On the influence of non-Gaussianity on turbulent transport

Non-Gaussianity effects, first of all the influence of the third and fourth moments of the velocity probability density function, have to be assessed for higher-order closure models of turbulence and Lagrangian modelling of turbulent dispersion in complex flows. Whereas the role and the effects of the third moments are relatively well understood as essential for the explanation of specific observed features of the fully developed convective boundary layer, there are indications that the fourth moments may also be important, but little is known about these moments. Therefore, the effects of non-Gaussianity are considered for the turbulent motion of particles in non-neutral flows without fully developed convection, where the influence of the fourth moments may be expected to be particularly essential. The transport properties of these flows can be characterized by a diffusion coefficient which reflects these effects. It is shown, for different vertical velocity distributions, that the intensity of turbulent transport may be enhanced remarkably by non-Gaussianity. The diffusion coefficient is given as a modification of the Gaussian diffusivity, and this modifying factor is found to be determined to a very good approximation by the normalized fourth moment of the vertical velocity distribution function. This provides better insight into the effect of fourth moments and explains the varying importance of third and fourth moments in different flows.     

Water Budgets of Two Watersheds in Different Climatic Zones under Projected Climate Warming

A deterministic monthly runoff model (MINRUN96)was applied to watersheds with substantially differentclimates. One watershed is in the north-central U.S.(Minnesota) and is heavily timbered. The other is inthe south-central U.S. (Oklahoma) and is mainlycovered with pastures and agricultural crops. Runoffwas simulated for past historical climate and twoprojected 2 × CO₂ climate scenarios. The output ofGeneral Circulation Models (GCMs) was used to specifythe two 2 × CO₂ climate scenarios. One GCM is theGoddard Institute of Space Studies (GISS) model andthe other is from the Canadian Center of ClimateModelling (CCC). In the northern watershed morerunoff is projected to occur in winter under a warmerclimate and less runoff in spring. About 80%increase in fall runoff and 20% decrease in soilmoisture in June and July is projected for thesouthern watershed. When runoff simulations for the2 × CO₂ climate scenarios were compared to pastrunoff, it was apparent that the change in runoffdepended on both the season and the magnitude of theprecipitation change. An increase in springprecipitation caused a significant increase in directrunoff, whereas an increase in fall precipitationcaused only a slight increase in total runoff. Alsothe runoff-precipitation relationship in the warm andseasonally dry southern watershed is very differentfrom that in the temperate and humid climate of thenorth. Therefore, runoff responses to projectedclimate change are substantially different in the tworegions.     

Subglacial topography and internal structure of central and western Dronning Maud Land, Antarctica, determined from airborne radio echo sounding

During five austral summers, from 1994/1995 until 1998/1999, the Alfred Wegener Institute (AWI) carried out a large airborne radio echo sounding (RES) survey in Dronning Maud Land (DML), Antarctica. These ice thickness measurements are part of the AWI contribution to the pre-site survey for a deep ice core drill site in DML within the European Project for Ice Coring in Antarctica (EPICA). The survey encompasses more than 90,000 km of RES profiles over DML and the adjacent coastal area, covering more than 1 million km². The lower boundary of the ice sheet could be determined area-wide. Internal horizons occurring in the upper two-thirds of the ice column can also be traced for several hundred kilometers. This work presents the latest maps of the subglacial topography of the investigated area as well as of an internal horizon.     

Boundary layer structure over an inhomogeneous surface: Simulation with a non-hydrostatic mesoscale model

A three-dimensional, non-hydrostatic mesoscale model is used to study boundary-layer structure over an area characterized by the city of Copenhagen, the Øresund strait, and adjacent coastal farmland. Simulations are compared with data obtained on June 5, 1984 during the Øresund experiment.Under moderately strong wind conditions, a stable internal boundary layer (IBL) developed over the Øresund strait during the day. Near-surface winds decelerate over water due to diminished vertical momentum transfer.The turbulent kinetic energy field closely reflects the surface roughness distribution due to the imposed relatively strong wind forcing. TKE budgets over water, farmland and a city area are discussed by inspection of vertical profiles of the individual terms. The buoyancy term is used to indicate IBL heights because it changes sign at the boundary between different stability regimes. Measured and simulated dissipation rates show a decrease in the transition zone as the air travels over water and an abrupt increase when the IBL over a downwind city area is intersected. The top of the stable IBL is characterized by a minimum in the vertical TKE profile.     

