Date of this Version
The water supply in the western United States is in large part derived from runoff originating from mountain snowpacks. Temperature and precipitation control snowpack growth, both which are sensitive to climate change. This study uses daily snow telemetry (SNOTEL) observations and reanalysis-based cyclone center locations and pressures to correlate snowpack changes with cyclone activity. The results indicate that while a quarter of the stations used in this study indicate significant shifts toward lower peak snow water equivalent (SWE) amounts, the snowpack conditions differ between regions. Stations in the Utah region experience earlier peak SWE dates, shorter accumulation seasons, and fewer total snowcover days, indicating delayed snowpack initiation and multiple melt events. Other regions, such as the Middle and Southern Rockies, do not show changes toward less continuous snowcover, yet have lower peak SWE amounts. Unlike previous studies, only 5% of the stations indicate significant shifts toward shorter melt seasons. The direct effects of increasing temperatures does impact the type of precipitation events and the initiation of snowpack accumulation However, the indirect effects related to the timing and amount of precipitation events, in connection to the frequency and intensity of winter storms, are also critical. Variations in cyclone activity, occurring at the beginning of the snow season or closer to the date of peak SWE, correspond to significant correlations of decreasing monthly precipitation totals. The likely scenario is that peak SWE amounts will decrease in the future due to increased temperatures, though altered precipitation patterns may enhance or offset SWE amount losses.
Advisor: Mark R. Anderson