Location: Northwest Watershed Management Research
Title: Sensitivity of the snowcover energetics in a mountain basin to variations in climate Authors
Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2011
Publication Date: October 15, 2011
Repository URL: http://onlinelibrary.wiley.com/doi/10.1002/hyp.8155/abstract
Citation: Reba, M.L., Marks, D.G., Winstral, A.H., Link, T.E., Kumar, M. 2011. Sensitivity of the snowcover energetics in a mountain basin to variations in climate. Hydrological Processes. 25(21):3312-3321. Interpretive Summary: This paper presents simulated model results for the seasonal snowcover in a small mountain basin from 1984 to 2008. The study site was located within Reynolds Creek Experimental Watershed. The primary objective of the study was to test the sensitivity of the snowcover to variations in climate. Isnobal, a two-layer snowcover mass and energy balance model, was used to analyze the sensitivity. Each of the 25 study years was grouped into categories based on snow season meteorological conditions. The simulated basin average precipitation, snow water equivalent (SWE), surface water input (SWI) and sublimation and measured stream discharge at the outlet were used to determine sensitivity. The meteorological condition influenced the timing and magnitude of SWE, SWI and measured discharge. There was little difference in simulated cumulative sublimation, though substantial differences were found in the percent of peak SWE that was lost due to sublimation. The energy balance approach to seasonal snowcover modeling, Isnobal, was shown to be accurate under the varied meteorological conditions that occurred during the 25 water years simulated. Based on these findings, the energy balance model, Isnobal, is appropriate for use in studying the influence a perturbed climate may have on the seasonal snowcover. Furthermore, it could be used to test the sensitivity of snowcover development under modified climate conditions. The form and timing of precipitation influenced accumulation and melt markedly. Warm winters, characterized by mid- and early-winter rain, resulted in earlier SWI and stream discharge when compared to cool winters. Cool conditions delayed the generation of SWI and stream discharge. Warmer conditions produced more SWE and SWI during the winter, shortened the melt season and would be expected to extend the summer drought.
Technical Abstract: Snow is an important natural reservoir that holds water on the landscape for release later in the season in western North America and other portions of the world. As air temperature increases with global climate change, the character of the generally established seasonal snowcover will be affected. In order to study the specific response to variable climate a carefully collected and processed meteorological dataset for the 1984-2008 water years was assembled for a snow-dominated headwater catchment. The data are used to force a physically-based, distributed energy balance snow model to simulate patterns of snow deposition and melt over the catchment for the 25-year period. This period covers both the highest (1984) and lowest (1992) snow seasons on record and exhibits extreme inter-annual variability. This unique forcing dataset captured meteorological conditions that resulted in the range of variability in snowcover accumulation, timing of ablation, and the timing and amount of surface water input (SWI) and discharge during the 25-year study period. SWI is the amount of liquid water delivered to the soil surface from melting snow or from rain that passes through the snowcover or falls directly on the soil. Warm winters, characterized by early- and mid-winter rain, triggered earlier inputs from surface water input and response in discharge than cool winters. Cool conditions prolonged the generation of surface water input and streamflow out of the basin. Warmer conditions produced more snow water equivalent and SWI during the winter, shortened the melt season and would be expected to extend the summer drought.