Location: Northwest Watershed Management Research
Title: Estimating surface sublimation losses from the snowcover in a mountain catchment using eddy covariance and turbulent transfer calculations Authors
Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2011
Publication Date: November 29, 2012
Citation: Reba, M.L., Pomeroy, J., Marks, D.G., Link, T. 2012. Estimating surface sublimation losses from the snowcover in a mountain catchment using eddy covariance and turbulent transfer calculations. Hydrological Processes. 26:3699-3711. Interpretive Summary: Measured sublimation using eddy covariance for three snow seasons at two contrasting sites yielded results that provide valuable information for the water balance of snow dominated semi-arid mountain watershed and can also be used for evaluating the effect of land use on hydrology and for hydrological model testing. Comparing measured sublimation between two sites supports the idea that sites well exposed to wind yield larger sublimation rates and total sublimation over a season than do sheltered sites. Mean sublimation rates were 0.39 mm d-1 and 0.15 mm d-1 at the exposed and sheltered site, respectively and sublimation rates increased as the season progressed from low energetics in winter to high energetics in spring. Sublimation from snow accounted for 12% of maximum snow accumulation at the exposed site and 2.2% of maximum snow accumulation at the sheltered site. As sublimation from snow is difficult to measure and often a neglected component of the water balance, the findings in this study better define the magnitude and variation of this term. The measured sublimation values, trends, and comparisons from two contrasting sites can be used as a guide for modelers and researchers.
Technical Abstract: Sublimation is a critical component of the snow cover mass balance. While sublimation can be directly measured using eddy covariance (EC), such measurements are relatively uncommon in complex mountainous environments. EC measurements of surface snowpack sublimation from three consecutive winter seasons (2004, 2005 and 2006) at a wind-exposed and wind-sheltered site were analyzed to characterize sublimation in mountainous terrain. During the 2006 snow season, snow surface and near-surface air temperature, humidity and wind were also measured, permitting the calculation of sublimation rates and a comparison with EC observations. This comparison showed that measured and simulated sublimation was very similar at the exposed site, but less so at the sheltered site. Wind speeds at the exposed site were nearly four times that at the sheltered site, and the exposed site yielded measured sublimation that was two times the magnitude of that at the sheltered site. Time variation of measured sublimation showed diurnal increases in the early afternoon and increased rates as the snow season progressed. Measured mean daily sublimation rates were 0.39 mm day-1 and 0.15 mm day-1 at the exposed and sheltered site, respectively. Measured seasonal sublimation as a percent of the maximum snow water equivalent at the sheltered site was approximately 4% in 2004 and 2006 and 8% in 2005. At the exposed site, measured sublimation accounted for 16% and 41% of the maximum snow accumulation in 2006 and 2005, respectively. Simulated sublimation was only available for 2006 and suggested smaller but comparable percentages to the sublimation estimated from observations. At the exposed site, a total of 42 mm were sublimated for the snow season which constituted 12% of the maximum accumulation. At the sheltered site, 17 mm (2.2% of maximum accumulation) was sublimated over the snow season.