DOI: 10.5061/dryad.bvq83bkm9
title: Site characteristics: Soil moisture summary for 376 SNOTEL station locations

description: Satellite-based synthetic aperture radar (SAR) has been used to assess and
 quantify snowmelt across large spatial and temporal scales. While there
 have been recent advancements in SAR-based snow water equivalent (SWE)
 retrieval methods, obtaining accurate estimates of SWE requires knowledge
 of the amount of liquid water content in the snowpack given its strong
 impact on radar velocity. Recent studies have utilized Sentinel-1 SAR to
 identify snowmelt runoff onset in complex, high-elevation terrain based on
 a seasonal minimum backscatter time-series, however, detailed
 investigations into the snowpack state before and after snowmelt runoff
 onset are lacking. In this study, we integrated repeat field measurements,
 SNOw TELemetry (SNOTEL) station data (n = 260) from across the western
 U.S., and paired Sentinel-1 SAR estimates of snowmelt runoff onset to 1)
 assess the snowpack state prior to and after Sentinel-1 SAR-derived runoff
 onset estimates, and 2) evaluate Sentinel-1 SAR estimates of runoff onset
 with SNOTEL-derived estimates of melt output via soil moisture “pulses”.
 We found that SNOTEL soil moisture pulses preceded Sentinel-1 SAR
 estimates of snowmelt runoff onset by a median of 3 days (standard
 deviation = ± 25.3 days) and post-dated peak SWE by a median of 3 days
 (standard deviation = ± 18.2 days). Soil moisture pulse dates occurred
 earliest in montane forests/prairie snowpacks and latest in maritime
 snowpacks. Snow density and number of positive degree days on soil
 moisture pulse date increased with latitude and longitude and decreased
 with elevation. While satellite-based estimates of snowmelt runoff onset
 provide a promising methodology for improving spaceborne retrievals of
 SWE, we emphasize the importance and influence of local climatological
 conditions on runoff onset signal clarity for both in-situ and
 satellite-based estimates.
description: # Site characteristics: Soil moisture summary for 376 SNOTEL station
 locations Dataset DOI: [10.5061/dryad.bvq83bkm9](10.5061/dryad.bvq83bkm9)
 ## Description of the data and file structure **Summary of dataset:** The
 following dataset (SNOTEL_Summary_Data.csv)  includes metadata, terrain,
 SNOTEL soil moisture, peak SWE, and Sentinel-1 SAR summary data for 376
 SNOTEL stations across the western U.S. A subset of these stations (260)
 was used in Detre et al., 2025 in a paired comparison with Sentinel-1 SAR
 estimates of snowmelt runoff onset. **Description of file structure and
 contents:** Each SNOTEL station (site_id column) included in this dataset
 contains 35 columns of summary characteristics. A subset of these stations
 (54) do not have precise coordinates, while the majority (322) have
 precise coordinates found using high-resolution optical imagery in Google
 Earth Pro in addition to the publicly available coordinates.
