WINDBLOWN SNOW BEDFORMS AND THEIR IMPACTS ON SNOW WATER EQUIVALENCY, ON TRONSEN RIDGE, WENATCHEE RANGE, WASHINGTON

Windblown snow bedforms (WBSBF) are formations of distinct sizes, shapes, and patterns, resulting from the interaction of wind and snow particles. In mid-latitude mountains, the life cycles and effects of WBSBF on surface roughness and water storage are not well understood. This is due to the extreme nature of the formation of WBSBF, which occur in remote high elevation mountain environments during severe weather events, making it difficult to study these dramatic formations in real time and predict their occurrence with any regularity. WBSBF result in a snow surface that is extremely variable making it difficult to accurately predict the amount of water stored in the snowpack through snow water equivalency (SWE) models. The purpose of this research was to: 1) establish methods to actively monitor WBSBF in real time; 2) improve the understanding of life cycles of WBSBF in the Cascade Mountains; and 3) create a predictive model to not only identify WBSBF occurrence but use that model to improve the inputs for SWE modeling and understand how they affect water content in the snowpack. Time lapse photos and real time weather data were collected in Tronsen Basin in the Eastern Cascades, WA through two winter seasons. The observed WBSBF were divided into 4 classifications (new snow, dunes, sastrugi, and other), with 12 measured weather, vegetation, and topographic controls on their formation including windspeed, wind direction, temperature, slope angle, aspect, and vegetation type and size. Photos taken with time-lapse cameras on site showed WBSBF in Tronsen Basin follow a distinct life cycle, consisting of new snow, WBSBF growth and snow movement into dunes, followed by sintering of the old snow causing sastrugi, which are then covered by new snow or hardened further by rain followed by refreezing. Interactions between windblown snow and the variations in mountain topography, vegetation, and climate cause WBSBF to be locked in place for the season, causing continual compaction of the WBSBF. This increases the density and rate of sintering, which is unlike WBSBF in the plains, where these formations are constantly growing and being destroyed. A logistic model using the photographic data combined with accurate real time weather data, will allow for the prediction of WBSBF, which can be used to improve the inputs for SWE calculations.