Evaluation of alternative formulae for calculation of surface temperature in snowmelt models using frequency analysis of temperature observations

C. H. Luce,D. G. Tarboton

doi:10.5194/hess-14-535-2010

Abstract

Abstract. The snow surface temperature is an important quantity in the snow energy balance, since it modulates the exchange of energy between the surface and the atmosphere as well as the conduction of energy into the snowpack. It is therefore important to correctly model snow surface temperatures in energy balance snowmelt models. This paper focuses on the relationship between snow surface temperature and conductive energy fluxes that drive the energy balance of a snowpack. Time series of snow temperature at the surface and through the snowpack were measured to examine energy conduction in a snowpack. Based on these measurements we calculated the snowpack energy content and conductive energy flux at the snow surface. We then used these estimates of conductive energy flux to evaluate formulae for the calculation of the conductive flux at the snow surface based on surface temperature time series. We use a method based on Fourier frequency analysis to estimate snow thermal properties. Among the formulae evaluated, we found that a modified force-restore formula, based on the superimposition of the force-restore equation capturing diurnal fluctuations on a gradually changing temperature gradient, had the best agreement with observations of heat conduction. This formula is suggested for the parameterization of snow surface temperature in a full snowpack energy balance model.

Highlights

Energy balance snowmelt models include calculations for the conduction of energy into the snow forced by surface energy exchanges
This paper examines models for the calculation of conductive energy flux at the snow surface based on snow surface temperature using measured time series of snow temperature at the snow surface and through the snowpack
These measurements were made as part of an effort to validate the energy components of an energy balance snowmelt model and led to a more refined understanding of how to parameterize snow surface temperature in these models

Summary

Introduction

Energy balance snowmelt models include calculations for the conduction of energy into the snow forced by surface energy exchanges. This paper examines models for the calculation of conductive energy flux at the snow surface based on snow surface temperature using measured time series of snow temperature at the snow surface and through the snowpack. These measurements were made as part of an effort to validate the energy components of an energy balance snowmelt model and led to a more refined understanding of how to parameterize snow surface temperature in these models. Conduction of heat from the snow surface into the snowpack depends on the temperature profile within the snow that results from the history of previous energy exchanges and surface temperatures interacting with snowpack thermal properties. Because snow surface heating varies over the course of a day and over longer time periods, the temperature profile is nonlinear with depth, leading to complexity in the evolution of temperature and energy fluxes

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Conclusion