the north and south side of the Alps, as well as the differences between the alpine boundary layer and the boundary layer over homogeneous terrain are significant and need further discussion.

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Aspekte der Grenzschicht und Effekte der erhöhten Wärmequelle der Alpen

Zusammenfassung Hochdruckeinfluß im gesamten inneren ALPEX-Gebiet am 22. April 1982 ermöglichte die ALPEX-Aufgabe Nr. 6: die Effekte unterschiedlicher Strahlungserwärmung, welche je nach Höhenlage, topographischen Gegebenheiten und Albedo der alpinen Gebirgskette verursacht werden, zu untersuchen. Der Electra-Flug E-422 mit seinen vierfachen Nord-Süd, Süd-Nord-Flugrouten beschäftigte sich besonders mit der Untersuchung der täglichen Veränderung der atmosphärischen Grenzschicht und der Luftströmung an beiden Seiten der Alpen entlang des Querschnittes beim Gotthard bei ausgeprägten Inversionen. Unter Verwendung der Flugtechnik des vertikalen Zickzacks wurden insgesamt 24 Vertikalsondierungen entlang von vier Schnittlinien durchgeführt.Synoptische Radiosonden- und Bodendaten sowie digitale Satelliten- und Mikrobarographendaten werden zur Untersuchung der thermodynamischen Aspekte der täglichen Entwicklung des alpinen Hitzetiefs verwendet. Die Feinstruktur der Grenzschicht wird durch Querschnittanalysen der potentiellen. Temperatur, des Mischungsverhältnisses und der drei Windkomponenten aus den vom Flugzeug entlang der Schnittlinien gewonnenen 1 Hz Daten dokumentiert. Darüber hinaus wurden 15 Flugzeugsondierungen ausgewählt, um die vertikale Verteilung der turbulenten Varianzen und Flüsse an beiden Seiten der Alpen zu beurteilen. Sowohl die Unterschiede in der Struktur und der zeitlichen Entwicklung der alpinen Grenzschicht an der nördlichen und der südlichen Seite der Alpen als auch die Unterschiede zwischen der alpinen Grenzschicht und der Grenzschicht über homogenem Gelände sind signifikant und erfordern eine weitere Diskussion.

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With 8 Figures  相似文献   

The electric field gradient at the position of copper in Cu2O and electronic charge density analysis by means of K-factors     

S. S. Hafner  S. Nagel 《Physics and Chemistry of Minerals》1983,9(1):19-22

The multipole moments of the charge density in Cu₂O are related to the electric field gradient (EFG) at the Cu position through crystallographic K-factors. The experimental EFG imposes certain restrictions on models for the charge distribution, which are discussed in detail. Nominal charges of +1 for Cu and ?2 for O on the basis of the ideal ionic model can be excluded. The sign of the field gradient is predicted to be negative.  相似文献   

The location of Fe³⁺ ions in forsterite (Mg₂SiO₄)     

S. Zeira  S.S. Hafner 《Earth and Planetary Science Letters》1974,21(2):201-208

The electron spin resonance spectrum of Fe³⁺ in a single crystal of forsterite was studied. Two distinct patterns of about equal intensities were observed which are due to Fe³⁺ at two distinct positions with 4a (M1)and4c (M2or Si) symmetry of Pbnm. The assignment of the 4c pattern to Fe³⁺ ions at the Si position cannot be excluded by symmetry but it is unlikely. The Hamiltonian parameters A and E/D are consistent with the conclusion that Fe³⁺ in this crystal is disordered over two distinct octahedral positions.  相似文献   

Hydrogeological and isotope mapping of the karstic River Savica in NW Slovenia     

Mihael Brenčič  Polona Vreča 《Environmental Earth Sciences》2016,75(8):651

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Microtremor study of site effects and soil-structure resonance in the city of Ljubljana (central Slovenia)   总被引：1，自引：0，他引：1  

Andrej Gosar  Janez Rošer  Barbara Šket Motnikar  Polona Zupančič 《Bulletin of Earthquake Engineering》2010,8(3):571-592

The city of Ljubljana is located in one of the three areas with the highest seismic hazard in Slovenia, and it is also the most densely populated. Site effects due to Quaternary sediments, which fill the up to 200 m-deep basin, are characteristic of the whole city area, but they can be especially strong in the southern part of Ljubljana, which is built on very soft lacustrine deposits. Existing microzonation studies of the city are inadequate, since there is a lack of borehole, geophysical and earthquake data. The microtremor horizontal-to-vertical spectral ratio (HVSR) method was therefore applied to a 200 m dense grid of free-field measurements over an area of 45 km² (1,223 measuring points) in order to assess the fundamental frequency of the sediments. The main difficulties in microtremor measurement arose from high levels of traffic and industrial noise, and from underground structures. Experimental conditions which can influence data quality, such as strong wind and water saturation of soil, were analysed. Very clear HVSR peaks were obtained in the entire southern part of the city, whereas in the northern part the site response is in general lower due to lower impedance contrast of gravel with the bedrock. The iso-frequency map of sediments shows a distribution in the range of 0.9–10 Hz. In the southern part of Ljubljana, sediment frequency correlates well with the thickness of soft sediments known from geophysical investigations and sparse drilling. Average amplitude of the HVSR peaks is considerably higher in the southern part (6.7 ± 2.4) than in the northern part (4.0 ± 2.0) of the city, indicating a high impedance contrast of lacustrine sediments with the bedrock. Microtremor measurements were also performed inside 122 buildings of various heights. We focused on important public buildings and selected blocks of flats and houses. To assess the longitudinal and transverse fundamental frequencies of each building, amplitude spectra and the spectral ratio between the upper floor and the basement were analysed for both directions. When one of these frequencies is close to a nearby free-field fundamental frequency, a potential soil-structure resonance is present. This was found in 12 of the measured buildings. Three of them are tall residential buildings (from 10 to 15 floors) with a fundamental frequency of 2–3 Hz, and nine of them are low-rise buildings (from 3 to 5 floors) with a fundamental frequency ranging from 3 to 4.5 Hz. Using the relationship between fundamental frequency and height, the typical height of buildings that might cause soil-structure resonance can be estimated at a given sediment frequency obtained from free-field measurements.  相似文献   

