Dünung und Windstau

Summary These remarks trie to explain the behaviour of local wind effect on the coast under the additional influence of swell approximately running parallel to the wind's direction. Owing to the high speed of long swell waves the wind's tangential shearing strain on the water masses may become less effective than it would do if no coincidence with swell waves would occur.

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La houle et l'effet local du vent

Résumé Cet essai cherche à expliquer le comportement de l'effet local du vent sous l'influence additionnelle d'une houle qui suit approximativement la direction du vent. Par suite de la grande vitesse de propagation d'une longue houle, l'effet de cisaillement tangentiel que le vent exerce sur l'eau diminuera dans le cas où l'effet local du vent coincide avec le phénomène additionnel de la houle.

     

Über die DÜnung aus einem Windfeld,welches am Beobachtungsort in einiger Entfernung vorbeizieht

Zusammenfassung Es werden die zum Teil recht verwickelten Bedingungen besprochen, denen eine am festen BeobachtungsortA auftretende DÜnung genÜgt, wenn das wellenerzeugende Windfeld sich dem PunktA wohl nähert, an ihm dann aber in einiger Entfernung vorbeizieht. Es werden getrennt behandelt: 1. wandernde Windfelder, welche seit langer Zeit eine ausgereifte Windsee besitzen, 2. wandernde Windfelder, deren Ausbildung erst kÜrzere Zeit zurÜckliegt.An geeigneter Stelle wird ein Diagramm gegeben, welches die Bestimmung der angular spreading factors (W. J. Pierson jun., G. Neumann und R. W. James [1953]) wesentlich erleichtert.Abschließend wird die Frage erörtert, ob ein Punkt am Rande des Windfeldes den gesamten Windfeld-Leerand ausreichend repräsentieren kann.

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On swell generated by a fetch passing at some distance from the observation point

Summary The paper treats the rather complex conditions that may lead to the occurrence of swell at a fixed observation pointA when the wave generating fetch though approaching pointA passes it at some distance. Two contingencies are separately discussed: 1) moving fetches associated for a long time past with a fully developed wind sea, 2) moving fetches whose generation took place only quite recently.The paper includes a diagram which largely facilitates the determination of the angular spreading factor (W. J. Pierson jun., G. Neumann, and R. W. James [1953]).In the end, the question is discussed whether one point on the border of the fetch may be regarded as being sufficiently representative of the entire lee-side of the fetch.

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Sur une houle soulevée par un »fetch« qui passe le point d'observation à quelque distance

Résumé Ce travail traite les conditions assez complexes qui peuvent conduire à l'apparition de houles à un point fixe d'observationA si le »fetch« qui a soulevé les vagues en question s'approche de ce point mais finit par le passer à quelque distance. On discute deux éventualités: 1) des »fetches« progressifs dont les vagues de vent on depuis longtemps terminé leur developpement, 2) des »fetches« progressifs qui n'ont accompli leur formation que depuis peu.On a introduit dans le travail un diagramme qui rend beaucoup plus facile la détermination des facteurs d'extension angulaire (»angular spreading factors«) (W. J. Pierson, jun., G. Neumann et R. W. James [1953]).Enfin, on discute la question si un seul point sur le bord du »fetch« peut suffisamment représenter les conditions dominant sur tout le bord sous le vent.

     

Ergebnisse von Messungen heutiger Krustenbewegungen

Ohne Zusammenfassung     

Daily Weather Observations in Sixteenth-Century Europe

Thirty-two weather diaries written in astronomical calendars in central Europe in the late fifteenth and sixteenth centuries are presented and discussed. Systematic weather observations were promoted by the rise of planetary astronomy and its application in astro-meteorology. The practice of keeping weather diaries spread from Cracow (Poland) to Ingolstadt (Germany) and from there to other universities. The data obtained from these sources provided the backbone for setting up series of precipitation indices for Poland, Germany and Switzerland. Monthly statistics of days with precipitation, snowfall and frost were computed by counting the relevant entries in the most important diaries. The results were compared with either those obtained from instrumental measurements in the same place or with those from modern instrumental measurements in a neighbouring place. The final results show that autumn was considerably colder in the early sixteenth century. April was considerably drier and July was wetter during the period 1508-1531 than during 1901-1960. In order to highlight the impact of weather patterns on grain prices in a year of crisis, the timing of wet and dry spells in southern Poland and southern Germany is compared for the year 1529. Winters became 1.7°C colder from 1564 to 1576 and the month of July tended to be wetter than in 1901-1960. Details noted in the diaries kept between 1585 and 1600 by the astronomers Brahe (near Copenhagen) and Fabricius (in the Ostfriesland region of northwestern Germany) closely agree. It rained more often in June and July and temperatures dropped. The winter months were more frequently dominated by winds from easterly directions, the frequency of snowfall was higher and a deficit occurred in precipitation. This points to a higher frequency of high pressure in the Fennoscandian area with cold air advection from the east or northeast.     

