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| Titel |
A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow |
| VerfasserIn |
A. C. Hansen, W. E. Foslien |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 5 ; Nr. 9, no. 5 (2015-09-23), S.1857-1878 |
| Datensatznummer |
250116853
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| Publikation (Nr.) |
 copernicus.org/tc-9-1857-2015.pdf |
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| Zusammenfassung |
The microstructure of a dry alpine snowpack is a dynamic environment
where microstructural evolution is driven by seasonal density profiles
and weather conditions. Notably, temperature gradients on the order
of 10–20 K m−1, or larger, are known to
produce a faceted snow microstructure exhibiting little strength.
However, while strong temperature gradients are widely accepted as the
primary driver for kinetic growth, they do not fully account for the
range of experimental observations. An additional factor influencing
snow metamorphism is believed to be the rate of mass transfer at the macroscale.
We develop a mixture theory capable of predicting macroscale
deposition and/or sublimation in a snow cover under temperature
gradient conditions. Temperature gradients and mass exchange are
tracked over periods ranging from 1 to 10 days. Interesting
heat and mass transfer behavior is observed near the ground, near the
surface, as well as immediately above and below dense ice crusts.
Information about deposition (condensation) and sublimation rates may
help explain snow metamorphism phenomena that cannot be accounted for
by temperature gradients alone.
The macroscale heat and mass transfer analysis requires accurate
representations of the effective thermal conductivity and the effective mass
diffusion coefficient for snow. We develop analytical models for these
parameters based on first principles at the microscale. The
expressions derived contain no empirical adjustments, and further,
provide self consistent values for effective thermal conductivity and the
effective diffusion coefficient for the limiting cases of air and
solid ice. The predicted values for these macroscale material
parameters are also in excellent agreement with numerical results
based on microscale finite element analyses of representative volume
elements generated from X-ray tomography. |
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