Snowpack monitoring with upward-looking radar systems towards improved avalanche risk prediction
Final Report Abstract
The upGPR system will be transferred to polar regions to monitor liquid water percolation, snow accumulation and firn densification in continuous matter over several seasons. So far, such data are not available. Several public authorities declared already their interest in running an upGPR system for autonomous snowpack monitoring in hazardous area. We were able to demonstrate the capability of upGPR technology to produce long-term monitoring of liquid water behavior in natural snow. Such data can and is used to evaluate snow cover modeling approaches. There is a distinct need for the ability of continuous LWC monitoring to improve our knowledge on water transport in layered snowpacks. For instance, the implementation of upGPR-determined water retention per day improve even very simple model approaches to reduce offsets of simulated outflow sums to measurements to below 10%. A major technical breakthrough has been the combination with GPS receivers placed at the soil surface. Such a combination enables accurate derivation of snowpack parameters like snow height, SWE or bulk LWC independent from above snow installations or conventional measurements of the snow height. Such a combination is capable to provide continuous data in avalanche starting zones as well as drift areas. For hydrological purposes drift areas are of high interest since here a high proportion of the total accumulation mass of the entire catchment can be stored. To date, however, knowledge on drift formation is still very poor. As a consequence, model approaches fail to model redistribution of snow masses into such areas. Regarding achievements of the work packages described for this project extension, we conclude that WP 1 and 3 have been successfully completed and for some minor parts of the respective WP’s, we have provided encouraging results to further analyze for instance snow and weather conditions, which promote the formation of preferential flow paths in snow or allow for the direct implementation of upGPR derived LWC data for avalanche hazard assessment. Concerning the hardware development of multi-offset FMCW arrays (WP2), we have to state that such low-cost bowtie antennas are not capable to provide adequate data for continuous snow-height and dielectric property monitoring. Such technical difficulties are not surprising regarding the price range in which regular FMCW systems are located in comparison to the here deployed electronical parts. However, the enormous possible knowledge gain in case of successful implementation of such low-power/ low-cost FMCW systems still justifies the feasibility study in retrospect.
Publications
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(2014). Assessing Approaches for Determination of Liquid Water in Snow, EOS 95, 36, 9, 328
Eisen, O. and Schweizer, J.
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(2014): Continuous snowpack monitoring using upward-looking groundpenetrating radar technology. In Journal of Glaciology 60 (221), pp. 509–525
Schmid, Lino; Heilig, Achim; Mitterer, Christoph; Schweizer, Jürg; Maurer, Hansruedi; Okorn, Robert; Eisen, Olaf
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(2014): Upward-looking L-band FMCW radar for snow cover monitoring. In Cold Regions Science and Technology 103, pp. 31–40
Okorn, Robert; Brunnhofer, Georg; Platzer, Thomas; Heilig, Achim; Schmid, Lino; Mitterer, Christoph et al.
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(2015), A novel sensor combination (upGPR-GPS) to continuously and nondestructively derive snow cover properties. Geophys. Res. Lett., 42, 3397–3405
Schmid, L., F. Koch, A. Heilig, M. Prasch, O. Eisen, W. Mauser, and J. Schweizer
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(2015), Seasonal and diurnal cycles of liquid water in snow - Measurements and modeling, J. Geophys. Res. Earth Surf., 120
Heilig, A., C. Mitterer, L. Schmid, N. Wever, J. Schweizer, H.-P. Marshall, and O. Eisen
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(2015): Verification of the multi-layer SNOWPACK model with different water transport schemes. In The Cryosphere Discuss. 9 (2), pp. 2655–2707
Wever, N.; Schmid, L.; Heilig, A.; Eisen, O.; Fierz, C.; Lehning, M.
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(2016): A synthetic study to assess the applicability of full-waveform inversion to infer snow stratigraphy from upGPR radar data. Geophysics, 81(1), WA213-WA223
Schmid, L., Schweizer, J., Bradford, J. and Maurer, H.
