Snow water equivalent retrieval over Idaho – Part 2: Using L-band UAVSAR repeat-pass interferometry

• Published in: The Cryosphere
• Main Authors: Z. Hoppinen, S. Oveisgharan, H.-P. Marshall, R. Mower, K. Elder, C. Vuyovich
• 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-18-575-2024; https://doaj.org/article/5f686407e0d9413fbe70d3f23dcdeb03

This study evaluates using interferometry on low-frequency synthetic aperture radar (SAR) images to monitor snow water equivalent (SWE) over seasonal and synoptic scales. We retrieved SWE changes from nine pairs of SAR images, mean 8 d temporal baseline, captured by an L-band aerial platform, NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), over central Idaho as part of the NASA SnowEx 2020 and 2021 campaigns. The retrieved SWE changes were compared against coincident in situ measurements (SNOTEL and snow pits from the SnowEx field campaign) and to 100 m gridded SnowModel modeled SWE changes. The comparison of in situ to retrieved measurements shows a strong Pearson correlation ( R =0.80 ) and low RMSE (0.1 m, n =64 ) for snow depth change and similar results for SWE change (RMSE = 0.04 m, R =0.52 , n =57 ). The comparison between retrieved SWE changes to SnowModel SWE change also showed good correlation ( R =0.60 , RMSD = 0.023 m, n = 3.2 × 10 6 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="ff50d2012987d1562d71d16b09a6e75c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-18-575-2024-ie00001.svg" width="64pt" height="14pt" src="tc-18-575-2024-ie00001.png"/></svg:svg> ) and especially high correlation for a subset of pixels with no modeled melt and low tree coverage ( R =0.72 , RMSD = 0.013 m, n = 6.5 × 10 4 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="94880f843809c791a391af0776299e29"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-18-575-2024-ie00002.svg" width="64pt" height="14pt" src="tc-18-575-2024-ie00002.png"/></svg:svg> ). Finally, we bin the retrievals for a variety of factors and show decreasing correlation between the modeled and retrieved values for lower elevations, higher incidence angles, higher tree percentages and heights, and greater cumulative ...