Evaporation from Snow in the Central Sierra Nevada of California

Abstract

Evaporation from snow was calculated with the mean-profile method using single-level meteorological data at eight locations representing a variety of alpine and sub-alpine terrain in the central Sierra Nevada, California. Four to six years of data were analyzed at most of the sites. Evaporation from snow was highest in mid-winter, when the vapor pressure gradient between the snow surface and the air was at its maximum, and declined throughout the snowmelt season. Near the end of snowmelt, condensation of water vapor on the snow surface often matched or exceeded evaporative loss. Annual evaporation from the snowpack varied from 12 to 156 mm. We estimate mean annual regional evaporation in the sub-alpine and alpine zones (excluding evaporation from tree-captured snow and during wind re-deposition) as 80 to 100 mm, approximately 7 per cent of the maximum accumulation during an average snow year. Evaporation during snowmelt contributed only minor amounts to the total seasonal loss, typically around 25 mm, or about 2% of the maximum average accumulation.