On characterizing the temporal dominance patterns of model parameters and processes

Diagnostic analyses of hydrological models intend to improve the understanding of how processes and their dynamics are represented in models. Temporal patterns of parameter dominance could be precisely characterized with a temporally resolved parameter sensitivity analysis. In this way, the discharge conditions are characterized, that lead to a parameter dominance in the model. To achieve this, the analysis of temporal dynamics in parameter sensitivity is enhanced by including additional information in a three‐tiered framework on different aggregation levels. Firstly, temporal dynamics of parameter sensitivity provide daily time series of their sensitivities to detect variations in the dominance of model parameters. Secondly, the daily sensitivities are related to the flow duration curve (FDC) to emphasize high sensitivities of model parameters in relation to specific discharge magnitudes. Thirdly, parameter sensitivities are monthly averaged separately for five segments of the FDC to detect typical patterns of parameter dominances for different discharge magnitudes. The three methodical steps are applied on two contrasting catchments (upland and lowland catchment) to demonstrate how the temporal patterns of parameter dynamics represent different hydrological regimes. The discharge dynamic in the lowland catchment is controlled by groundwater parameters for all discharge magnitudes. In contrast, different processes are relevant in the upland catchment, because the dominances of parameters from fast and slow runoff components in the upland catchment are changing over the year for the different discharge magnitudes. The joined interpretation of these three diagnostic steps provides deeper insights of how model parameters represent hydrological dynamics in models for different discharge magnitudes. Thus, this diagnostic framework leads to a better characterization of model parameters and their temporal dynamics and helps to understand the process behaviour in hydrological models. Copyright © 2015 John Wiley & Sons, Ltd.     

Spalling Experiments on Large Hard Rock Specimens

Specimens of coarse-grained Äspö diorite were axially compressed to observe stress-induced spalling. The specimens had a novel design characterized by two manufactured large radius notches on opposite sides. The tangential stress occurring in the notches aimed to represent the tangential loading around a circular opening. Fracture stages were monitored by acoustic emission measurements. Rock chips were formed similar to those found in situ, which indicates a similar fracture process. Slabs were cut out from the specimens and impregnated using a fluorescent material to visualize the cracks. The cracks were subsequently examined by the naked eye and by means of microscopy images, from which fracture paths could be identified and related to different minerals and their crystallographic orientations. The microscopy analyses showed how the stress field and the microstructure interact. Parallel cracks were formed 2–4 mm below the surface, sub-parallel to the direction of the maximum principal stress. The crack initiation, the roles of minerals such as feldspar, biotite and quartz and their grain boundaries and crystallographic directions are thoroughly studied and discussed in this paper. Scale effects, which relate to the stress gradient and microstructure, are discussed.     

Effects of water on strength and failure mode of coarse-grained granites at 300°C

Summary Deformation experiments have been performed in a triaxial compression cell at a temperature of 300°C and confining pressures up to 65 MPa using samples of homogeneous, fresh two-mica-granite (RM) and monzogranite (CM). The cylindrical specimens (d=70 mm, h=140 mm, V=540 cm³) were tested undrained under dry (105°C), as received, and water saturated conditions at deformation rates between and . The mechanical behaviour of the two types of coarse-grained, crystalloblastic granites is critically influenced by mineralogical composition, porosity, and the amount of intergranular water present in the samples. The failure stress of the CM granite is at about 65% of that of the RM granite; in both rocks strength decreases with increasing porosity and water content.The presence of interstitial water causes a failure mode of non-localized, homogeneously distributed microcracking in the central parts of the samples, whereas, in runs with dry granites, strain localization along a single shear fracture was observed. When aqueous fluids are present, the macroscopic style of deformation of granites appears to be ductile even at lowP andT conditions. Strength and angle of internal friction are reduced to very low values. The style of deformation, as well as the reduction of strength of the water-saturated rock samples, is due to mechanical and chemical effects of intergranular water at elevated temperatures.The maximum differential stresses measured for these coarse-grained granites are much lower than the strength commonly reported for other granites, e. g. Westerly and Charcoal granites. Our data suggest that the strength of the granitic crust under differential stress is lower than currently deduced from laboratory experiments.     