Die Untersuchung ortsabhängiger Variablen: Modelle,Methoden und Probleme

Zusammenfassung Als ortsabhängige Variable wird jede räumlich verteilte numerische Funktion bezeichnet, deren von Ort zu Ort scheinbar kontinuierliche Veränderung durch einfache Funktionen nicht dargestellt werden kann. Entsprechende Variablen sind in geowissenschaftlichen Problemen häufig anzutreffen: Geochemische und geophysikalische Daten, Erzgehalte, strukturelle Angaben, wie die Höhenlagen von Schichtgrenzen etc.Um zuverlässige Aussagen zu erhalten, sind bei der Untersuchung ortsabhängiger Variablen, wie auch bei der Erstellung von Isoplethen-Karten, verschiedene Einflußgrößen zu berücksichtigen: Die räumliche Verteilung der Datenpunkte, Existenz von Trends, Autokorrelation und Heteroskedastizität sind Eigenschaften, denen durch die Wahl eines geeigneten Modells bzw. einer sinnvollen Auswertungsmethode Rechnung getragen werden sollte.Folgende Verfahren werden kurz beschrieben und einander hinsichtlich ihrer Einsatzmöglichkeiten und der Zuverlässigkeit ihrer Resultate insbesondere für Probleme der Erzvorrats-Berechnung kritisch gegenüber gestellt:Interpolations-Verfahren, Trendflächen-Analysen, Krigeage.

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A regionalized variable is any numerical function with a spatial distribution which varies from one place to another with apparent continuity, but the change of which cannot be represented by any workable function. This definition characterizes many variables in geosciences as chemical, geophysical and structural data, ore contents etc.To get reliable results in the analysis and display of regionalized variables (estimation of ore reserves, automatic conturing etc.) it is necessary to consider the following quantities: distribution and heteroscedasticity of data, existence of global and local trends, autocorrelation. According to these facts a mathematical model must be chosen to describe the data as well as an adéquat method to display the results. The paper gives a short survey about some problems connected with the application of trend analysis, inaterpolation methods and kriging. The reliability of the results are compared with respect to ore estimation and graphical display.

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Résumé La notion de variable régionalisée sert à définir les fonctions de l'espace dont la valeur varie d'un lieu à un autre avec une certaine apparence de continuité, sans qu'il soit en général possible d'en représenter la variation par une loi mathématique extrapolable. En sciences de la terre on peut citer par example des analyses géochimiques, géomagnétiques, minières ou structurales comme l'altitude d'une région.La fiabilité des résultats obtenus par les traitements dépend des influences différentes: La distribution des données dans l'espace, l'existence de tendances, l'autocorrélation etc., Nous présentons les méthodes les plus importantes pour comparer leur mise en pratique, particulièrement en géologie minière: Méthodes d'interpolation, analyses des surfaces de tendance, krigeage.

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Die Bedeutung der Strömung als ökologischer Faktor

Ohne Zusammenfassung     

Die Granulite der südlichen Böhmischen Masse

Zusammenfassung Die Granulite von Pöchlarn und Wieselburg und des Dunkelsteiner Waldes (Niederösterreich) wurden neu kartiert. Danach gliedert die Diendorfer Störung, eine große Blattverschiebung, den früher einheitlichen Granulitkörper in zwei Teile. Mineralogische und chemische Untersuchungen ergaben, daß verschiedenartige Sedimente mit Tuffeinlagerungen und saure Magmatite die Ausgangsgesteine waren. Die Granulite stellen einen älteren Metamorphosezyklus als die umgebenden Gesteine dar.

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The granulites of Pöchlarn-Wieselburg and of the Dunkelsteiner Wald (Niederösterreich) were mapped again. Thereafter the Diendorf fault, a great wrench fault, divides the formerly coherent granulite body into two parts. Mineralogical and chemical analyses proved that different sediments with intercalated tuffs and acid igneous rocks have been the primary rocks. The granulites represent an older metamorphic cycle than the country rocks.

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Résumé Les granulites de Pöchlarn-Wieselburg et du Dunkelsteiner Wald ont été cartographiées. On a constaté que l'accident de Diendorf est une grande faille verticale de décrochement, partageant la masse des granulites en deux parties. Des analyses minéralogiques et chimiques ont montré que les roches primaires étaient des sédiments divers avec des couches intercalées de tuf et de roches acides ignées. Les granulites representent un cycle métamorphique qui est plus vieux que les roches encaissantes.

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The Precambrian geology of the “Borborema”-Belt (States of Paraíba and Rio Grande do Norte; northeastern Brazil) and the origin of its mineral provinces

