TY - Generic T1 - A Field Study of Snowpack Ablation at Sagehen Creek Field Station T2 - 87th Annual Western Snow Conference Y1 - 2019 A1 - Stephen Drake A1 - Holly J. Oldroyd A1 - Anne W. Nolin A1 - Alex Greenwald A1 - Sydney Weiss A1 - Keith S. Jennings A1 - Mikey Johnson A1 - Gavin R. Shields KW - ablation KW - forest KW - hydrology KW - radiation KW - snow KW - surface energy fluxes AB -

Preliminary results of a field experiment at Sagehen Creek Field Station, CA during the 2018/2019 winter season are presented. We deployed five flux towers across a subalpine forest/meadow transition zone to compare ablation processes of proximal sites. Differences in longwave and shortwave radiation, air temperature, and sublimation were observed between the five sites, varying with solar aspect, tree density, and other locale-specific parameters. Longwave exitance from snow had a sphere of influence less than 10 m whereas shortwave insolation had a range of influence up to an order of magnitude greater and depended on sun angle and tree height. Sublimation differences between sites were magnified as wind speed increased. Drifted snow caused by an isolated tree was not significant for this warm snow site.

JF - 87th Annual Western Snow Conference CY - Reno, NV UR - /files/PDFs/2019Drake.pdf ER - TY - Generic T1 - Modeling of Snowpack Accumulation and Losses in Mountainous Terrain for Both Snowpack Storage Mapping and Watershed Storage Estimates T2 - 81st Annual Western Snow Conference Y1 - 2013 A1 - Froyland, Hugo A1 - Stackhouse, Josh A1 - Schiefer, Erik A1 - Decker, Rand KW - ablation KW - accumulation KW - modeling KW - Snow water equivalent KW - snowpack KW - SWE KW - watershed AB -

A heuristic watershed-scale snowpack model that has been under development and verification at the University of Utah and now at Northern Arizona University since 1998 is now implemented on an articulate Geographic Information System (GIS) platform. Simple heuristic rules are established for the preferential accumulation and loss of snowpack in mountainous terrain. These rules include elevation and solar wattage, each at the pixel scale. The capacity for modern GIS to provide solar wattage explicitly from the root Digital Elevation Model (DEM), means that indexing this ablative potential with slope aspect and angle is no longer required. Each model run must be initialized with two snowpack Snow Water Equivalent (SWE) observations at different elevation within the watershed. One observation can be snowline. This means the model can be initialized for a water year start date, or an annual snowpack SWE maximum when it occurs, or forensic queries of historic events/years, and virtual events such as a “unit” storm or winter. Additionally, the efficiency with which a given watershed commutes water from snowpack storage to surface runoff is indexed with two different ratios; length of surface water channel in the watershed to area of the watershed, and length of watershed channel to watershed circumference. The test watersheds of Stackhouse (Rohde et al., 2012) are repeated with this model, and include four highland tributary watersheds in different physiographical provinces of the Rocky Mountains; Doyle Peak, San Francisco Peaks, Arizona; Kings Peak, Uintas, Utah; and Mt. Elbert and Jones Peak, Eastern San Juan Mountains, Colorado. These tributary sub-basins ranged in size from 88 to 210 million square meters. Snowpack accumulation and/or loss is modeled to the DEM pixel scale, in all of these cases, 30m by 30m. Snowpack SWE in storage, per pixel, is then integrated for an estimate of watershed aggregate snowpack SWE storage. As an aid in identifying watersheds that are particularly effective at snowpack SWE storage, this model allows for the comparison of SWE volumes in a given watershed to the area of the watershed; a measure of the watershed’s snow water volume to area efficiency. Another valuable data product of the model is a detailed mapping of snowpack SWE storage within the watershed at the pixel scale. This information can be used in a variety of ways. As examples of the decision support capabilities of the model, three water resource decision space challenges are investigated in an effort to demonstrate the utility of the model and include the following:

JF - 81st Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Jackson Hole, Wyoming UR - sites/westernsnowconference.org/PDFs/2013Froyland.pdf ER -