Volcanic hazards in the surroundings of Pico de Orizaba,eastern Mexico

Volcanic hazards from Pico de Orizaba volcano are presented here tor the first time. Some 1.3 million people live within the hazard zone, which in the most severe case would encompass the Mexican Gulf coast, east of the volcano. Three major cities located in the eastern part of the hazard zone account for 800 000 of this population and about 200 000 people live within a 20 km radius of the volcano. Probability calculations are presented as an attempt to quantify the hazards in the surroundings of the volcano. Such quantification can be of use in planning for future land use within the hazard zones.A zone of about 10 km radius centred on the top crater is a high hazard zone for gravity-driven flows and fallout ejecta. For large volume eruptions, the radius could be extended to 120 km to the east and 60 km to the west. The asymmetrical distribution is related to the topography of the volcano. Hazards from Pyroclastic-fall deposits are principally to the west of the volcano, since easterly winds are dominant in the area lava-flow hazards are greatest within a 10 km radius from the summit crater. Pyroclastic flow hazards are high up to 20 km from the volcano summit.In the case of reactivation of the volcano, melting of a glacier covering the summit of Pico de Orizaba having a volume equivalent to some 45 × 10⁹ litres of water, would produce lahars which would descend the flanks of the volcano.     

Drag force on a circular cylinder in unseparated laminar high Reynolds number nonlinear random oscillatory flow

The stochastic properties of the drag force maxima on a circular cylinder subjected to nonlinear random waves are investigated. Unseparated laminar high Reynolds number flow is considered. A simplified approach based on second order Stokes waves is presented, including the sum-frequency effect only. It is demonstrated how a drag force formula valid for regular linear waves can be used to find the cumulative distribution function of individual drag force maxima for nonlinear irregular waves. Here the [Wang, 1968] drag force coefficient is used.     

Variations in heavy metals concentrations in Antarctic snows from 1940 to 1980

Concentrations of Pb, Cd, Cu and Zn have been measured using improved ultraclean procedures in a succession of twenty six snow samples integrating a 40 yr time sequence from 1940 to 1980 which were collected from the walls of a 6 m deep pit at stake D 55 in Adelie Land, East Antarctica. Measured concentrations, which are among the lowest ones ever measured in Antarctic snows, are found not to have significantly increased during the investigated time period, with the possible exception of Pb for which there might have been a significant increase after the mid 1960's. For this last metal, measured concentrations in the 1940's are about 6-fold higher than in Antarctic Holocene ice several thousand years old, which indicates that a large fraction of the anthropogenic increase for Pb probably occurred before the 1940's.     

Plio-pleistocene volcanism in the Andean Cordillera of Central Chile (33∘ – 40∘ S. L.)

Recent field studies in the Andean Cordillera of Central Chile (33–40 S. L.) have shown a widespread distribution around the Chile-Argentina border of pliopleistocene volcanic and pyroclastic flow (5-1 m. y. K/Ar). The older ages are found in Rio Blanco (Santiago) area and the younger in the Cola de Zorro area. They cover horizontal to sub-horizontally, with strong unconformity their meso-cenozoic basement.In the Rio Blanco area the most silicic rocks are dactic and rhyolitic ignimbrites and lava flows. They are similar to the Rhyolitic Formation (Zeil andPichler, 1967) of northern Chile.South of 36 S. L. most of the rocks are calcalkaline basalts and andesites except for the samples from the Pino Hachado area, which plot nearRittman's alkaline field. Chemical inhomogenety of the plio-pleistocene volcanic rocks is thus present in the Andes of Central Chile.

