Hydrological trends and the evolution of catchment research in the Alptal valley,central Switzerland     

Manfred Stähli  Jan Seibert  James W. Kirchner  Jana von Freyberg  Ilja van Meerveld 《水文研究》2021,35(4):e14113

When the observation of small headwater catchments in the pre-Alpine Alptal valley (central Switzerland) started in the late 1960s, the researchers were mainly interested in questions related to floods and forest management. Investigations of geomorphological processes in the steep torrent channels followed in the 1980s, along with detailed observations of biogeochemical and ecohydrological processes in individual forest stands. More recently, research in the Alptal has addressed the impacts of climate change on water supply and runoff generation. In this article, we describe, for the first time, the evolution of catchment research at Alptal, and present new analyses of long-term trends and short-term hydrologic behaviour. Hydrometeorological time series from the past 50 years show substantial interannual variability, but only minimal long-term trends, except for the ~2°C increase in mean annual air temperature over the 50-year period, and a corresponding shift towards earlier snowmelt. Similar to previous studies in larger Alpine catchments, the decadal variations in mean annual runoff in Alptal's small research catchments reflect the long-term variability in annual precipitation. In the Alptal valley, the most evident hydrological trends were observed in late spring and are related to the substantial change in the duration of the snow cover. Streamflow and water quality are highly variable within and between hydrological events, suggesting rapid shifts in flow pathways and mixing, as well as changing connectivity of runoff-generating areas. This overview illustrates how catchment research in the Alptal has evolved in response to changing societal concerns and emerging scientific questions.  相似文献   

On the possibility of earth-type habitable planets around 47 UMa     

Manfred Cuntz  Werner von Bloh  Siegfried Franck 《Icarus》2003,162(1):214-221

We investigate whether Earth-type habitable planets can in principle exist in the planetary system of 47 UMa. The system of 47 UMa consists of two Jupiter-size planets beyond the outer edge of the stellar habitable zone, and thus resembles our own Solar System most closely compared to all exosolar planetary systems discovered so far. Our study of habitability deliberately follows an Earth-based view according to the concept of Franck and colleagues, which assumes the long-term possibility of photosynthetic biomass production under geodynamic conditions. Consequently, a broad variety of climatological, biogeochemical, and geodynamical processes involved in the generation of photosynthesis-driven life conditions is taken into account. The stellar luminosity and the age of the star/planet system are of fundamental importance for planetary habitability. Our study considers different types of planetary continental growth models and takes into account a careful assessment of the stellar parameters. In the event of successful formation and orbital stability, two subjects of intense research, we find that Earth-type habitable planets around 47 UMa are in principle possible! The likelihood of those planets is increased if assumed that 47 UMa is relatively young (?6 Gyr) and has a relatively small stellar luminosity as permitted by the observational range of those parameters.  相似文献   

Scanning electron microscopy,cathodoluminescence, and Raman spectroscopy of experimentally shock‐metamorphosed quartzite     

Arnold Gucsik  Christian Koeberl  Franz Brandsttter  Eugen Libowitzky  Wolf Uwe Reimold 《Meteoritics & planetary science》2003,38(8):1187-1197

Abstract— We studied unshocked and experimentally (at 12, 25, and 28 GPa, with 25, 100, 450, and 750°C pre‐shock temperatures) shock‐metamorphosed Hospital Hill quartzite from South Africa using cathodoluminescence (CL) images and spectroscopy and Raman spectroscopy to document systematic pressure or temperature‐related effects that could be used in shock barometry. In general, CL images of all samples show CL‐bright luminescent patchy areas and bands in otherwise nonluminescent quartz, as well as CL‐dark irregular fractures. Fluid inclusions appear dominant in CL images of the 25 GPa sample shocked at 750°C and of the 28 GPa sample shocked at 450°C. Only the optical image of our 28 GPa sample shocked at 25°C exhibits distinct planar deformation features (PDFs). Cathodoluminescence spectra of unshocked and experimentally shocked samples show broad bands in the near‐ultraviolet range and the visible light range at all shock stages, indicating the presence of defect centers on, e.g., SiO₄ groups. No systematic change in the appearance of the CL images was obvious, but the CL spectra do show changes between the shock stages. The Raman spectra are characteristic for quartz in the unshocked and 12 GPa samples. In the 25 and 28 GPa samples, broad bands indicate the presence of glassy SiO₂, while high‐pressure polymorphs are not detected. Apparently, some of the CL and Raman spectral properties can be used in shock barometry.  相似文献   

2D/3D Dust Continuum Radiative Transfer Codes to Analyze and Predict VLTI Observations     

I. Pascucci  Th. Henning  J. Steinacker  S. Wolf 《Astrophysics and Space Science》2003,286(1-2):113-118

Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric device MIDI. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

    

Tietze Wolf 《GeoJournal》1991,25(4):440

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Weak lensing with COMBO-17: estimation and removal of intrinsic alignments     

Catherine Heymans  Michael Brown  Alan Heavens  Klaus Meisenheimer  y Taylor  Christian Wolf 《Monthly notices of the Royal Astronomical Society》2004,347(3):895-908

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Readout Techniques for Drift and Low Frequency Noise Rejection in Infrared Arrays     

Gert Finger  Reinhold J. Dorn  Alan W. Hoffman  Hamid Mehrgan  Manfred Meyer  Alan F. M. Moorwood  Joerg Stegmeier 《Experimental Astronomy》2002,14(2):117-127

Three different methods are presented to subtract thermal drifts and low-frequency noise from the signal of infrared array. The first is dead pixels with open Indium bumps, the second is reference output as implemented on the Hawaii2 multiplexer, and the third is dark pixels to emulate reference cells having a capacity connected to the gate of the unit cell field-effect transistor (FET). The third method is the most effective and yields a reduction in readout noise from15.4–9.4 erms. A novel method will be described to extend this readout technique to the Aladdin 1 K × 1 K InSb array. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Viscoelastodynamics of A Stratified, Compressible Planet: Incremental Field Equations and Short- and Long-Time Asymptotes     

Detlef Wolf 《Geophysical Journal International》1991,104(2):401-417

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Modelling the effect of low soil temperatures on transpiration by Scots pine     

Per‐Erik Mellander  Manfred Sthli  David Gustafsson  Kevin Bishop 《水文研究》2006,20(9):1929-1944

For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring‐early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70‐year‐old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high‐latitude stands. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

On Boussinesq's problem for Maxwell continua subject to an external gravity field     

Detlef Wolf 《Geophysical Journal International》1985,80(1):275-279

Summary. Boussinesq's problem is solved for a uniform and incompressible Maxwell half-space subject to an external gravity field. The solution is based on momentum equations which account for stress advection in the hydrostatically pre-stressed continuum during its deformation. The analysis shows that disregarding the pre-stress term renders the theoretical stress distribution incorrect and the deformation singular in the inviscid limit of the Maxwell continuum. Our solution is contrasted with a recently published alternative solution of the same problem, where regularity in the inviscid limit was forced by modified boundary conditions.  相似文献