Estimating sublimation of intercepted and sub-canopy snow using eddy covariance systems

Direct measurements of winter water loss due to sublimation were made in a sub-alpine forest in the Rocky Mountains of Colorado. Above-and below-canopy eddy covariance systems indicated substantial losses of winter-season snow accumulation in the form of snowpack (0.41 mm d^-1) and intercepted snow (0.71 mm d^-1) sublimation. The partitioning between these over and under story components of water loss was highly dependent on atmospheric conditions and near-surface conditions at and below the snow/atmosphere interface. High above-canopy sensible heat fluxes lead to strong temperature gradients between vegetation and the snow-surface, driving substantial specific humidity gradients at the snow surface and high sublimation rates. Intercepted snowfall resulted in rapid response of above-canopy latent heat fluxes, high within-canopy sublimation rates (maximum = 3.7 mm d^-1), and diminished sub-canopy snowpack sublimation. These results indicate that sublimation losses from the sub-canopy snowpack are strongly dependent on the partitioning of sensible and latent heat fluxes in the canopy. This compels comprehensive studies of snow sublimation in forested regions that integrate sub-canopy and over-story processes.