Are Temperature-Index Models Appropriate for Assessing Climate Change Impacts On Snowmelt

TitleAre Temperature-Index Models Appropriate for Assessing Climate Change Impacts On Snowmelt
Publication TypeConference Proceedings
Year of Conference2014
AuthorsRaleigh, Mark S., and Clark Martyn P.
Conference Name82nd Annual Western Snow Conference
Series TitleProceedings of the Western Snow Conference
Date Published2014
Conference LocationDurango, Colorado
Keywordsclimate change, Energy balance, physically-based model, temperature-index model

Robust projections of climate change impacts are critical for natural resource planning in snow-dominated watersheds. Numerous studies have applied temperature-index (TI) snow models using calibrated parameter sets from the historic period, and estimate climate change impacts by forcing TI snow models with different climate scenarios. However, this methodology is questionable because (1) it assumes stationarity in model parameters, (2) it assumes the climate change signal is embedded in temperature alone, and (3) it does not account for changes in the snowmelt energy balance in a warmer climate. Here we explore the relationships between TI melt factors and changes in climate to understand the reliability of TI models for quantifying climate change impacts on snow hydrology. We examine historic relationships between temperature and melt factors (derived from observations) at 510 SNOTEL sites across diverse hydroclimates. Results show that melt factors decrease with increasing mean annual temperature at 98.6% of the sites (76% with statistical significance), and decrease with declining peak SWE and earlier peak SWE timing at over 90% of the sites. The results imply that historically calibrated TI models will overestimate snowmelt rates when applied in a warmer climate, and therefore their usage in climate change studies is problematic.