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  • Online-Ressource  (3)
  • Wiley  (3)
  • 2015-2019  (3)
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  • Online-Ressource  (3)
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  • Wiley  (3)
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  • 2015-2019  (3)
Jahr
  • 1
    Online-Ressource
    Online-Ressource
    Wiley ; 2019
    In:  Hydrological Processes Vol. 33, No. 19 ( 2019-09-15), p. 2502-2522
    In: Hydrological Processes, Wiley, Vol. 33, No. 19 ( 2019-09-15), p. 2502-2522
    Kurzfassung: Topography and landscape characteristics affect the storage and release of water and, thus, groundwater dynamics and chemistry. Quantification of catchment scale variability in groundwater chemistry and groundwater dynamics may therefore help to delineate different groundwater types and improve our understanding of which parts of the catchment contribute to streamflow. We sampled shallow groundwater from 34 to 47 wells and streamflow at seven locations in a 20‐ha steep mountainous catchment in the Swiss pre‐Alps, during nine baseflow snapshot campaigns. The spatial variability in electrical conductivity, stable water isotopic composition, and major and trace ion concentrations was large and for almost all parameters larger than the temporal variability. Concentrations of copper, zinc, and lead were highest at sites that were relatively dry, whereas concentrations of manganese and iron were highest at sites that had persistent shallow groundwater levels. The major cation and anion concentrations were only weakly correlated to individual topographic or hydrodynamic characteristics. However, we could distinguish four shallow groundwater types based on differences from the catchment average concentrations: riparian zone‐like groundwater, hillslopes and areas with small upslope contributing areas, deeper groundwater, and sites characterized by high magnesium and sulfate concentrations that likely reflect different bedrock material. Baseflow was not an equal mixture of the different groundwater types. For the majority of the campaigns, baseflow chemistry most strongly resembled riparian‐like groundwater for all but one subcatchment. However, the similarity to the hillslope‐type groundwater was larger shortly after snowmelt, reflecting differences in hydrologic connectivity. We expect that similar groundwater types can be found in other catchments with steep hillslopes and wet areas with shallow groundwater levels and recommend sampling of groundwater from all landscape elements to understand groundwater chemistry and groundwater contributions to streamflow.
    Materialart: Online-Ressource
    ISSN: 0885-6087 , 1099-1085
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2019
    ZDB Id: 1479953-4
    SSG: 14
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    Wiley ; 2019
    In:  Astronomische Nachrichten Vol. 340, No. 4 ( 2019-05), p. 351-356
    In: Astronomische Nachrichten, Wiley, Vol. 340, No. 4 ( 2019-05), p. 351-356
    Kurzfassung: The tidal disruption of a star by a nuclear supermassive black hole was predicted in the 1970s and first confirmed by soft X‐ray flares seen from quiescent galaxies in the ROSAT all‐sky survey. We report here on the discovery of a new candidate tidal disruption event, 1RXS J075908.8 + 074835, from the ROSAT bright source catalog, which faded by a factor  〉  100 in 20 years. Similar events have continued to be found in XMM‐Newton and Chandra data and more recently, flares in large‐area hard X‐ray, ultraviolet (UV) and optical transient surveys have also been attributed to the same phenomenon. Each of these spectral components, sometimes complemented by radio and IR activity, have their own timescale and possibly physical mechanism. Current models and simulations revolve around trying to explain how the energy released by the fall back of stellar debris in the gravitational well of the black hole is converted into radiation in each wave band. We look at the connection between optical, UV, and X‐ray emission and illustrate a dichotomy between X‐ray and optically dominated tidal disruption event (TDE), which is currently unexplained. We look at the observations that are needed to make further breakthroughs in the field and assess the optimum follow‐up strategies needed for events discovered in future large survey missions such as extended Roentgen Survey with an Imaging Telescope Array (eROSITA), the Einstein Probe, and Large Synoptic Survey Telescope (LSST). HIgh‐energy LIght‐curve GeneraTor (HILIGT), a useful new tool for comparing fluxes and upper limits between missions, is presented.
    Materialart: Online-Ressource
    ISSN: 0004-6337 , 1521-3994
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2019
    ZDB Id: 2025762-4
    ZDB Id: 2171222-0
    SSG: 16,12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    Wiley ; 2015
    In:  Ecohydrology Vol. 8, No. 4 ( 2015-06), p. 695-713
    In: Ecohydrology, Wiley, Vol. 8, No. 4 ( 2015-06), p. 695-713
    Kurzfassung: The onshore movement of marine fog is a common occurrence during summer months along much of the contiguous US Pacific Coast. Because the fog season tends to occur during the precipitation‐free dry season, any additional input of moisture or reduction in loss of moisture through evapotranspiration provided by the marine layer can be an important factor in local hydrologic systems. To quantify some of the effects of fog on regional dry‐season hydrology, a study site within the Santa Cruz Mountains of central California was established. The fog‐laden coastside and predominately fog‐free San Francisco Bay side of the study area provide an excellent opportunity to assess the impacts of the presence and absence of fog on ecohydrological processes. Streamflow, fog drip, and soil moisture were measured from May to September. Fog drip was essentially nonexistent on the bayside and highly variable on the coastside. Maximum rates and seasonal totals of drip occurred within stands of mature conifers ( Sequoia sempervirens and Pseudotsuga menziesii ) along exposed, often windy ridgelines. Fog‐drip totals up to 961 mm were recorded over 2·5 months. Consequently, frequent infiltration events to depths of 23 cm were documented. Over the course of the study, soil moisture levels at high‐fog‐drip locations either increased or were equivalent to spring conditions at the onset of data collection. Increases of flow in coastside streams, under otherwise receding conditions, were found to coincide with fog and fog‐drip events. These results confirm that the presence of fog can significantly affect dry‐season hydrologic conditions of some coastal locations. Copyright © 2014 John Wiley & Sons, Ltd.
    Materialart: Online-Ressource
    ISSN: 1936-0584 , 1936-0592
    URL: Issue
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2015
    ZDB Id: 2418105-5
    SSG: 12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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