C002-0010
Which Family Trees of Snow Interception Modeling History have the Essentials for Success?

Monday, 7 December 2020
Poster
Jessica D Lundquist, University of Washington, Civil and Environmental Engineering, Seattle, WA, United States, Susan E. Dickerson-Lange, University of Washington, Seattle, WA, United States, Ethan D Gutmann, National Center for Atmospheric Research, Boulder, CO, United States, Tobias Jonas, SLF / WSL, Davos Dorf, Switzerland, Dylan Reynolds, WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland and Cassie Lumbrazo, University of Washington Seattle Campus, Civil and Environmental Engineering, Seattle, WA, United States
Abstract:
When formulating a hydrologic model, scientists rely on parameters and parameterizations of multiple processes based on field data, but literature review suggests that more frequently people select parameterizations that were included in pre-existing models rather than directly evaluating the underlying field experiments. Problems arise when limited field data exist and when processes fundamentally change in different environments. The physics and dynamics of snow interception by conifers is just such a case. The most commonly used parameterization was based on data from four trees from one site, while the process varies dramatically between locations with relatively warmer vs. colder winters; thus field study results are not transferable between environments. Here, we combine a comprehensive literature review with a simplified model to demonstrate how a more holistic perspective should change our theory of how global models should represent snow interception. We recommend that the commonly used parameters of a fixed Imax for loading and e-folding time for unloading be abandoned and that all models include melting of in-canopy snow. We propose the following be investigated as a path forward for all models: a representation of the force balance between adhesion and cohesion vs. gravity for both interception efficiency and rates of unloading, including a) increased adhesion and cohesion as temperatures increase between -3.5 and 0°C, b) wind effects during and between storms, and c) lubrication when snow melts. For greatest impact, this framework requires dedicated field measurements across climates and forest types, and we outline priorities for which processes to study where based on how parameter sensitivity impacts the net forest effect on snow accumulation in different environments. These processes are essential for models to accurately represent the impacts of dynamically changing forest cover and snow cover on both global albedo and water supplies.
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