Detre et al. (2025) Sentinel‐1 SAR Estimates of Snowmelt Onset Coincide With SNOTEL Soil Moisture Pulses Across the Western United States

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Hydrological Processes
• Year: 2025
• Date: 2025-11-27
• Authors: Ally Detre, Daniel McGrath, Eric Gagliano, Randall Bonnell, Ryan Webb, Hans‐Peter Marshall, David Shean
• DOI: 10.1002/hyp.70341

Research Groups

Not explicitly mentioned in the abstract.

Short Summary

This study investigated snowpack conditions around Sentinel-1 SAR-derived snowmelt runoff onset and evaluated these estimates against SNOTEL soil moisture pulses, finding that SAR-derived onset corresponds to increasing liquid water content but can differ temporally from in-situ melt signals due to local climatological conditions.

Objective

• To assess the snowpack state prior to and after Sentinel-1 SAR-derived runoff onset estimates.
• To evaluate Sentinel-1 SAR estimates of runoff onset with SNOTEL-derived estimates of melt output via soil moisture ‘pulses’.

Study Configuration

• Spatial Scale: Five field sites (locations not specified, but within the Western United States context) and 260 SNOw TELemetry (SNOTEL) stations across the Western United States.
• Temporal Scale: Seasonal snowmelt period, with repeat field measurements and time-series analysis of Sentinel-1 SAR backscatter and SNOTEL data.

Methodology and Data

• Models used: Sentinel-1 SAR backscatter time-series analysis for identifying snowmelt runoff onset (based on seasonal minimum backscatter).
• Data sources:
  • Repeat field measurements at five sites: Snow pit measurements for liquid water content (LWC) and snowpack temperature (isothermality).
  • SNOTEL station data (n = 260): Soil moisture, peak snow water equivalent (SWE), and positive degree days.
  • Sentinel-1 Synthetic Aperture Radar (SAR): Satellite imagery used to derive snowmelt runoff onset estimates.

Main Results

• On the date of minimum backscatter (Sentinel-1 SAR-derived runoff onset):
  • The snowpack was isothermal at three of the five field sites.
  • Snow pit-measured LWC was increasing at all five field sites relative to previous survey dates.
• SNOTEL soil moisture pulses:
  • Preceded Sentinel-1 SAR estimates of snowmelt runoff onset by a median of 3 days (standard deviation = ±25.3 days).
  • Post-dated peak SWE by a median of 3 days (standard deviation = ±18.2 days).
• Snow density and the number of positive degree days on the soil moisture pulse date:
  • Increased with latitude and longitude.
  • Decreased with elevation.
• Local climatological conditions exert significant influence on meltwater runoff onset signal clarity for both in situ and satellite-based estimates.

Contributions

• Provides detailed investigations into the snowpack state (e.g., LWC, isothermality) before and after Sentinel-1 SAR-derived snowmelt runoff onset, addressing a previously identified knowledge gap.
• Evaluates the accuracy and timing of satellite-based snowmelt runoff onset estimates against a large network of in-situ SNOTEL soil moisture data across a broad region.
• Quantifies the temporal offset between SAR-derived and SNOTEL-derived melt signals, offering insights into their agreement and discrepancies.
• Highlights the significant influence of local climatological conditions (latitude, longitude, elevation) on the clarity and timing of meltwater runoff onset signals from both in-situ and satellite observations.

Funding

Not mentioned in the abstract.

Citation

@article{Detre2025Sentinel1,
  author = {Detre, Ally and McGrath, Daniel and Gagliano, Eric and Bonnell, Randall and Webb, Ryan and Marshall, Hans‐Peter and Shean, David},
  title = {Sentinel‐1 <scp>SAR</scp> Estimates of Snowmelt Onset Coincide With <scp>SNOTEL</scp> Soil Moisture Pulses Across the Western United States},
  journal = {Hydrological Processes},
  year = {2025},
  doi = {10.1002/hyp.70341},
  url = {https://doi.org/10.1002/hyp.70341}
}