Long-term snow distribution observations in a mountain catchment: Assessing variability, time stability, and the representativeness of an index site

This study presents an analysis of snow distribution heterogeneity and the factors affecting this variability. The analysis focuses on manually sampled data from 21 snow surveys covering 11 years at the drift-dominated Reynolds Mountain East catchment (0.36 km(2)) in southwestern Idaho, USA. Surveys were conducted midwinter and in early spring. Interseason and intraseason trends were examined along with the time stability of distributions, goodness-of-fit to theoretical distributions, and the representativeness of an index site as a measure of basin-wide snow water equivalent. The average snow depth coefficient of variation (CV) over the entire time period was 0.71, which is in accordance with broad regional assessments. Higher wind speeds during snow events and increased melt led to increased heterogeneity and higher CVs. Forested sites produced lower CVs presumably due to moderated winds at these sites. Consistent wind directions produced accumulation patterns that were very stable from year-to-year. Many previous studies have suggested that vital subgrid snow heterogeneity in large-scale models can be approximated with parametric distributions. Gamma distributions were preferred over lognormal distributions in describing the overall distribution while in tree-covered regions with less variability there was little difference between the two. It was also found that an index site, akin to the majority of North American mountain weather observation stations, provided a reasonable approximation of catchment-averaged SWE in most years. However, the reliability of this measure decreased in years that deviated from normal patterns.