International Snow Science Workshop Proceedings - Montana State University Library

Item: SNOW WATER EQUIVALENT RETRIEVAL FROM SENTINEL-1 INSAR USING A COLLOCATED ACTIVE REFLECTOR AND GNSS REFRACTOMETRY

• • Title: SNOW WATER EQUIVALENT RETRIEVAL FROM SENTINEL-1 INSAR USING A COLLOCATED ACTIVE REFLECTOR AND GNSS REFRACTOMETRY

    Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026

    Authors:

    • Paolo Perret  [ University of Pavia, Department of Electrical, Computer and Biomedical Engineering, Pavia, Italy ]  [ Fondazione Montagna Sicura, Courmayeur, Italy ]
    • Pedro Espín-López  [ Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Spain ]
    • Guido Luzi  [ Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Spain ]
    • Martina Lodigiani  [ Fondazione Montagna Sicura, Courmayeur, Italy ]
    • Lorenzo Silvestri  [ University of Pavia, Department of Electrical, Computer and Biomedical Engineering, Pavia, Italy ]
    • Tommaso Congiu  [ Fondazione Montagna Sicura, Courmayeur, Italy ]
    • Fabrizio Troilo  [ University of Pavia, Department of Electrical, Computer and Biomedical Engineering, Pavia, Italy ]
    • Francesco Zucca  [ University of Pavia, Department of Earth and Environmental Sciences, Pavia, Italy ]
    • Marco Pasian  [ University of Pavia, Department of Electrical, Computer and Biomedical Engineering, Pavia, Italy ]

    Date: 2026-09-28

    Abstract: Spaceborne C-band interferometry is sensitive to changes in snow water equivalent (SWE), but it needs a phase reference that is absolute, unambiguous, and restricted to dry snow. We address that requirement with a station that combines a ground-flush C-band active reflector (AR) with a collocated GNSS refractometry antenna, installed at 2166 m in the Aosta Valley, Italian Alps. Both instruments sit at ground level and spend the winter beneath the snowpack. This paper describes the station, characterises the ground reference it produced over the winter of 2025–2026, and gives a first reading of the radar side. The GNSS antenna returned half-hourly SWE from 19 November to 17 May, 179 days at 82 % availability, with an observed maximum of 292 mm w.e. on 15 March. Against 22 manual snow pits dug beside the station, the 18 that could be paired show a bias of −4.7 mm and a root mean square difference of 14.4 mm, closer during accumulation (12.3 mm) than during ablation (17.9 mm). Compared with a SNOWPACK simulation driven by the local weather station, the GNSS record shows a small but seasonally structured bias, about +13 mm while the pack builds and −13 mm while it melts. On one of the two Sentinel-1 tracks that image the site, the interferometric phase of the reflector, converted with the dry-snow relation and referenced to the GNSS at activation, follows the GNSS record to 6.6 mm and the pits to 10.6 mm through the dry season, once the integer cycles hidden by storms are restored, here by hand. The reflector's signal falls to the clutter level at melt onset, marking the end of the dry-snow regime. The station therefore delivers an autonomous, verifiable SWE reference next to a controlled radar target whose phase can be read as SWE. Automated resolution of the phase ambiguity and the transfer of the reference to the surrounding basin are the subject of ongoing work.

    Object ID: ISSW2026_P3.23.pdf

    DOI: https://doi.org/10.15788/1790099130

    Language of Article: English

    Presenter(s): Paolo Perret

    Keywords: snow water equivalent, GNSS refractometry, active radar reflector, InSAR, Sentinel-1, alpine snowpack

    Page Number(s): 1105 - 1110

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