Univ.-Prof. Dr. Ferdinand Steinhauser — Zum 75. Geburtstag

Ohne Zusammenfassung     

Ein Diagramm zur Auswertung dest-Tests

Zusammenfassung Es wird ein Diagramm für dent-Test gegeben, aus dem man bei Kenntnis vonf, d undS allein entscheiden kann, ob die Stichprobe einent-Wert ergibt, der größer alst ist, oder nicht.

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Summary A graph is given for thet-test, by means of which one can decide whether the sample would give a value oft larger thant or not, only from the knowledge. off, d andS.

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Résumé L'auteur présente, pour le testt, un diagramme qui permet de dire si la valeur det dépasse celle det ou non, à la seule connaissance def, d etS.

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Postglacial climates inferred from a lake at treeline,southwest Yukon Territory,Canada

Pollen, chironomid, and ostracode records from a lake located at alpine treeline provide regional paleoclimate reconstructions from the southwest Yukon Territory, Canada. The pollen spectra indicate herbaceous tundra existed on the landscape from 13.6–11 ka followed by birch shrub tundra until 10 ka. Although Picea pollen dominated the assemblages after 10 ka, low pollen accumulation rates and Picea percentages indicate minimal treeline movement through the Holocene. Chironomid accumulation rates provide evidence of millennial-scale climate variability, and the chironomid community responded to rapid climate changes. Ostracodes were found in the late glacial and early Holocene, but disappeared due to chemical changes of the lake associated with changes in vegetation on the landscape. Inferred mean July air temperature, total annual precipitation, and water depth indicate a long-term cooling with increasing moisture from the late glacial through the Holocene. During the Younger Dryas (12.9–11.2 ka), cold and dry conditions prevailed. The early and mid-Holocene were warm and dry, with cool, wet conditions after 4 ka, and warm, dry conditions since the end of the Little Ice Age.     

Determination of Phobos’ rotational parameters by an inertial frame bundle block adjustment

A functional model for a bundle block adjustment in the inertial reference frame was developed, implemented and tested. This approach enables the determination of rotation parameters of planetary bodies on the basis of photogrammetric observations. Tests with a self-consistent synthetic data set showed that the implementation converges reliably toward the expected values of the introduced unknown parameters of the adjustment, e.g., spin pole orientation, and that it can cope with typical observational errors in the data. We applied the model to a data set of Phobos using images from the Mars Express and the Viking mission. With Phobos being in a locked rotation, we computed a forced libration amplitude of \(1.14^\circ \pm 0.03^\circ \) together with a control point network of 685 points.     

C‐band SAR backscatter characteristics of Arctic sea and land ice during winter

Abstract

Synthetic Aperture Radar (SAR) data has become an important tool for studies of polar regions, due to high spatial resolution even during the polar night and under cloudy skies. We have studied the temporal variation of sea and land ice backscatter of twenty‐four SAR images from the European Remote Sensing satellite (ERS‐1) covering an area in Lady Ann Strait and Jones Sound, Nunavut, from January to March 1992. The presence of fast ice in Jones Sound and glaciers and ice caps on the surrounding islands provides an ideal setting for temporal backscatter studies of ice surfaces. Sample regions for eight different ice types were selected and the temporal backscatter variation was studied. The observed backscatter values for each ice type characterize the radar signatures of the ice surfaces. This time series of twenty‐four SAR images over a 3‐month period provides new insights into the degree of temporal variability of each surface. Ice caps exhibit the highest backscatter value of ‐3.9 dB with high temporal variability. Valley glacier ice backscatter values decrease with decreasing altitude, and are temporally the most stable, with standard deviations of 0.08–0.10 dB over the 90‐day period.

First‐year ice and lead ice show a negative trend in backscatter values in time and a positive correlation of up to 0.59 with air temperature over the 90‐day period. For first‐year ice and lead ice, episodes of large temperature fluctuations (±12°C) are associated with rapid changes in backscatter values (±2 dB). We attribute the backscatter increase to a temperature‐induced increase in brine volume at the base of the snow pack. Multi‐year ice, conglomerate ice and shore ice are relatively stable over the 3‐month period, with a backscatter variation of only a few dBs. An observed lag time of up to three days between backscatter increase/decrease and air temperature can be attributed to the insulation effect of the snow cover over sea ice. The net range of the backscatter values observed on the most temporally stable surface, valley glacier ice, of about 0.30 dB indicates that the ERS‐1 SAR instrument exceeds the 1 dB calibration accuracy specified for the Alaska SAR Facility processor for the three winter months.     

Der Hagel im Wiener Becken

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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