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160 Energy Balance and Thermophysical Processes in Snowpacks

Part 14. Snow and Glacier Hydrology

  1. Michael Lehning

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa166

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Lehning, M. 2006. Energy Balance and Thermophysical Processes in Snowpacks. Encyclopedia of Hydrological Sciences. 14:160.

Author Information

  1. WSL, Swiss Federal Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland

Publication History

  1. Published Online: 15 APR 2006

Abstract

This contribution discusses heat and mass fluxes relating to snow. The first process treated is heat flux through snow. Snow can be described as a bulk material or as consisting of different phases. When a separate water vapor phase is considered, vertical mass flux due to vapor pressure differences can be treated. A significant amount of heat is transported along with the vapor fluxes because of the phase changes occurring when water molecules enter the vapor phase at one point and deposit back onto the ice matrix somewhere else. The vapor fluxes in snow also cause snow metamorphism changing the crystals' form and size. Equilibrium metamorphism dominates when weak, large-scale temperature gradients exist, and water molecules are mainly rearranged locally by surface tension differences. Metamorphism is called kinetic when vertical vapor fluxes due to a large-scale temperature gradient lead to a snow crystal re-formation.

Mass- and energy fluxes in the snow cover are driven by surface exchange. The surface turbulent fluxes of sensible heat and moisture are derived from atmospheric surface layer similarity theory. The long-wave radiation balance leads to a strong surface cooling especially during cold nights. Short-wave radiation penetrates the snow cover and deposits energy at greater depths. Finally, the surface mass transport process of snow redistribution is treated with its subprocesses, saltation and suspension.

Keywords:

  • heat transport;
  • vapor transport;
  • metamorphism;
  • porous medium;
  • phase changes;
  • ice matrix;
  • turbulent fluxes;
  • radiation balance;
  • radiation penetration;
  • snow transport;
  • saltation;
  • suspension