ABSTRACT:

The mountains of the northeastern United States exist in a temperate, humid climate in which snowmelt dynamics remain understudied. This study evaluates spatiotemporal snowpack variability under a changing climate using a distributed, physics-based snowpack model. Here, we ran SnowModel for a montane setting surrounding Mount Mansfield, Vermont’s highest peak (1340 m). During winter precipitation events, air temperatures are often near 0°C, causing snow accumulation and melt to be highly sensitive to model parameterizations, elevation, and shifting temperatures. Tests of various model formulations showed that a wet bulb temperature threshold for precipitation phase partitioning and gravity-dominated liquid water percolation reduced model error most effectively in this unique snowpack and climate. Using the optimized model framework, the average percent bias of snow depth and snow water equivalent (SWE) improved by 33% and 75%, respectively. We also assessed the effects of changing weather patterns, simulated by perturbations in temperature and precipitation model forcings. We show middle elevations (700-900 m) to be the most sensitive to these changes, with over a 70% mean decrease in SWE in the lowest temperature increase scenario. Incremental changes in temperature caused increased midwinter melt, including the emergence of new high-runoff snowmelt pulses such as one event, where a +3.3°C increase in temperature resulted in a spike of 40 mm of surface water input from the snowpack at mid-elevations. An improved knowledge of the complexity of regional snowpack heterogeneity and snowmelt dynamics is critical for understanding flood forecasting, hydrologic management, winter recreation, and ecosystem health under a changing climate.

ABSTRACT:

Observations from Mount Mansfield snow surveys conducted between 2010-2016 from UVM Snow Hydrology students. The study site for this research is Mount Mansfield, the highest peak in the Green Mountains of Vermont. Data were collected across the Ranch Brook and West Branch watersheds, which represent two high-elevation headwaters catchments.

ABSTRACT:

The Summit-to-Shore cold weather observational network aims to capture the high-resolution spatial heterogeneity of snowpack and meteorological variables across an elevational transect of Vermont. Traditional meteorological measurements such as air temperature, relative humidity, wind speed and direction, net radiation; soil measurements such as soil heat flux, soil temperature, and moisture; and snowpack measurements such as snow water equivalent (SWE) and snow depth are measured across this transect. Stations span a range of landscape characteristics. Sites are located in the low elevations of the Champlain Valley on the shore of Lake Champlain, to mid-elevation sites in the Champlain Valley in the foothills of the Green Mountains, to the Mount Mansfield region at high elevations, to the Sleeper’s River Research Watershed in the eastern part of the state. Sites surrounding Mount Mansfield are mostly concentrated to the Ranch Brook watershed, which is a location of a long-term streamflow record as well as some historical snow surveys. Stations surrounding Mount Mansfield capture varying slope aspects, forest canopy types, elevations, as well as both the eastern and western slopes of the Mount Mansfield ridgeline. By using data from this observational network, we hope to characterize snowpack evolution in response to varying forest cover, topography, and thermodynamic drivers. These measurements will also provide high resolution data as validation for computational snowpack models. This will help augment research in a unique climate and snowpack that is relatively understudied with respect to snow research.