In the crystalline area of the “Borborema” in NE Brazil the final geologic event was a strong static recrystallization, which is manifest in regional granitization, hybride granite, or pegmatite veins. The manifestation varies within the mapped area, it depends on lithology, thickness and structure of the Precambrian metasediments. The age of this phase is between 550 and 450 M. years. Recrystallization is accompanied by weak folding of pre-existing anticlines as indicated by the structural control of the Borborema pegmatites. The principal phase of deformation and the accompanying regional metamorphism are considered to be older, approximately 850 M. years or more. This older regional metamorphism produced rocks of the almandine-staurolite subfacies of the amphibolite facies; locally higher (cordierite and sillimanite subfacies) or lower (greenschist facies) degree of metamorphism occurs. The pyroxene-hornfels facies, which is found in the contact aureoles of hybride granites, occurs exclusively in the tactites (metamorphic dolomitic marls). In clastic metasediments, high grade metamorphic facies is restricted to the contact aureole of a small hypersthene diorite stock. The structure is simple, and consists of synclines and anticlines the axial planes of which are vertical or, rarely, inclined. Faults are rare. The degree of lateral compression varies: low in the NW part of the area mapped, intermediate in die NE, and high in the southern part. The southern part belongs to the “Paraíba Transversal Zone”, an E-W striking fault zone along which the northern parts have been dislocated horizontally to the East. Stratigraphically the sequence is subdivided into three major groups by unconformities, which, however, are masked intensely by the principal tectonic events. These groups are: The oldest member occurs but locally in the cores of some anticlines; the youngest constitutes the cores of most synclines. The Caicó can be subdivided, in the most part, as follows: Florânia and Parelhas are essentially composed by unsorted clastic sediments (graywackes and arcoses). The Equador is a local lithofacies of the latter restricted to one anticline and a small part of another, and composed of well sorted clastics (muscovite quartzite). Another quartzite, locally developed at the top of the Florânia in the western part of the area, has been named “Member S. José do Seridó”. The Quixaba contains essentially carbonate rocks, but with intercalations of clastic sediments. The scheelite province of the area is generally connected with the Quixaba-Formation, the marbles of which served as transportation channels, whereas tactites were the receptors of the ore-bringing solutions, derived from some palingenetic granites and thus, indirectly, from the metasediments of the Parelhas. The deposition does not belong to the principal phase of contact metamorphism, but to a later-phase with hydrothermal paragenesis. Scheelite occurs also in common quartz-albite-veins. The famous pegmatite-province (Ta, Nb, Li, Be) cannot be considered as a product of magmatic differentiation, either. It must be the product of the statical recrystallization of the muscovite-rich Equador quartzite, by addition of thermal energy and K-rich solutions from the depth. Thus this province is only a special case of the general “granitization” with K-metasomatism: $$Quartz + Muscovite + K^ + \to Microclin + H^ + + Water.$$ The resulting fluids formed pegmatites in the rocks overlying the quartzite, i. e., generally in the micaschists of the Seridó-Group. Productive dykes always fill longitudinal or transversal tension cracks. The Borborema province of zoned pegmatites is thus an excellent example for the recent genetic hypothesis ofGresens, all requirements of it being fulfilled.     

Analyse der Bewegungen an der Umbiegung der „Peridriatischen Naht“ (Insubrische Linie/Pusterer Linie) in der Umgebung von Mauls (Südtirol)

Zusammenfassung Untersuchungen der magnetischen Suszeptibilitätsanisotropie an der Judikarien/Pusterer-Linie ergaben, daß an der Judikarien Linie und an der östlichen Pusterer Linie kompressionelle Vorgänge nachweisbar sind. Im W-Teil der Pusterer Linie (E Mauls) war die Kompression wesentlich schwächer. Diese Ergebnisse werden mit einer Bewegungsanalyse in Zusammenhang gebracht, die auf plattentektonischen Modellen, die diesen Raum betreffen, beruht. Demnach ist eine Gegenuhrzeigersinnrotation einer Platte, die die Periadriatische Naht beinhaltet, mit anschließender Kollision mit der Briançonischen Platte (Frisch 1977) für die Aktivierung (oder Reaktivierung) verantwortlich. Die gesamte Energie dieser Vorgänge entlädt sich an der Judikarien Linie und der östlichen Pusterer Linie.Schlüsselwörter: Suszeptibilitätsanisotropie; Magnetic Fabric; Brixener Granit; ostalpines Altkristallin; Periadriatische Naht; Plattentektonik.

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Magnetic fabric analyses on samples from the junction of the Pusterer Line with the Judicarian Line in South Tyrol have been carried out to determine a model for the compressions, movements and dynamics of the Periadriatic Line (P. L.). The results have been incorporated into a plate-tectonic model whereby the P. L. was activated (or reactivated) by a collision of a plate containing the P. L. against the Briançonic Platform (Frisch 1977). The energy of the collision appears to have been dissipated in compression along the Judicarian Line and movement along the Pusterer Line.

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Résumé Les analyses de texture d'échantillons magnétiques à la jonction de la ligne Judicarienne avec la ligne de Pusterer prouvent que sur la ligne Judicarienne et sur la ligne Est de Pusterer des phénomènes de compression sont démonstrables. Dans la partie Ouest de la ligne de Pusterer (E Mauls), la compression était considérablement plus faible. Ces résultats sont mis en relation avec une analyse de mouvements qui repose sur des modèles de plaques tectoniques qui concernent cet espace. Par conséquent, une rotation dans le sens inverse de l'aiguille d'une montre d'une plaque qui comporte la ligne Périadriatique et qui a une collision reliée à la plaque briançonique est responsable de l'activation (ou de la réactivation), (Frisch, 1977).Toute l'énergie de ces phénomènes se décharge sur la ligne Judicarienne et sur la ligne Est de Pusterer.

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