Displacement capacity of masonry buildings as a basis for the assessment of behavior factor: an experimental study   总被引：3，自引：2，他引：1  

Miha Tomaževič  Polona Weiss 《Bulletin of Earthquake Engineering》2010,8(6):1267-1294

The results of shaking table tests of a series of 1:5 scale masonry building models have been used for the assessment of values of structural behavior factor q for masonry structures, seismic force reduction factors proposed for the calculation of design seismic loads by Eurocode 8, European standard for the design of structures for earthquake resistance. Six models have been tested, representing prototype buildings of two different structural configurations and built with two different types of masonry materials. The study indicated that the reduction of seismic forces for the design depends not only on the type of masonry construction system, but also on structural configuration and mechanical characteristics of masonry materials. It has been also shown that besides displacement and energy dissipation capacity, damage limitation requirement should be taken into account when evaluating the values of behavior factor. On the basis of analysis of experimental results a conclusion can be made, that the values at the upper limit of the proposed range of values of structural behavior factor q for unreinforced and confined masonry construction systems are adequate, if pushover methods are used and the calculated global ductility of the structure is compared with the displacement demand. In the case where elastic analysis methods are used and significant overstrength is expected, the proposed values are conservative. However, additional research and parametric studies are needed to propose the modifications.  相似文献   

Poleward propagation of boreal summer intraseasonal oscillations in a coupled model: role of internal processes     

R. S. Ajayamohan  H. Annamalai  Jing-Jia Luo  Jan Hafner  Toshio Yamagata 《Climate Dynamics》2011,37(5-6):851-867

The study compares the simulated poleward migration characteristics of boreal summer intraseasonal oscillations (BSISO) in a suite of coupled ocean?Catmospheric model sensitivity integrations. The sensitivity experiments are designed in such a manner to allow full coupling in specific ocean basins but forced by temporally varying monthly climatological sea surface temperature (SST) adopted from the fully coupled model control runs (ES10). While the local air?Csea interaction is suppressed in the tropical Indian Ocean and allowed in the other oceans in the ESdI run, it is suppressed in the tropical Pacific and allowed in the other oceans in the ESdP run. Our diagnostics show that the basic mean state in precipitation and easterly vertical shear as well as the BSISO properties remain unchanged due to either inclusion or exclusion of local air?Csea interaction. In the presence of realistic easterly vertical shear, the continuous emanation of Rossby waves from the equatorial convection is trapped over the monsoon region that enables the poleward propagation of BSISO anomalies in all the model sensitivity experiments. To explore the internal processes that maintain the tropospheric moisture anomalies ahead of BSISO precipitation anomalies, moisture and moist static energy budgets are performed. In all model experiments, advection of anomalous moisture by climatological winds anchors the moisture anomalies that in turn promote the northward migration of BSISO precipitation. While the results indicate the need for realistic simulation of all aspects of the basic state, our model results need to be taken with caution because in the ECHAM family of coupled models the internal variance at intraseasonal timescales is indeed very high, and therefore local air?Csea interactions may not play a pivotal role.  相似文献   

Spatially smoothed seismicity modeling of seismic hazard in Slovenia     

Janez K. Lapajne  Barbara Sket Motnikar  Blaz Zabukovec  Polona Zupancic 《Journal of Seismology》1997,1(1):73-85

A progress report on the mapping effort for construction of a peak ground acceleration (PGA) map of Slovenia for 475-year return period for rock and firm soil is presented. The methodology is similar to that recently applied in Central and Eastern United States. It is based on historical seismicity spatially smoothed to different length scales. The procedure is described by Frankel (1995). He uses the characteristic earthquake recurrence relationship and in his firt version four different seismicity models. We also use four seismicity models. But instead of characteristic earthquake recurrence, we use the doubly truncated exponential magnitude-frequency relationship; no evidence of characteristic earthquakes in Slovenia has been found yet. Three of our models are similar to Frankel's first three models. Model 1 uses spatially smoothed activity rate based on magnitude 3.7 and above events since 1880. Model 2 deals with spatially smoothed activity rate based on magnitude 5.0 abd above events since 1690. Model 3 smoothes the observed activity over the entire region; it represents a uniform seismicity zone. Frankel skipped this model in his latest version (Frankel et al. 1996). In model 4, we introduce a new approach of calculating seismic activity rate taking into account released seismic energy. The ground motion attenuation model of Pugliese and Sabetta (1989) is used for all models. PGA maps for models 1, 2, 3 and 4 have been calculated, and a weighted mean map derived from them. A map of model 1 has been compared with the corresponding source zone map; the two maps do not differ significantly. A worst-case map derived from all four models has also been produced.  相似文献