Geology, geochemistry and petrogenesis of intrusive rocks of the Wallagga area, western Ethiopia

Crystalline rocks from the western Ethiopian Precambrian terrain comprise two major rock groups: (1) the often migmatised eastern and western high-grade gneisses; and (2) the central low-grade metavolcanosedimentary rocks. Granitoid bodies of different ages and compositions intrude these rocks. Field observations, petrographic investigations, and geochemical features support a two-fold classification of the granitoid rocks. The volcanic arc granitoids (VAG) are most common and include the Ujjukka granite and granodiorite, and the Dhagaa Booqa and Guttin K-feldspar megacrystic granites. The second and geographically more restricted group represents within-plate or anorogenic (A-type) granitoids, typified by the Tullu Kapii syenite. Geochemically, the Tullu Kapii syenite is characterised by moderate to high contents of SiO₂, total alkalis, Y, Nb, Ta, Hf, Zn, Zr, Ga, ΣREE, higher ratios of Fe₂O_3(total)/MgO, , , and lower contents of CaO, MgO, Sr, and Ba, compared to the other granitoids. The VAG group shows chondrite-normalised REE patterns with slightly enriched LREE and flat HREE patterns without significant Eu anomalies. In contrast, the Tullu Kapii A-type granitoid is characterised by a nearly horizontal REE pattern with variable negative Eu anomalies. The Ujjukka granite and granodiorite; and the Dhagaa Booqa and Guttin K-feldspar megacrystic granites originated in a two-step process, which involves batch equilibrium melting of basaltic or andesitic material producing tonalitic magma, followed by fractional crystallisation. The Tullu Kapii syenite was the product of partial melting of source rocks enriched in high field strength elements.     

Effects of groundwater flow on mineral diagenesis, with emphasis on carbonate aquifers

 This article provides a critical synopsis of the effects of groundwater flow on mineral diagenesis. Emphasis is placed on those aspects and processes that change porosity and permeability in carbonate aquifers, because they are of particular importance to human societies as sources of supplies of water for human consumption (drinking, irrigation) and of crude oil and natural gas. Diagenetic settings in carbonates as well as clastics are generally ill defined. This paper proposes a new comprehensive classification of diagenetic settings into near-surface, shallow-, intermediate-, and deep-burial diagenetic settings; hydrocarbon-contaminated plumes; and fractures. These settings are defined on the basis of mineralogy, petroleum, hydrogeochemistry, and hydrogeology. This classification is applicable to all sedimentary basins. Diagenesis is governed by various intrinsic and extrinsic factors that include thermodynamic and kinetic constraints, as well as microstructural factors that may override the others. These factors govern diagenetic processes, such as dissolution, compaction, recrystallization, replacement, and sulfate–hydrocarbon redox-reactions. Processes such as cementation, dissolution, and dolomitization require significant flow of groundwater driven by an externally imposed hydraulic gradient. Other processes, such as stylolitization and thermochemical sulfate reduction, commonly take place without significant groundwater flow in hydrologically nearly or completely stagnant systems that are geochemically "closed." Two major effects of groundwater flow on mineral diagenesis are enhancement and reduction of porosity and permeability, although groundwater flow can also leave these rock properties essentially unchanged. In extreme cases, an aquifer or hydrocarbon reservoir rock can have highly enhanced porosity and permeability due to extensive mineral dissolution, or it can be plugged up due to extensive mineral precipitation. Received, April 1998 · Revised, July 1998 · Accepted, September 1998     

Nonlinear wave coupling in type IV solar radio bursts

In order to explain a fine structure of parallel ridges in stationary type IV continua, the emission due to the coupling of electrostatic upper hybrid waves and Bernstein waves at the sum frequency of the upper hybrid and harmonics of the gyro frequency has been calculated. If the energy density of these electrostatic waves is of the order of 10^-3 times the thermal energy density, then the observed zebra pattern can be emitted by a region with a diameter of 10³ km.     

The period of rotation and the photoelectric lightcurve of the minor planet 79 eurynome

The minor planet 79 Eurynome was observed during the 1974 opposition for four nights in November, using a photoelectric photometer attached to the 60 cm telescope at the Observatoire de Haute Provence, France. A synodic period of P_syn = 5^h 58^m46^s ± 6^s m.e. was derived. The total amplitude of the lightcurve is only 0.05 mag. The lightcurve shows a double maximum and double minimum. Both minima appear to be at the same level. Observations were carried out in an instrumental filter system (UBV)' Results are shown only for V′, but U′ and B′ measurements supplement the conclusions concerning the rotation. The phase angle α, covered by the observations, ranges from 3 to 5°. The present results for 79 Eurynome rule out the longer period of 0^d.49830 derived by F. Scaltriti and V. Zappalà in favor of their possible period of 0^d.24915.     

Hill stability and distance curves for the general three-body problem

The notion of Hill stability is extended from the circular restricted 3-body problem to the general three-body problem; it is even extended to systems of positive energy and the Hill's curves with their corresponding forbidden zones are generalized.Hill stable systems of negative energy present a hierarchy: they have a close binary that can be neither approached nor disrupted by the third body. This phenomenon becomes particularly clear with the distance curves presentation.The three limiting cases, restricted, planetary and lunar are analysed as well as some real stellar cases.     

A candidate of the Induan-Olenekian boundary stratotype in the Tethyan region

The Olenekian Stage was proposed by Kiparisova and Popov[1] based on the type section along the lower reaches of the Olenek River, Siberia. Later research showed that this section con-tains only the Olenikites spiniplicatus Zone of the Upper Olenekian Sta…