Preprints
https://doi.org/10.5194/tc-2020-317
https://doi.org/10.5194/tc-2020-317

  10 Nov 2020

10 Nov 2020

Review status: this preprint is currently under review for the journal TC.

Impact of water vapor diffusion and latent heat on the effective thermal conductivity of snow

Kévin Fourteau1, Florent Domine2,3, and Pascal Hagenmuller1 Kévin Fourteau et al.
  • 1Univ. Grenoble Alpes, Université de Toulouse, Météo-France, CNRS, CNRM, Centre d’Études de la Neige, Grenoble, France
  • 2Takuvik Joint International Laboratory, Université Laval (Canada) and CNRS-INSU (France), Québec, QC, G1V 0A6, Canada
  • 3Centre d’Études Nordiques (CEN) and Department of Chemistry, Université Laval, Québec, QC, G1V 0A6, Canada

Abstract. Heat transport in snowpacks is generally thought to occur through two independent processes: heat conduction and latent heat transport carried by water vapor. This paper investigates the coupling between both these processes in snow, with an emphasis on the impacts of the kinetics of the sublimation and deposition of water vapor onto ice. In the case where kinetics is fast, latent heat exchanges at ice surfaces modify their temperature, and therefore the thermal gradient within ice crystals and the heat conduction through the entire microstructure. Furthermore, in this case, the effective thermal conductivity of snow can be expressed by a purely conductive term complemented by a term directly proportional to the effective diffusion coefficient of water vapor in snow, which illustrates the inextricable coupling between heat conduction and water vapor transport. Numerical simulations on measured three-dimensional snow microstructures reveal that the effective thermal conductivity of snow can be significantly larger, up to about 50 % for low-density snow, than if water vapor transport is neglected. Comparison of our numerical simulations with literature data suggests that the fast kinetics hypothesis could be a reasonable assumption to model snow physical properties. Lastly, we demonstrate that under the fast kinetics hypothesis the effective diffusion coefficient of water vapor is related to the effective thermal conductivity by a simple linear relationship. Under such condition, the effective diffusion coefficient of water vapor is expected to lie in the narrow 100 % to about 80 % range of the value of the diffusion coefficient of water vapor in air for most seasonal snows. This may greatly facilitate the parameterization of water vapor diffusion of snow in models.

Kévin Fourteau et al.

 
Status: open (until 23 Mar 2021)
Status: open (until 23 Mar 2021)
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Kévin Fourteau et al.

Kévin Fourteau et al.

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Short summary
The thermal conductivity of snow is an important physical property, governing the thermal regime of a snowpack and of its substrate. We show that it strongly depends on the kinetics of water vapor sublimation and that previous experimental data suggest a rather fast kinetics. In such a case, neglecting water vapor leads to an underestimation of thermal conductivity, by up to 50 % for light snow. Moreover, the diffusivity of water vapor in snow is then directly related to the thermal conductivity.