 **VARIABLES:** * X = Row number * state = state (two-letter abbreviation)
 where the SNOTEL station is located * site = SNOTEL station site code *
 site_name = SNOTEL station site name * site_id = unique SNOTEL station
 site code that indicates the state the station is located in, and its site
 code (i.e., CO_531 is located in Colorado and has site code 531) *
 snotel_start_date = first date that SNOTEL station began reporting data *
 latitude = SNOTEL station publicly-accessible latitude (degrees) *
 latitude_precise = SNOTEL station precise latitude (degrees) found using
 high-resolution optical imagery in Google Earth Pro * longitude = SNOTEL
 station publicly-accessible longitude (degrees) * longitude_precise =
 SNOTEL station precise longitude (degrees) found using high-resolution
 optical imagery in Google Earth Pro * easting = SNOTEL station publicly
 accessible easting coordinate (meters) * easting_precise = SNOTEL station
 precise easting coordinate (meters) found using high-resolution optical
 imagery in Google Earth Pro * northing = SNOTEL station publicly
 accessible northing coordinate (meters) * northing_precise = SNOTEL
 station precise northing coordinate (meters) found using high-resolution
 optical imagery in Google Earth Pro * epsg = EPSG code * aspect = SNOTEL
 station aspect (degrees) calculated using USGS 3DEP 10 m DEM from publicly
 accessible coordinate * aspect_precise = SNOTEL station aspect (degrees)
 calculated using USGS 3DEP 10 m DEM from precise coordinate * elevation =
 SNOTEL station elevation (meters) calculated using USGS 3DEP 10 m DEM from
 publicly accessible coordinate * elevation_precise = SNOTEL station
 elevation (meters) calculated using USGS 3DEP 10 m DEM from precise
 coordinate * slope = SNOTEL station slope (degrees) calculated using USGS
 3DEP 10 m DEM from publicly accessible coordinate * slope_precise = SNOTEL
 station slope (degrees) calculated using USGS 3DEP 10 m DEM from precise
 coordinate * snowzone = Numerical values corresponding to various snow
 classifications outlined in the Global Seasonal Snow Classification,
 Version 1 dataset (Sturm & Liston, 2021) * snowzone_desc =
 Descriptions that correspond to numbered values in snowzone *
 ecoregion_l4_code = Code corresponding to various Level IV ecoregions of
 the continental United States (EPA, 2013) * ecoregion_l4_desc =
 Description corresponding to the code shown in ecoregion_l4_code *
 ecoregion_l3_code = Code corresponding to various Level III ecoregions of
 the continental United States (EPA, 2013) * ecoregion_l3_desc =
 Description corresponding to the code shown in ecoregion_l3_code *
 median_sm_doy = Median soil moisture pulse DOY * count_grade_1 = Number of
 Grade 1 soil moisture pulses * count_grade_2 = Number of Grade 2 soil
 moisture pulses * percent_grade_1 = Percent Grade 1 soil moisture pulses
 (out of total pulses for this station) * percent_grade_2 = Percent Grade 2
 soil moisture pulses (out of total pulses for this station) *
 total_years_smdata = Number of valid soil moisture pulses/years of soil
 moisture data * median_peakswe_doy = Median peak SWE DOY *
 distance_sm_peakswe = Distance (days) between median soil moisture pulse
 DOY and median peak SWE DOY. Negative difference (days) indicates the soil
 moisture pulse precedes peak SWE, while positive difference (days)
 indicates the soil moisture pulse post-dates peak SWE * s1_valid_years =
 Number of valid Sentinel-1 SAR estimates of snowmelt runoff onset that
 correspond with SNOTEL soil moisture pulse pairs. Stations that do not
 have Sentinel-1 SAR paired data will be indicated by “NA”
 **ABBREVIATIONS** * DOY = Day of year * Sm = soil moisture pulse * Peakswe
 = SNOTEL peak SWE * S1 = Sentinel-1 SAR **MISSING VALUES** * Missing
 values are indicated with “NA” ## Code/software The spreadsheet is in CSV
 format and thus is designed to be easily opened and read across various
 platforms and applications (e.g., Microsoft Excel, Google Sheets, Apple
 Numbers, etc.) ## Access information **Other sources the data was derived
 from:** * Github snotelprocessr (Detre, 2025) script for extracting soil
 moisture pulse date from SNOTEL station data *
 [https://github.com/allydetre/snotelprocessr](https://github.com/allydetre/snotelprocessr) * NRCS SNOTEL station data repository * USDA NRCS. (2024). SNOwpack TELemetry Network (SNOTEL) [Dataset]. USDA NRCS. Retrieved from [https://catalog.data.gov/dataset/snowpack-telemetry-network-snotel](https://catalog.data.gov/dataset/snowpack-telemetry-network-snotel) * EPA ecoregions * U.S. Environmental Protection Agency. (2013). *Level III ecoregions of the conterminous United States* [Data set]. U.S. EPA Office of Research and Development, National Health and Environmental Effects Research Laboratory. Retrieved from [https://www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states](https://www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states) * Sturm and Liston Global Seasonal Snow Classification * Liston, G. E. and M. Sturm. 2021. Global Seasonal-Snow Classification, Version 1. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. [https://doi.org/10.5067/99FTCYYYLAQ0](https://doi.org/10.5067/99FTCYYYLAQ0).