Numerical properties of low-frequency expansions for the reflection and transmission coefficients from transition layers

Summary The numerical properties of the low-frequency expansions for the reflection and transmission coefficients of SH-waves from transition layers, derived in [1], are studied. It is shown that the expansions are suitable for computations only when the thickness d of the transition layer is small in comparison with the wavelength of the incident wave (d0.5). For thicker transition layers, certain modifications of the method are suggested.     

A combined geophysical model of the crust for the south of the European part of the USSR

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Presented at the KAPG Symposium Problems of Interpretation and Construction of Physical Models of Litosphere, Liblice (CSSR), March 6–10, 1978.     

On forecasting of cyclogenesis in the West Mediterranean and other areas bounded by mountain ranges by baroclinic model

Summary Changes occurring in the thermal structure of air masses in the Alps area and the West Mediterranean region, during cyclonic developments in the Gulf of Genoa, have been considered. The effect of the height and the form of the mountain ranges as well as that of the nonadiabatic processes, on the deformation of the thickness pattern, have been discussed. These factors have been further taken into consideration for a modification of the equations used inEstoque's method for the baroclinic model, and a new method has been developed for forecasting cyclogenesis in regions bounded by mountain ranges.

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Zusasmmenfassung Es werden die Änderungen der thermischen Struktur der Luftmassen im Alpengebiet und im westlichen Mittelmeerraum bei der Entwicklung von Zyklonen im Golf von Genua aufgezeigt und die Einflüsse von Höhe und Form der Gebirgszüge sowie von nichtadiabatischen Vorgängen auf die Deformation der relativen Topographie besprochen. Diese Faktoren werden auch zur Modifikation der in der Methode vonEstoque für ein baroklines Modell verwendeten Gleichungen in Betracht gezogen und damit wird eine neue Methode zur Vorhersage der Zyklogenese unter dem Einfluß von Gebirgszügen entwickelt.

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Résumé On expose dans ce mémoire à quelles modifications la structure thermique des masses d'air est soumise dans la région des Alpes et dans le bassin occidental de la Méditerranée lors du développement de dépressions sur le Golfe de Gênes. On y discute en outre l'influence de la hauteur et de la forme des chaînes de montagnes ainsi que celle des processus non-adiabatiques sur des déformations de la topographie relative. Tous ces éléments sont pris en considération pour leur adapter les équations utilisées dans le modèle baroclined'Estoque. Par là, on accède à une nouvelle méthode de prévision de la cyclogénèse, méthode qui tient compte de l'influence des chaînes de montagnes.

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With 5 Figures     

Zur Revision der GattungGloeocapsa Kützing (Cyanophyta)

Ohne Zusammenfassung Die vorliegende Arbeit entstand dank der Unterstützung der Alexander-von-Humboldt-Stiftung, Bad Godesberg.     

Rain rate estimation from a synergetic use of SSM/I, AVHRR and meso-scale numerical model data

Summary In this paper a retrieval technique for estimating rainfall rates is introduced. The novel feature of this technique is the combination of two satellite radiometers — the Special Sensor Microwave/Imager (SSM/I) and the Advanced Very High-Resolution Radiometer (AVHRR) — with mesoscale weather prediction model data. This offers an adjustment of the model atmospheres to reality which is necessary for calculating brightness temperatures that can be compared with microwave satellite measurements.In sensitivity studies it was found that the estimation of precipitation is determined to a high degree by the particle size distribution of rain and snow, especially by the size distribution of solid hydrometeors. These studies also reveal the influence of the knowledge of the correct cloud coverage inside a SSM/I pixel and the importance of using a realistic temperature profile instead of using standard atmospheres.The retrieval technique is based on radiative transfer calculations using the model of Kummerow et al. (1989). The algorithm consists of two parts: First Guess (FG) brightness temperatures for the SSM/I frequencies are generated as a function of the cloud top height and the cloud coverage, derived from AVHRR data and predictions from a meso-scale model. The rainfall rate of different types of clouds containing raindrops, ice particles and coexisting ice and water hydrometeors is then calculated as a function of the cloud top height. As an example, a strong convective rain event over the western part of Europe and over the Alps is taken to evaluate the performance of this technique. Good agreement with radar data from the German Weather Service was achieved. Compared to statistical rainfall algorithms, the current algorithm shows a better performance of detecting rainfall areas.With 12 Figures     

