Document Type

Report

Publication Date

January 1994

Abstract

This paper describes an energy balance snowmelt model developed for the prediction of rapid snowmelt rates responsible for soil erosion and water input to a distributed water balance model. The model uses a lumped representation of the snowpack with two state variables, namely, water equivalent and energy content relative to a reference state of water in the ice phase at 0 degrees Celcius. This energy content is used to determine snowpack average temperature of liquid fraction. This representation of the snowpack is used to determine snowpack average temperature of liquid fraction. This representation of the snowpack is used in a distributed version of the model with each of these state variables modeled at each point on a rectangular grid corresponding to a digital elevation model. Inputs are air temperature, precipitation, wind speed, humidity and radiation at hourly time steps. The model uses physically based calculations of radiative, sensible, latent and advective heat exchanges. An equilibrium parameterization of snow surface temperature accounts for differences between snow surface temperature and average snowpack temperature without having to introduce additional state variables. Melt outlfow is a function of the liquid fraction, using Darcy's law. This allows the model to account for continued outlflow even when the energy balance is negative. A detailed description of the model is given together with results of tests of individual components and the complete model against data collected at the Central Sierra Snow Laboratory, California; Reynolds Creek Experimental Watershed, Boise Idaho; and at the Utah State University drainage research farm, Logan Utah. The testing includes comparisons against melt outflow collected in lysimeters and melt collectors, surface snow temperatures collected using infrared temperature sensors and depth and water equivalent measured using snow core samplers.

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