Der Hagel im Wiener Becken     

Konrad Cehak 《Theoretical and Applied Climatology》1958,9(3-4):340-359

Zusammenfassung An Hand der Schadenstatistik 1952–1956 der österreichischen Hagelversicherung wurden Häufigkeitsverteilungen der Hagelschäden im Wiener Becken berechnet. Für längere Zeitabschnitte wurde die jährliche Hagelwahrscheinlichkeit in Wien als Poisson-Verteilung dargestellt. Eine Karte bringt die örtliche Verteilung der Hagelgefahr im Wiener Becken, wobei sich zwei besonders gefährdete Gebiete zeigen. Im weiteren wird gezeigt, daß Hagelfälle besonders bei den GroßwetterlagenHN, TK, TR, Vb undTB auftreten. Die südöstliche Höhenströmung in der 500 mb-Fläche wird als besonders hagelbegünstigend erkannt.Für Tage mit verbreiteter Hageltätigkeit wied eine mittlere Aufstiegskurve berechnet. Mittels des Thetagramms wird untersucht, welche Luftmassen bei besonders hagelfördernden Großwetterlagen und Höhenströmungen auftreten. Es zeigt sich, daß fast immer Tropikluft, die in den unteren Schichten überhitzt wird, an den großen Hagelfällen beteiligt ist.

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Summary On the basis of the statistics of damages of the Austrian Hail Insurance Company, 1952–1956, frequency distributions of hail-damages in the basin of Vienna were evaluated. For longer periods the annual probability of hail in Vienna was expressed by a Poisson-distribution. A map represents the local distribution of hail-risk in the basin of Vienna, showing two regions especially endangered. Further it has been shown that hail-storms occur expecially with the weather situationsHN, TK, TR, Vb andTB. The upper wind from southeast has been realized to be especially promoting for the occurrence of hail.A mean sounding was evaluated for days with wide-spread hail-activity. By means of the thetagramm it has been investigated which air-masses occur in weather situations and with upper winds which promote the falling of hail. It turns out that nearly always tropical air-masses, being superheated in layers near the ground, participate in large hail-storms.

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Résumé S'appuyant sur la statistique de dégâts 1952/56 de l'assurance autrichienne contre la grêle, l'auteur a calculé la distribution de fréquence de ces dégâts dans le bassin viennois. La probabilité de grêle à Vienne pour de longues périodes s'exprime par une distribution de Poisson. Une carte représente la répartition géographique du danger de grêle dans le bassin viennois; elle met en évidence deux régions particulièrement menacées. Les chutes de grêle se produisent plus fréquemment lors des situations météorologiquesHN, TK, TR, Vb etTB; le courant de Sud-Est au niveau de la surface de 500 mb apparaît comme particulièrement favorable à la grêle.On établit une courbe d'état aérologique moyenne pour les jours à chutes de grêle étendues. L'étude des thétagrammes permet de préciser quelles sont les masses d'air présentes lors des conditions favorables à la grêle; on constate que c'est presque toujours l'air tropical surchauffé dans les couches basses.

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Mit 6 Textabbildungen  相似文献   

Boron isotopes as an artificial tracer     

Quast KW  Lansey K  Arnold R  Bassett RL  Rincon M 《Ground water》2006,44(3):453-466

A field study was conducted using a combination of intrinsic and artificial tracers to estimate travel times and dilution during transport of infiltrate from a reclaimed water infiltration basin to nearby monitoring wells. A major study objective was to validate boric acid enriched in (10)B as an artificial tracer. Basin 10E at the Rio Hondo Spreading Grounds in Whittier, California, was the site of the test. The basin normally receives a mixture of treated municipal waste water, purchased State Project water, and local runoff from the San Gabriel River. Approximately 3.5 kg of (10)B-enriched boric acid was dispersed among 2.05 x 10(5) m(3) of basin water to initiate the experiment. The resultant median delta(11)B in the infiltration basin was -71 per thousand. Prior to tracer addition, the basin water had an intrinsic delta(11)B of +2 per thousand. Local monitoring wells that were used to assess travel times had delta(11)B values of +5 per thousand and +8 per thousand at the time of tracer addition. Analytic results supported an assumption that boron is conserved during ground water transport and that boron enriched in (10)B is a useful artificial tracer. Several intrinsic tracers were used to reinforce the boric acid tracer findings. These included stable isotopes of oxygen (delta(18)O) and hydrogen (deltaD), sulfate concentration, and the boron to chloride ratio. Xenon isotopes, (136)Xe and (124)Xe, also supported boron isotope results. Xenon isotopes were added to the recharge basin as dissolved gases by investigators from the Lawrence Livermore National Laboratory.  相似文献   

