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United States Department of Agriculture

Agricultural Research Service

Title: Snowmelt Simulation with the Simultaneous Heat and Water (Shaw) Model

Authors
item Flerchinger, Gerald
item Cooley, Keith

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 1998
Publication Date: N/A

Technical Abstract: The modeling approach and simulation results of the Simultaneous Heat and Water (SHAW) model are presented. The SHAW model is a detailed process model of heat, water and solute movement in a plant-snow-residue-soil system, capable of simulating the effect of climate, slope, vegetation cover, and management effects on near-surface conditions. Unique features of the SHAW model include detailed provisions for soil freezing and thawing and a detailed approach for simulating transpiration and heat transfer through a multi-species plant canopy. Within the model, a complete energy balance of a multi-layered snowpack is computed on a daily or hourly time step. Energy terms include solar and long-wave radiation exchange, sensible and latent heat transfer at the surface, and vapor transfer within the snowpack. Absorbed solar radiation, corrected for local slope, is based on measured incoming solar radiation, with albedo estimated dfrom grain size, which in turn is estimated from snow density. Long-wave radiation emitted by the atmosphere is estimated from the Stefan-Boltzmana law and adjusted for cloud cover (estimated from measured solar radiation). Surface sensible and latent heat transfers are estimated using a bulk aerodynamic approach with stability corrections. The SHAW model additionally includes the effect of vegetation and a detailed energy balance of residue and soil beneath the snow cover. Snowmelt simulation with the SHAW model was tested by applying the model to two years of data at three sites ranging from shallow (<0.1m) snow cover on a west-facing slope to a deep (2m) snow drift on a north-facing slope. Snow depth, density, and the magnitude and timing of snow cover outflow were accurately simulated for all sites.

Last Modified: 11/24/2014
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