Propagation of the Rossby waves on two dimensional rectangular grids

Summary A simple two-dimensional quasi-geostrophic linearized model of the atmosphere is used to investigate the behaviour of the quasi-geostrophic modes for five horizontal rectangular grids. Numerical expressions for frequencies of Rossby waves for all grids are evaluated. It was found that the B and C grids produce only negative frequencies as well as the continuous case. The D grid has negative and zero frequencies. Finally, it was found that the A and E grids produce positive frequencies and eastward moving Rossby waves.With 2 Figures     

Weak Contrast PP Wave Displacement R/T Coefficients in Weakly Anisotropic Elastic Media

—Approximate PP plane wave displacement coefficients of reflection and transmission for weak contrast interfaces separating weakly but arbitrarily anisotropic elastic media are presented. The PP reflection coefficient for such an interface has been derived recently by Vavry?uk and P?en?ík (1997). The PP transmission coefficient presented in this paper was derived by the same approach. The coefficients are given as a sum of the coefficient for the weak contrast interface separating two nearby isotropic media and a term depending linearly on contrasts of the so-called weak anisotropy (WA) parameters (parameters specifying deviation of properties of the medium from isotropy), across the interface. While the reflection coefficient depends only on 8 of the complete set of the WA parameters describing P-wave phase velocity in weakly anisotropic media, the transmission coefficient depends on their complete set. The PP reflection coefficient depends on "shear-wave splitting parameter" γ. Tests of accuracy of the approximate formulae are presented on several models.     

Some foundation stability problems of the railway bridge over the Mala Rijeka

SummarySome Foundation Stability Problems of the Railway Bridge over the Mala Rijeka The authors presented an outlay of problems occurring in estimating the stability of rocky slopes loaded by large vertical forces. General attitudes, kept by the authors during the stability analysis for an actual case — foundation of piers No. 3 and 4 of the railway bridge across the Mala Rijeka, are also presented. The results of calculation as well as the advantages of the approach applied are outlined in the paper. Finally, general conclusions are drawn regarding the method to be kept in solving the stability of slopes loaded by large artificial loading.With 7 Figures     

New Definition of Discovery for Solar System Objects

We propose a new formal definition of discovery for a Solar System object. It is based on an objective and mathematically rigorous algorithm to assess when a set of observations is enough to constitute a discovery. When this definition is satisfied, in almost all cases the orbit is defined well enough to establish the nature of the object discovered (Main Belt vs. Near Earth Asteroid, Trans-Neptunian vs. long period comet). The frequency of occurrence of exceptions is estimated by a set of numerical experiments. The availability of a non-subjective definition of discovery allows some rules to be adopted for the assignment of discovery credit with a minimum risk of dispute. Such rules should be fair, encourage good practice by the observers and acknowledge the contribution of the orbit computers providing the identifications and the orbits, as well as the one of all the contributing observers.     

Quality control and homogeneity of Turkish precipitation data

Outlier trimming and homogeneity checking/correction were performed on the monthly precipitation time series of various lengths from 267 stations in Turkey. Outlier values are usually found during dry summer months, and are concentrated mostly over the southern parts of the country, where the dry period is most pronounced, implying natural extremes rather than wrong measurements. Homogeneity analysis was done using the Standard Normal Homogeneity Test, on an individual monthly basis, which led to many non‐testable series due to lack of reference stations, especially during summer months. Yet, remaining testable months were usually helpful for the assessment of homogenity, revealing a well distributed set of stations that proved to be homogeneous. There were still a number of stations which either could not be tested efficiently, or were classified as inhomogeneous. Lack of metadata is argued to be largely responsible for inefficient homogeneity testing. Copyright © 2008 John Wiley & Sons, Ltd.