Thermal convection in the porous methane-soaked regolith of Titan: Investigation of stability     

Leszek Czechowski  Konrad Kossacki 《Icarus》2009,202(2):599-606

Titan is the only body, other than the Earth where liquid is present on the surface. In the present work we consider behavior of methane in the pores of Titan's regolith. Using numerical model we investigate quantitative conditions necessary for the onset of convection. We have found that the methane convection in Titan's regolith is possible. It can be expected in regions where the regolith has sufficiently high porosity, independently of the geothermal heat flux.  相似文献   

GETEMME—a mission to explore the Martian satellites and the fundamentals of solar system physics     

Jürgen Oberst  Valéry Lainey  Christophe Le Poncin-Lafitte  Veronique Dehant  Pascal Rosenblatt  Stephan Ulamec  Jens Biele  J?rn Spurmann  Ralph Kahle  Volker Klein  Ulrich Schreiber  Anja Schlicht  Nicolas Rambaux  Philippe Laurent  Beno?t Noyelles  Bernard Foulon  Alexander Zakharov  Leonid Gurvits  Denis Uchaev  Scott Murchie  Cheryl Reed  Slava G. Turyshev  Jesus Gil  Mariella Graziano  Konrad Willner  Kai Wickhusen  Andreas Pasewaldt  Marita W?hlisch  Harald Hoffmann 《Experimental Astronomy》2012,34(2):243-271

GETEMME (Gravity, Einstein??s Theory, and Exploration of the Martian Moons?? Environment), a mission which is being proposed in ESA??s Cosmic Vision program, shall be launched for Mars on a Soyuz Fregat in 2020. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive Laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine Laser range measurements to the reflectors on Phobos and Deimos. Also, asynchronous two-way Laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellite system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter ?? as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame.  相似文献   

X-rays from Venus observed with Chandra     

Konrad Dennerl 《Planetary and Space Science》2008,56(10):1414-1423

X-ray observations of Venus are so challenging that the first detection of Venusian X-rays succeeded only in January 2001, with the Chandra satellite. The X-rays from Venus were found to result from fluorescent scattering of solar X-rays in the Venusian thermosphere. An additional component, caused by charge exchange of highly charged heavy ions in the solar wind with atoms in the Venusian exosphere, was suspected, but could not be unambiguously detected. This was hampered by the fact that the observation occurred during solar maximum, when the solar X-ray flux is highest. In order to investigate the presence of an additional charge exchange component, Venus was observed again in March 2006 and October 2007 with Chandra, taking advantage of the fact that the solar X-ray flux had decreased considerably on its way to solar minimum. In fact, these subsequent observations were able to show that also the Venusian exosphere is emitting X-rays, due to its interaction with the solar wind. Here an overview of all the existing X-ray observations of Venus is presented, including first results from the most recent one, which took place after the arrival of Venus Express, providing the first ever opportunity to combine a remote X-ray observation of a planetary exosphere with simultaneous in situ measurements of the solar wind.  相似文献   

Microlensing by cosmic strings     

Konrad Kuijken  Xavier Siemens  Tanmay Vachaspati 《Monthly notices of the Royal Astronomical Society》2008,384(1):161-164

We consider the signature and detectability of gravitational microlensing of distant quasars by cosmic strings. Because of the simple image configuration such events will have a characteristic lightcurve, in which a source would appear to brighten by exactly a factor of 2, before reverting to its original apparent brightness. We calculate the optical depth and event rate, and conclude that current predictions and limits on the total length of strings on the sky imply optical depths of ≲ 10⁻⁸ and event rates of fewer than one event per 10⁹ sources per year. Disregarding those predictions but replacing them with limits on the density of cosmic strings from the cosmic microwave background fluctuation spectrum, leaves only a small region of parameter space (in which the sky contains about 3 × 10⁵ strings with deficit angle of the order of 0.3 milli-seconds) for which a microlensing survey of exposure 10⁷ source years, spanning a 20–40-year period, might reveal the presence of cosmic strings.  相似文献   

