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Title: The sensitivity of modeled snow accumulation and melt to precipitation phase methods across a climatic gradient
Abstract. A critical component of hydrologic modeling in cold andtemperate regions is partitioning precipitation into snow and rain, yetlittle is known about how uncertainty in precipitation phase propagates intovariability in simulated snow accumulation and melt. Given the wide varietyof methods for distinguishing between snow and rain, it is imperative toevaluate the sensitivity of snowpack model output to precipitation phasedetermination methods, especially considering the potential of snow-to-rainshifts associated with climate warming to fundamentally change the hydrologyof snow-dominated areas. To address these needs we quantified thesensitivity of simulated snow accumulation and melt to rain–snowpartitioning methods at sites in the western United States using theSNOWPACK model without the canopy module activated. The methods in thisstudy included different permutations of air, wet bulb and dew pointtemperature thresholds, air temperature ranges, and binary logisticregression models. Compared to observations of snow depth and snow water equivalent (SWE), thebinary logistic regression models produced the lowest mean biases, whilehigh and low air temperature thresholds tended to overpredict andunderpredict snow accumulation, respectively. Relative differences betweenthe minimum and maximum annual snowfall fractions predicted by the differentmethods sometimes exceeded 100 % at elevations less than 2000 m in theOregon Cascades and California's Sierra Nevada. This led to rangesin annual peak SWE typically greater more » than 200 mm,exceeding 400 mm in certain years. At the warmer sites, ranges in snowmelttiming predicted by the different methods were generally larger than 2 weeks, while ranges in snow cover duration approached 1 month and greater.Conversely, the three coldest sites in this work were relatively insensitiveto the choice of a precipitation phase method, with average ranges in annualsnowfall fraction, peak SWE, snowmelt timing, and snow cover duration of lessthan 18 %, 62 mm, 10 d, and 15 d, respectively. Average ranges in snowmeltrate were typically less than 4 mm d−1 and exhibited a smallrelationship to seasonal climate. Overall, sites with a greater proportionof precipitation falling at air temperatures between 0 and4 ∘C exhibited the greatest sensitivity to method selection,suggesting that the identification and use of an optimal precipitation phasemethod is most important at the warmer fringes of the seasonal snow zone. « less
Award ID(s):
Publication Date:
Journal Name:
Hydrology and Earth System Sciences
Page Range or eLocation-ID:
3765 to 3786
Sponsoring Org:
National Science Foundation
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