Surface air pressure also affects phase partitioning, but to a lesser degree Snowfall is more probable at a given air temperature in more arid conditions (FroidurotĮt al., 2014 Gjertsen and Ødegaard, 2005 Jennings et al., 2018b). Variability can be ascribed to relative humidity, as recent work has shown that Partitioning across large spatial extents (Raleigh and Lundquist, 2012). Threshold, or range, cannot accurately represent precipitation phase Shown to vary significantly across the Northern Hemisphere (Jennings et al., 2018b). Probability (i.e., the 50 % rain–snow air temperature threshold) has been However, the point at which the sigmoidal curve crosses 50 % snow That the probability of snowfall decreases following a sigmoidal curve asĪir temperature increases above 0 ∘C (Dai, 2008 Fassnacht et al., 2013 Kienzle,Ģ008). Temperatures at and below the freezing point (Auer,ġ974 Avanzi et al., 2014 United States Army Corps of Engineers, 1956) and Observational work has shown that precipitation is primarily solid at Logical given the strong temperature dependence of precipitation phase. The use of a spatially uniform air temperature threshold is seemingly Phase is rarely observed in mountain regions on a continuous basis over long Complicating matters is the fact that precipitation Variability in rain–snow partitioning (Jennings etĪl., 2018b Ye et al., 2013). Precipitation phase into question (Feiccabrino etĪl., 2015 Harpold et al., 2017b) because of the pronounced spatial Recent work has called this simplistic treatment of Thresholds with a linear mix of liquid and solid precipitation in between. Spatially uniform air temperature threshold or a range between two These models share is the partitioning of rainfall and snowfall based on a Models, hydrologic models, and land surface models of varying degrees ofĬomplexity (e.g., Barnett et al., 2005). How this change affects global hydroclimate, researchers have employed snow Is expected to continue with further increases in air temperature (Bintanja and Andry, 2017 Snow to rain in temperate and cold regions across the globe (e.g., Knowles et al., 2006 Trenberth, 2011), a trend that One of the most prominent impacts of climate warming has been a shift from Method is most important at the warmer fringes of the seasonal snow zone. Suggesting that the identification and use of an optimal precipitation phase Of precipitation falling at air temperatures between 0 andĤ ∘C exhibited the greatest sensitivity to method selection, Rate were typically less than 4 mm d −1 and exhibited a small Snowfall fraction, peak SWE, snowmelt timing, and snow cover duration of less To the choice of a precipitation phase method, with average ranges in annual Timing predicted by the different methods were generally larger than 2 weeks, while ranges in snow cover duration approached 1 month and greater.Ĭonversely, the three coldest sites in this work were relatively insensitive In annual peak SWE typically greater than 200 mm,Įxceeding 400 mm in certain years. Oregon Cascades and California's Sierra Nevada. Methods sometimes exceeded 100 % at elevations less than 2000 m in the The minimum and maximum annual snowfall fractions predicted by the different Underpredict snow accumulation, respectively. High and low air temperature thresholds tended to overpredict and Compared to observations of snow depth and snow water equivalent (SWE), theīinary logistic regression models produced the lowest mean biases, while Temperature thresholds, air temperature ranges, and binary logistic Study included different permutations of air, wet bulb and dew point SNOWPACK model without the canopy module activated. Partitioning methods at sites in the western United States using the Sensitivity of simulated snow accumulation and melt to rain–snow Shifts associated with climate warming to fundamentally change the hydrology Of methods for distinguishing between snow and rain, it is imperative toĮvaluate the sensitivity of snowpack model output to precipitation phaseĭetermination methods, especially considering the potential of snow-to-rain Variability in simulated snow accumulation and melt. Little is known about how uncertainty in precipitation phase propagates into Temperate regions is partitioning precipitation into snow and rain, yet A critical component of hydrologic modeling in cold and
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