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Zusammenfassung Neue Arbeiten über die Geologie der Cordillera de los Andes im zentralen Abschnitt Chiles (33–40 S) haben eine enorme Verbreitung von plio/pleistozänen Vulkaniten (5-1 m. a.) vor allem in der Grenzregion mit Argentinien ergeben. Die höheren Alter fand man im Gebiet von Rio Blanco (Santiago) und die jüngsten im Gebiet von Cola de Zorro.Die Vulkanite bedecken mit einer horizontalen bis subhorizontalen Verbreitung und mit einer scharfen Diskordanz alle Gesteinsserien des Mesozoikums und Känozoikums.Im Gebiet von Rio Blanco handelt es sich um Ignimbrite rhyolitischer und dacitischer Zusammensetzung. Die kieselsäurereichsten Proben sind ähnlich den Gesteinen der Rhyolit-Formation vonZeil &Pichler (1967) in Nordchile.Südlich von 36 S hat die Mehrheit der Proben eine andesitische und basaltische Zusammensetzung. Es sind kalkalkaline Gesteine mit Ausnahme der Proben von Pino Hachado, die einen starken alkalinen Trend nach dem Diagramm vonRittmann haben. Auf diese Weise ergibt sich eine chemische Inhomogenität bei den plio/pleistozänen Vulkaniten von Zentralchile.

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Resumen Los más recientes trabajos de geología de campo en la Cordillera de los Andes de Chile Central (33–40 L. S.) han evidenciado enormes extensiones de rocas volcánicas pliopleistocénicas (5-1 m. a.) sobre todo en el área limítrofe con Argentina. Las mayores edades fueron encontradas en el area de Rio Blanco (Santiago) y las más jóvenes en el area de Cola de Zorro.Las rocas volcánicas plio-pleistocénicas cubren con disposición horizontal a subhorizontal y con fuerte discordancia a todas las rocas subyacentes del Meso y Cenozoico.En el area de Río Blanco las rocas son ignimbritas de composición riolítica a dacítica y corresponden a las muestras más silícicas similar a rocas de la Formación Riolítica del norte de Chile deZeil yPichler (1967).Al sur del paralelo 36 S la mayoría de las muestras son de composición andesítica y basáltica de naturaleza calcoalcalina excepto las muestras de Pino Hachado que presentan fuerte afînidad alcalina según el diagrama deRittmann. De esta manera se muestra que existe inhomogeneidad química en las rocas volcánicas plios-pleistocénicas de Chile Central.

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Studie über Höhenschwankungen der F2-Schicht: III

Zusammenfassung Es muss unterschieden werden zwischen den (scheinbaren) Minimalhöhen der F2-Schicht und jenen Höhen, in denen sich das Miximum der Elektronenkonzentration befindt. Es wird gezeist, dass sich für Statinen in Aequatornähe diese beiden Gebiete der F2-Schicht ganz verschieden verhalten; aus der Tatsache, dass die untere Begrenzung mit zunehmender Sonnentätigkeit abwts sinkt, während gleichzeitig die Höhe für die maximale Elektronenkonzentration anwächst, wird auf eine Veränderung der Schichtdicke geschlossen, die von der wechselnden Sonnenaktivität étroite avec l'activité solaire.

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Résumé La distinction entre la hauteur virtuelle minimum de la couche F2 et la hauteur vituelle où se trouve le maximum de la concentration 'eléctronique est nécessaire. On Montre que ces deux régions sont tré différentes pour les stations situées près de l'équateur. Etant donné que la base de la couche F2 s'abaisse pendant la période de croissance du cycle solaire, tandis que la hauteur de la concentraion éléctronique du maximmum augmente, on en conclu que l'épaisseur est soumis à des variations en relation étroite avec l'activité solaire.

     

Universal time from VLBI single-baseline observations during CONT08

The IVS Intensive sessions are single-baseline, 1-h VLBI sessions carried out everyday in order to determine Universal Time (UT1). We investigate different possibilities to improve the results of such sessions. We do this investigation by extracting 2-h single-baseline sessions from the CONT08 data set. These are analysed like normal Intensives, and the results are compared to the results of the analysis of the full CONT08 data set. We find that tropospheric asymmetry is the major error source for the single-baseline sessions. It is possible to improve the accuracy of the estimated UT1 either by using accurate a priori tropospheric gradients or by estimating gradients in the data analysis.