Evaluating L-band InSAR snow water equivalent retrievals with repeat ground-penetrating radar and terrestrial lidar surveys in northern Colorado

• Published in: The Cryosphere
• Main Authors: R. Bonnell, D. McGrath, J. Tarricone, H.-P. Marshall, E. Bump, C. Duncan, S. Kampf, Y. Lou, A. Olsen-Mikitowicz, M. Sears, K. Williams, L. Zeller, Y. Zheng
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-18-3765-2024; https://doaj.org/article/147b04afcaab4668b469baa3bdabc705

Snow provides critical water resources for billions of people, making the remote sensing of snow water equivalent (SWE) a highly prioritized endeavor, particularly given ongoing climate change impacts. Synthetic aperture radar (SAR) is a promising method for remote sensing of SWE because radar penetrates snow, and SAR interferometry (InSAR) can be used to estimate changes in SWE ( Δ SWE) between SAR acquisitions. We calculated Δ SWE retrievals from 10 NASA L-band (1–2 GHz, ∼25 cm wavelength) uninhabited aerial vehicle SAR (UAVSAR) acquisitions covering a ∼640 km 2 swath in northern Colorado during the winters of 2020 and 2021. UAVSAR acquisitions coincided with ∼117 mm of accumulation in 2020 and ∼282 mm of accumulation in 2021. Δ SWE retrievals were evaluated against measurements of SWE from repeat ground-penetrating radar (GPR) and terrestrial lidar scans (TLSs) collected during the NASA SnowEx time series campaigns at two field sites (total area = ∼ 0.2 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="6f849f4e58925f8bb1bba366b8bd7c0c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-18-3765-2024-ie00001.svg" width="35pt" height="10pt" src="tc-18-3765-2024-ie00001.png"/></svg:svg> km 2 ) as well as SWE measurements from seven automated stations distributed throughout the UAVSAR swath. For single InSAR pairs, UAVSAR Δ SWE retrievals yielded an overall r of 0.72–0.79 and an RMSE of 19–22 mm when compared with TLS and GPR Δ SWE retrievals. UAVSAR Δ SWE showed some scatter with Δ SWE measured at automated stations for both study years, but cumulative UAVSAR SWE yielded a r of 0.92 and an RMSE of 42 mm when compared to total SWE measured by the stations. Further, UAVSAR Δ SWE RMSEs differed by <10 mm for coherences (i.e., the complex interferometric coherence) of 0.10 to 0.90, suggesting that coherence has only a small influence on the Δ SWE retrieval accuracy. Given the evaluations presented here and ...