Abstract
Abstract. GFZ (German Research Centre for Geosciences) set up the Zugspitze Geodynamic Observatory Germany with a worldwide unique installation of a superconducting gravimeter at the summit of Mount Zugspitze on top of the Partnach spring catchment. This high alpine catchment is well instrumented, acts as natural lysimeter and has significant importance for water supply to its forelands, with a large mean annual precipitation of 2080 mm and a long seasonal snow cover period of 9 months, while showing a high sensitivity to climate change. However, regarding the majority of alpine regions worldwide, there is only limited knowledge on temporal water storage variations due to sparsely distributed hydrological and meteorological sensors and the large variability and complexity of signals in alpine terrain. This underlines the importance of well-equipped areas such as Mount Zugspitze serving as natural test laboratories for improved monitoring, understanding and prediction of alpine hydrological processes. The observatory superconducting gravimeter, OSG 052, supplements the existing sensor network as a novel hydrological sensor system for the direct observation of the integral gravity effect of total water storage variations in the alpine research catchment at Zugspitze. Besides the experimental set-up and the available data sets, the gravimetric methods and gravity residuals are presented based on the first 27 months of observations from 29 December 2018 to 31 March 2021. The snowpack is identified as being a primary contributor to seasonal water storage variations and, thus, to the gravity residuals with a signal range of up to 750 nm s−2 corresponding to 1957 mm snow water equivalent measured with a snow scale at an altitude of 2420 m at the end of May 2019. Hydro-gravimetric sensitivity analysis reveal a snow–gravimetric footprint of up to 4 km distance around the gravimeter, with a dominant gravity contribution from the snowpack in the Partnach spring catchment. This shows that the hydro-gravimetric approach delivers representative integral insights into the water balance of this high alpine site.
Highlights
One of the grand societal challenges is ensuring sufficient water supply under climate change conditions
The achieved accuracy is sufficient with regard to gravity residuals with a range of 750 nm s−2 (Fig. 3g), as amplitude factor deviations of 1 nm s−2 V−1 correspond to maximum deviations of 1 nm s−2 in gravity residuals, which represents a conservative estimate of the accuracy of the gravity observations at Zugspitze Geodynamic Observatory Germany (ZUGOG)
The superconducting gravimeter OSG 052 is introduced as a novel hydrological sensor for the direct observation of the integral gravity effect of total water storage variations in the high alpine Partnach spring catchment (Research Catchment Zugspitze – RCZ), and a high-quality and publicly available continuous gravity time series of 27 months is provided
Summary
One of the grand societal challenges is ensuring sufficient water supply under climate change conditions. Arising from these studies were the small number of cloudfree remote sensing scenes in the visible and near-infrared spectrum to derive spatially distributed snow cover maps at high temporal resolutions and the limited spatial extent of the terrestrial photogrammetry and lidar observations in the RCZ (Härer et al, 2016; Weber et al, 2016, 2020). Both photogrammetry and lidar observation techniques are only capable of measuring snow heights, but not hydrologically relevant SWE values, directly and rely on additional snow density data from local snow pit or snow weight measurements.
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