Abstract
Abstract. Snow surface temperature is a key control on and result of dynamically coupled energy exchanges at the snow surface. The snow surface temperature is the result of the balance between external forcing (incoming radiation) and energy exchanges above the surface that depend on surface temperature (outgoing longwave radiation and turbulent fluxes) and the transport of energy into the snow by conduction and meltwater influx. Because of the strong insulating properties of snow, thermal gradients in snow packs are large and nonlinear, a fact that has led many to advocate multiple layer snowmelt models over single layer models. In an effort to keep snowmelt modeling simple and parsimonious, the Utah Energy Balance (UEB) snowmelt model used only one layer but allowed the snow surface temperature to be different from the snow average temperature by using an equilibrium gradient parameterization based on the surface energy balance. Although this procedure was considered an improvement over the ordinary single layer snowmelt models, it still resulted in discrepancies between modeled and measured snowpack energy contents. In this paper we evaluate the equilibrium gradient approach, the force-restore approach, and a modified force-restore approach when they are integrated as part of a complete energy and mass balance snowmelt model. The force-restore and modified force-restore approaches have not been incorporated into the UEB in early versions, even though Luce and Tartoton have done work in calculating the energy components using these approaches. In addition, we evaluate a scheme for representing the penetration of a refreezing front in cold periods following melt. We introduce a method to adjust effective conductivity to account for the presence of ground near to a shallow snow surface. These parameterizations were tested against data from the Central Sierra Snow Laboratory, CA, Utah State University experimental farm, UT, and subnivean snow laboratory at Niwot Ridge, CO. These tests compare modeled and measured snow surface temperature, snow energy content, snow water equivalent, and snowmelt outflow. We found that with these refinements the model is able to better represent the snowpack energy balance and internal energy content while still retaining a parsimonious one layer format.
Highlights
Snowmelt is an important source of water in the western United States and much of the world
There is no one right solution and in this paper we examine and evaluate single layer solutions that avoid some of the complexity of multilayer models for our purposes, which are the quantification of overall surface energy exchanges and meltwater produced by a snowmelt model for hydrological studies
The new surface Utah Energy Balance (UEB) model with the modified force-restore surface temperature parameterization was calibrated against the data from the Utah State University drainage farm (USUDF) to adjust some parameters and reflect the model changes
Summary
Snowmelt is an important source of water in the western United States and much of the world. Modeling snowmelt is important for water resource management and the assessment of spring snowmelt flood risk. The processes involved in snowmelt have been widely described (US Army Corps of Engineers, 1956; Gray and Male, 1981; Bras, 1990; Dingman, 1994; Linsley et al, 1975; Viessman et al, 2002). The heat flux between the snowpack and the atmosphere is partially governed by the snow surface temperature (Gray and Male, 1981; Dingman, 1994; Dozier, 1989) which depends on the conductive heat flux into the snow. One of the primary reasons for the poor performance of single layer models in comparative validations is the poor representation of internal snowpack heat transfer processes
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