Sublimation from a seasonal snowpack at a continental, mid-latitude alpine site

Abstract

Sublimation from the seasonal snowpack was calculated using the aerodynamic profile method at Niwot Ridge in the Colorado Front Range. Past studies of sublimation from snow have been inconclusive in determining both the rate and timing of the transfer of water between the snowpack and the atmosphere, primarily because they relied on one-dimensional measurements of turbulent fluxes or short term data sets. We calculated latent heat fluxes at ten minute intervals based on measurements of temperature, relative humidity and wind speed at heights of 0.5 m, 1.0 m and 2.0 m above the snowpack for nine months during the 1994- 1995 snow season. The meteorological instruments were raised or lowered daily to maintain a constant height above the snow surface. At each ten minute time step, the latent heat fluxes were converted directly into millimeters of sublimation or condensation. Total net sublimation for the snow season was 195 mm of water equivalent, or 15% of maximum snow accumulation at the stud site. The majorit y of this sublimation occurred during the snow accumulation season. Monthly losses to sublimation during the fall and winter ranged from 27 to 54 mm of water equivalent. The snowmelt season from May through mid-July showed net condensation to the snowpack ranging from 5 to 16 mm of water equivalent. Sublimation was sometimes episodic in nature, but often showed a diurnal periodicity with higher rates of sublimation during the day.