Comet 9P/Tempel 1: Sublimation beneath the dust cover     

Konrad J. Kossacki  Slawomira Szutowicz 《Icarus》2008,195(2):705-724

In the current work we analyze properties of the dust mantle, its thickness and thermal conductivity, necessary to reproduce observed rate of water production of Comet 9P/Tempel 1. For this purpose we considered simplified shape of the comet nucleus approximated by the symmetric prolate ellipsoid with smooth surface. We have performed simulations, using models with dust mantle of the thickness either constant, but nonuniform (Model A), or evolving (Model B). The simulated profiles of water production versus time were compared with observations. In addition, we compared the calculated surface temperature with the real temperatures derived from IR observations (the Deep Impact mission). This new double-stage verification procedure, shows that our model A is a good representation for the nucleus of Comet Tempel 1. This indicates, that the dust mantle thickness should be nonuniform, but does not change significantly with time. We show, that reproducing observed high temperatures of the nucleus requires dust mantle, that is almost everywhere thick and has extremely low thermal inertia. The latter should be close to zero as already predicted by others. The agreement between the simulated and measured water production can be obtained when the dust is regionally thin and has the thermal inertia higher than average, according to our simulations about 100 W s^1/2 K⁻¹ m⁻². Such regions should be located in the south hemisphere of the nucleus.  相似文献   

A high resolution proxy-climate record from an arctic lake with annually-laminated sediments on Devon Island, Nunavut, Canada   总被引：1，自引：0，他引：1  

K. Gajewski  P. B. Hamilton  R. McNeely 《Journal of Paleolimnology》1997,17(2):215-225

Sediments from a 3 ha lake (75 °34.34N, 89 °18.55W) from the coastal region of northern Devon Island, Nunavut, Canada, contain discrete laminations in the deepest part of the basin. The laminations are varves as indicated by the correspondence between counts and thickness measurements of the couplets and ²¹⁰Pb dating. A 14 cm core representing 150 years of sedimentation contained laminated couplets consisting of a lighter inorganic layer with a higher percentage of calcium and magnesium, alternating with fine darker bands, typically more cohesive, and comprising higher proportions of silica and carbon. A reddish oxidation zone with higher iron and aluminum frequently separates the laminations. The dark layer represents a biogenic component deposited in summer and is made cohesive by bacterial filaments among the other particles. The light inorganic layer represents clastic deposition from allochthonous sources. Deposition rates were relatively consistent through the core with an increase in varve thickness in the 1950s. Diatom concentrations in the sediments increased by two orders of magnitude in this century, with major increases in the 1920s and 1950s. The increase in varve thickness and diatom abundance coincides with an increase in summer melt percentage in an ice core from the Devon Island Ice Cap (Koerner, 1977). The relatively high sedimentation rate (0.15 cm yr^-1) coupled with the consistency of deposition makes this lake a significant indicator for recent climate changes of the Canadian Arctic Archipelago.  相似文献   

Long-term monitoring of wall paintings affected by soluble salts   总被引：1，自引：0，他引：1  

Konrad?ZehnderEmail author 《Environmental Geology》2007,52(2):353-367

Long-term monitoring of wall paintings in historical monuments aims at clarifying involved decay processes and at the same time controlling effects of interventions for conservation. Monitored decay processes relate to the crystallisation of various salts – particularly of nitronatrite and gypsum – from hygroscopic solutions accumulated in the zone of ground moisture. The salts crystallise in response to climatic variations and other environmental changes. Measures for conservation such as protection from water infiltration, reduction of heating temperature and reduction of surface salt accumulation cause a significant slow-down but not a stop of decay. The particular dynamics and causes of remaining slow decay processes are described on three sites in Switzerland: the convent church of Müstair, the crypt in the cathedral of Basel and the crypt in the Grossmünster church of Zürich.  相似文献   

The pattern speed of the bar in NGC 4596     

Joris Gerssen  Konrad Kuijken  Michael R. Merrifield 《Monthly notices of the Royal Astronomical Society》1999,306(4):926-930

The pattern speed is a defining parameter of any barred galaxy. A large number of model-dependent techniques have therefore been developed to derive the pattern speed. However, the only model-independent technique for measuring this quantity – the Tremaine–Weinberg method – has hitherto been applied to just one case, the SB0 galaxy NGC 936. In this paper, we apply the technique to a second system, the SBa galaxy NGC 4596. The resulting estimate for the pattern speed is Ω_p=52±13 km s⁻¹ kpc⁻¹. This result is corroborated by a spectrum obtained along the major axis of the bar in this system. The corotation radius associated with this pattern speed lies just beyond the end of the bar indicating a fast bar. Combining the bar major-axis spectra with data obtained from a Hubble Space Telescope WFPC2 image, we also find strong evidence for a nuclear disc.  相似文献