loading page

Challenges and Capabilities in Estimating Snow Mass Intercepted in Conifer Canopies with Tree Sway Monitoring
  • +3
  • Mark S. Raleigh,
  • Ethan D. Gutmann,
  • John T Van Stan,
  • Sean P. Burns,
  • Peter D Blanken,
  • Eric E. Small
Mark S. Raleigh
Oregon State University, Oregon State University

Corresponding Author:raleigma@oregonstate.edu

Author Profile
Ethan D. Gutmann
National Center for Atmospheric Research (UCAR), National Center for Atmospheric Research (UCAR)
Author Profile
John T Van Stan
Georgia Southern University, Georgia Southern University
Author Profile
Sean P. Burns
University of Colorado Boulder, University of Colorado Boulder
Author Profile
Peter D Blanken
University of Colorado Boulder, University of Colorado Boulder
Author Profile
Eric E. Small
University of Colorado Boulder, University of Colorado Boulder
Author Profile


Snowpack accumulation in forested watersheds depends on the amount of snow intercepted in the canopy and its partitioning into sublimation, unloading, and melt. A lack of canopy snow measurements limits our ability to evaluate models that simulate canopy processes and predict snowpack and water supply. Here, we tested whether monitoring changes in wind-induced tree sway can enable snow interception detection and estimation of canopy snow water equivalent (SWE). We monitored hourly tree sway across six years based on 12 Hz accelerometer observations on two subalpine conifer trees in Colorado. We developed an approach to distinguish changes in sway frequency due to thermal effects on tree rigidity versus intercepted snow mass. Over 60% of days with canopy snow had a sway signal in the range of possible thermal effects. However, when tree sway decreased outside the range of thermal effects, canopy snow was present 93-95% of the time, as confirmed with classifications of PhenoCam imagery. Using sway tests, we converted significant changes in sway to canopy SWE, which was correlated with total snowstorm amounts from a nearby SNOTEL site (Spearman r=0.72 to 0.80, p<0.001). Greater canopy SWE was associated with storm temperatures between -7°C and 0°C and wind speeds less than 4 m/s. Lower canopy SWE prevailed in storms with lower temperatures and higher wind speeds. We conclude that monitoring tree sway is a viable approach for quantifying canopy SWE, but challenges remain in converting changes in sway to mass and further distinguishing thermal and mass effects on tree sway.
Mar 2022Published in Water Resources Research volume 58 issue 3. 10.1029/2021WR030972