On temperature initialization in primitive equation forecast models

Four procedures of specifying model initial temperature were described and tested in the present study. It was found that the use of observed temperatures along with a proper vertical interpolation scheme was not only acceptable, but produced less error than the use of temperatures derived from geopotential height through the hydrostatic equation did. Use of the difference form of the hydrostatic equation would produce unacceptable errors in the initial temperatures, unrealistic horizontal and vertical distribution of temperature, and these errors would influence the calculation of the pressure gradient force, resulting in substantial, artificial disturbances within the model domain.In addition, an approach to check the initial data was described. Taking advantage of the fact that the geostrophic wind in sigma coordinates should be nondivergent, geopotential height and temperature were used to calculate the pressure gradient force terms and an initial divergence of the geostrophic wind. This approach can he used for comparing different initialization schemes for identical input data.     

GNSS processing at CODE: status report

Since May 2003, the Center for Orbit Determination in Europe (CODE), one of the analysis centers of the International GNSS Service, has generated GPS and GLONASS products in a rigorous combined multi-system processing scheme, which promises the best possible consistency of the orbits of both systems. The resulting products, in particular the satellite orbits and clocks, are easily accessible by the user community. In the first part of this article, we focus on the generation of the combined global products at CODE, where we put emphasis not only on accuracy, but also on completeness. We study the impact of GLONASS on the CODE products, and the benefit of using them. Last, but not least, we introduce AGNES (Automated GNSS Network for Switzerland), a regional tracking network of small extensions (roughly 400 km East–West, 200 km North–South), which consequently tracks all GNSS satellites and analyzes their measurements using the CODE products.     

Fission-Track-Alter von Durango-Apatit,Mexiko

Spontaneous and induced fission tracks in apatite were revealed by etching with HNO₃ and used for fission track dating. The fission track age of specimens known as Durango-Apatite was found to be (36.3±3.5) · 10⁶ a.

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Die Untersuchungen wurden mit Mitteln des Österreichischen Fonds zur Förderung der wissenschaftlichen Forschung durchgeführt.

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Den Herrn Prof. Dr. M. Higatsberger und Dipl.-Ing. A. Burtscher von der Studiengesellschaft für Atomenergie in Seibersdorf verdanken wir die sorgfältige Durchführung der Bestrahlung der Proben.     

Maximale Böigkeitsverhältnisse in Innsbruck

Zusammenfassung Häufigkeitsverteilungen der täglichen Maximalböen, geordnet nach Geschwindigkeit und Eintrittszeit, werden für Föhn, Gewitter und Wetterlagen ohne Föhn und Gewitter gesondert diskutiert. Der Jahresgang der täglichen und der monatlichen Maximalböen wird mit dem des Windweges pro Stunde verglichen.

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Summary Frequency distributions after speed and time of occurrence of the daily maximum gusts are discussed separately for days with foehn or thunderstorm and for days without foehn or thunderstorm. A comparison is made between the annual variation of daily and monthly maximum gusts and that of the maximum hourly run of the wind.

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Résumé L'autor discute la distribution de fréquence des rafales maxima de vent, par jour, classées par vitesse et heure d'apparition, pour le foehn et l'orage ainsi qu'en l'absence de ceux-ci. Comparaison de la marche annuelle des maxima journaliers et mensuels avec le parcours de vent par heure.

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Mit 5 Textabbildungen     

Early lunar differentiation: 4.42-AE-old plagioclase clasts in Apollo 16 breccia 67435

We report on a⁴⁰Ar-³⁹Ar study of the Apollo 16 breccia 67435 and present ages of five samples representing matrix, lithic clasts and plagioclase clasts. While the matrix age spectrum does not have a well-defined plateau, the two lithic clasts gave plateau ages of 3.96 and 4.04 AE. Since all samples had apparent ages of ～1 AE in the fractions ≤600°C extraction temperature, the breccia might have been assembled in a rather mild process at about that time or even more recently out of material with different metamorphic ages. The two plagioclase samples, of which one was a single 9-mg mineral clast and the other a 15-mg composite of several clasts, also have ages of ～1 AE in the low-temperature release fractions, but are apparently undisturbed by any ～4-AE events since they both have well-defined plateaux at 4.42 AE. The age of these strongly calcic plagioclase clasts, believed to be remnants of the anorthositic lunar crust, establishes a lower age limit to the end of the early lunar differentiation and thus places a strong constraint to the lunar evolution.     

Richardson's number in the free atmosphere

Summary From an example of high-resolution FPS-16 wind measurements in the free atmosphere it is shown that Richardson's number is strongly dependent on the scale of the layer over which it is measured. This may be one of the reasons for the discrepant results obtained by various authors in correlating the occurrence of clear-air turbulence with this number.

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Zusammenfassung An Hand eines Beispiels detaillierter FPS-16 Windmessungen in der freien Atmosphäre wird gezeigt, daß die Richardsonsche Zahl wesentlich von der Größenordnung der Schichtdicke abhängt, über welche sie gemessen wird. Dies mag einer der Gründe dafür sein, daß die Versuche verschiedener Autoren, diese Zahl mit dem Auftreten von clear-air turbulence (Flugturbulenz im wolkenfreien Raum) zu korrelieren, zu widerspruchsvollen Ergebnissen führten.

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Résumé Sur la base d'un exemple de mesure détaillée du vent en atmosphère libre au moyen d'un système FPS-16, on peut démontrer que le nombre deRichardson dépend en grande partie de l'orde de grandeur de l'épaisseur de la couche au-dessus de laquelle il est mesuré. Ceci est une des raisons pour lesquelles les essais de différents auteurs qui recherchent la corrélation entre ce nombre et la turbulence en atmosphère claire (clear-air turbulence) conduisent à des résultats contradictoires.

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With 3 Figures