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  1. Article ; Online: The role of thermokarst evolution in debris flow initiation (Hüttekar Rock Glacier, Austrian Alps)

    S. Seelig / T. Wagner / K. Krainer / M. Avian / M. Olefs / K. Haslinger / G. Winkler

    Natural Hazards and Earth System Sciences, Vol 23, Pp 2547-

    2023  Volume 2568

    Abstract: A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost ... ...

    Abstract A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost degradation and drainage network development within the rock glacier initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120 000 m 3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. We present a systematic analysis of destabilizing factors to deduce the failure mechanism. The identification and evaluation of individual factors reveals a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of a thermokarst drainage network. Progressively changing groundwater flow and storage patterns within the frozen sediment accumulation governed the slope stability of the rock glacier front. Our results demonstrate the hazard potential of active rock glaciers due to their large amount of mobilizable sediment, dynamically changing internal structure, thermokarst lake development, and substantial water flow along a rapidly evolving channel network.
    Keywords Environmental technology. Sanitary engineering ; TD1-1066 ; Geography. Anthropology. Recreation ; G ; Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 333 ; 550
    Language English
    Publishing date 2023-07-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Sentinel-1 snow depth retrieval at sub-kilometer resolution over the European Alps

    H. Lievens / I. Brangers / H.-P. Marshall / T. Jonas / M. Olefs / G. De Lannoy

    The Cryosphere, Vol 16, Pp 159-

    2022  Volume 177

    Abstract: Seasonal snow is an essential water resource in many mountain regions. However, the spatio-temporal variability in mountain snow depth or snow water equivalent (SWE) at regional to global scales is not well understood due to the lack of high-resolution ... ...

    Abstract Seasonal snow is an essential water resource in many mountain regions. However, the spatio-temporal variability in mountain snow depth or snow water equivalent (SWE) at regional to global scales is not well understood due to the lack of high-resolution satellite observations and robust retrieval algorithms. We investigate the ability of the Sentinel-1 mission to monitor snow depth at sub-kilometer (100 m , 500 m , and 1 km ) resolutions over the European Alps for 2017–2019. The Sentinel-1 backscatter observations, especially in cross-polarization, show a high correlation with regional model simulations of snow depth over Austria and Switzerland. The observed changes in radar backscatter with the accumulation or ablation of snow are used in an empirical change detection algorithm to retrieve snow depth. The algorithm includes the detection of dry and wet snow conditions. Compared to in situ measurements at 743 sites in the European Alps, dry snow depth retrievals at 500 m and 1 km resolution have a spatio-temporal correlation of 0.89. The mean absolute error equals 20 % –30 % of the measured values for snow depths between 1.5 and 3 m . The performance slightly degrades for retrievals at the finer 100 m spatial resolution as well as for retrievals of shallower and deeper snow. The results demonstrate the ability of Sentinel-1 to provide snow estimates in mountainous regions where satellite-based estimates of snow mass are currently lacking. The retrievals can improve our knowledge of seasonal snow mass in areas with complex topography and benefit a number of applications, such as water resource management, flood forecasting, and numerical weather prediction. However, future research is recommended to further investigate the physical basis of the sensitivity of Sentinel-1 backscatter observations to snow accumulation.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 551
    Language English
    Publishing date 2022-01-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Obtaining sub-daily new snow density from automated measurements in high mountain regions

    K. Helfricht / L. Hartl / R. Koch / C. Marty / M. Olefs

    Hydrology and Earth System Sciences, Vol 22, Pp 2655-

    2018  Volume 2668

    Abstract: The density of new snow is operationally monitored by meteorological or hydrological services at daily time intervals, or occasionally measured in local field studies. However, meteorological conditions and thus settling of the freshly deposited snow ... ...

    Abstract The density of new snow is operationally monitored by meteorological or hydrological services at daily time intervals, or occasionally measured in local field studies. However, meteorological conditions and thus settling of the freshly deposited snow rapidly alter the new snow density until measurement. Physically based snow models and nowcasting applications make use of hourly weather data to determine the water equivalent of the snowfall and snow depth. In previous studies, a number of empirical parameterizations were developed to approximate the new snow density by meteorological parameters. These parameterizations are largely based on new snow measurements derived from local in situ measurements. In this study a data set of automated snow measurements at four stations located in the European Alps is analysed for several winter seasons. Hourly new snow densities are calculated from the height of new snow and the water equivalent of snowfall. Considering the settling of the new snow and the old snowpack, the average hourly new snow density is 68 kg m −3 , with a standard deviation of 9 kg m −3 . Seven existing parameterizations for estimating new snow densities were tested against these data, and most calculations overestimate the hourly automated measurements. Two of the tested parameterizations were capable of simulating low new snow densities observed at sheltered inner-alpine stations. The observed variability in new snow density from the automated measurements could not be described with satisfactory statistical significance by any of the investigated parameterizations. Applying simple linear regressions between new snow density and wet bulb temperature based on the measurements' data resulted in significant relationships ( r 2 > 0.5 and p ≤ 0.05) for single periods at individual stations only. Higher new snow density was calculated for the highest elevated and most wind-exposed station location. Whereas snow measurements using ultrasonic devices and snow pillows are appropriate for calculating station ...
    Keywords Technology ; T ; Environmental technology. Sanitary engineering ; TD1-1066 ; Geography. Anthropology. Recreation ; G ; Environmental sciences ; GE1-350
    Subject code 551
    Language English
    Publishing date 2018-05-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  4. Article ; Online: Correction of broadband snow albedo measurements affected by unknown slope and sensor tilts

    U. Weiser / M. Olefs / W. Schöner / G. Weyss / B. Hynek

    The Cryosphere, Vol 10, Iss 2, Pp 775-

    2016  Volume 790

    Abstract: Geometric effects induced by the underlying terrain slope or by tilt errors of the radiation sensors lead to an erroneous measurement of snow or ice albedo. Consequently, artificial diurnal albedo variations in the order of 1–20 % are observed. The ... ...

