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Medientyp:
E-Artikel
Titel:
Snow water equivalent change mapping from slope-correlated synthetic aperture radar interferometry (InSAR) phase variations
Beteiligte:
Eppler, Jayson;
Rabus, Bernhard;
Morse, Peter
Erschienen:
Copernicus GmbH, 2022
Erschienen in:
The Cryosphere, 16 (2022) 4, Seite 1497-1521
Sprache:
Englisch
DOI:
10.5194/tc-16-1497-2022
ISSN:
1994-0424
Entstehung:
Anmerkungen:
Beschreibung:
Abstract. Area-based measurements of snow water equivalent (SWE) are important for understanding earth system processes such as glacier mass balance, winterhydrological storage in drainage basins, and ground thermal regimes. Remote sensing techniques are ideally suited for wide-scale area-based mappingwith the most commonly used technique to measure SWE being passive microwave, which is limited to coarse spatial resolutions of 25 km orgreater and to areas without significant topographic variation. Passive microwave also has a negative bias for large SWE. Another method isrepeat-pass synthetic aperture radar interferometry (InSAR) that allows measurement of SWE change at much higher spatial resolution. However, ithas not been widely adopted because (1) the phase unwrapping problem has not been robustly addressed, especially for interferograms with poorcoherence, and (2) SWE change maps scaled directly from repeat-pass interferograms are not an absolute measurement but contain unknown offsets foreach contiguous coherent area. We develop and test a novel method for repeat-pass InSAR-based dry-snow SWE estimation that exploits the sensitivityof the dry-snow refraction-induced InSAR phase to topographic variations. The method robustly estimates absolute SWE change at spatial resolutionsof < 1 km without the need for phase unwrapping. We derive a quantitative signal model for this new SWE change estimator and identifythe relevant sources of bias. The method is demonstrated using both simulated SWE distributions and a 9-year RADARSAT-2 (C-band,5.405 GHz) spotlight-mode dataset near Inuvik, Northwest Territories (NWT), Canada. SWE results are compared to in situ snow survey measurements and estimates fromERA5 reanalysis. Our method performs well in high-relief areas, thus providing complementary coverage to passive-microwave-based SWEestimation. Further, our method has the advantage of requiring only a single wavelength band and thus can utilize existing spaceborne syntheticaperture radar systems.