Analysis of snowpack dynamics during the spring melt season for a sub-alpine site using point measurements and numerical modeling

Snowpack dynamics through October 2014-June 2017 were described for a forested, sub-alpine field site in southeastern Wyoming. Point measurements of wetness and density were combined with numerical modeling and continuous time series of snow depth, snow temperature, and snowpack outflow to identify 5 major classes of distinct snowpack conditions. Class (i) is characterized by no snowpack outflow and variable average snowpack temperature and density. Class (ii) is characterized by short durations of liquid water in the upper snowpack, snowpack outflow values of 0.0008-0.005cm hr(-1), an increase in snowpack temperature, and average snow density between 0.25-0.35g cm(-3). Class (iii) is characterized by a partially saturated wetness profile, snowpack outflow values of 0.005-0.25cm hr(-1), snowpack temperature near 0 degrees C, and average snow density between 0.25-0.40g cm(-3). Class (iv) is characterized by strong diurnal snowpack outflow pattern with values as high as 0.75cm hr(-1), stable snowpack temperature near 0 degrees C, and stable average snow density between 0.35-0.45g cm(-3). Class (v) occurs intermittently between Classes (ii)-(iv) and displays low snowpack outflow values between 0.0008-0.04cm hr(-1), a slight decrease in temperature relative to the preceding class, and similar densities to the preceding class. Numerical modeling of snowpack properties with SNOWPACK using both the Storage Threshold scheme and Richards' equation was used to quantify the effect of snowpack capillarity on predictions of snowpack outflow and other snowpack properties. Results indicate that both simulations are able to predict snow depth, snow temperature, and snow density reasonably well with little difference between the 2 water transport schemes. Richards' equation more accurately simulates the timing of snowpack outflow over the Storage Threshold scheme, especially early in the melt season and at diurnal timescales.