    Abstract Geometric effects induced by the underlying terrain slope or by tilt errors of the radiation sensors lead to an erroneous measurement of snow or ice albedo. Consequently, artificial diurnal albedo variations in the order of 1–20 % are observed. The present paper proposes a general method to correct tilt errors of albedo measurements in cases where tilts of both the sensors and the slopes are not accurately measured or known. We demonstrate that atmospheric parameters for this correction model can either be taken from a nearby well-maintained and horizontally levelled measurement of global radiation or alternatively from a solar radiation model. In a next step the model is fitted to the measured data to determine tilts and directions of sensors and the underlying terrain slope. This then allows us to correct the measured albedo, the radiative balance and the energy balance. Depending on the direction of the slope and the sensors a comparison between measured and corrected albedo values reveals obvious over- or underestimations of albedo. It is also demonstrated that differences between measured and corrected albedo are generally highest for large solar zenith angles.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 551
    Language English
    Publishing date 2016-04-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  5. Article ; Online: Correction of albedo measurements due to unknown geometry

    U. Weiser / M. Olefs / W. Schöner / G. Weyss / B. Hynek

    The Cryosphere Discussions, Vol 9, Iss 3, Pp 2709-

    2015  Volume 2744

    Abstract: The diurnal albedo variation of glaciers on clear sky days can be relatively high due to geometric effects induced by tilt errors. In the present paper, these tilt errors of albedo measurements are corrected in cases where tilts of both, the sensors and ... ...

    Abstract The diurnal albedo variation of glaciers on clear sky days can be relatively high due to geometric effects induced by tilt errors. In the present paper, these tilt errors of albedo measurements are corrected in cases where tilts of both, the sensors and the slopes are not accurately measured. For this method of correction, a nearby reference measurement with a horizontally levelled sensor is needed to determine atmospheric parameters. Based on that a model is developed that is fitted to the measured data to determine tilts and directions of sensors and slopes, which vary daily due to changing atmospheric conditions and snow cover. Once these parameters are determined, the albedo, the radiative balance and the energy balance can be corrected. The differences between measured and corrected values show an obvious under- or overestimation of albedo, depending on the direction of the slope. It is also demonstrated that the difference between measured and corrected albedo is highest for high solar zenith angles.
    Keywords Science ; Q ; Geology ; QE1-996.5 ; Petrology ; QE420-499 ; Dynamic and structural geology ; QE500-639.5
    Subject code 620
    Language English
    Publishing date 2015-05-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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    Inter-library loan at ZB MED

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  6. Article ; Online: Baseline Surface Radiation Network (BSRN)

    A. Driemel / J. Augustine / K. Behrens / S. Colle / C. Cox / E. Cuevas-Agulló / F. M. Denn / T. Duprat / M. Fukuda / H. Grobe / M. Haeffelin / G. Hodges / N. Hyett / O. Ijima / A. Kallis / W. Knap / V. Kustov / C. N. Long / D. Longenecker /
    A. Lupi / M. Maturilli / M. Mimouni / L. Ntsangwane / H. Ogihara / X. Olano / M. Olefs / M. Omori / L. Passamani / E. B. Pereira / H. Schmithüsen / S. Schumacher / R. Sieger / J. Tamlyn / R. Vogt / L. Vuilleumier / X. Xia / A. Ohmura / G. König-Langlo

    Earth System Science Data, Vol 10, Pp 1491-

    structure and data description (1992–2017)

    2018  Volume 1501

    Abstract: Small changes in the radiation budget at the earth's surface can lead to large climatological responses when persistent over time. With the increasing debate on anthropogenic influences on climatic processes during the 1980s the need for accurate ... ...

    Abstract Small changes in the radiation budget at the earth's surface can lead to large climatological responses when persistent over time. With the increasing debate on anthropogenic influences on climatic processes during the 1980s the need for accurate radiometric measurements with higher temporal resolution was identified, and it was determined that the existing measurement networks did not have the resolution or accuracy required to meet this need. In 1988 the WMO therefore proposed the establishment of a new international Baseline Surface Radiation Network (BSRN), which should collect and centrally archive high-quality ground-based radiation measurements in 1 min resolution. BSRN began its work in 1992 with 9 stations; currently (status 2018-01-01), the network comprises 59 stations (delivering data to the archive) and 9 candidates (stations recently accepted into the network with data forthcoming to the archive) distributed over all continents and oceanic environments. The BSRN database is the World Radiation Monitoring Center (WRMC). It is hosted at the Alfred Wegener Institute (AWI) in Bremerhaven, Germany, and now offers more than 10 300 months of data from the years 1992 to 2017. All data are available at https://doi.org/10.1594/PANGAEA.880000 free of charge.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Language English
    Publishing date 2018-08-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

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