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| Titel |
Measuring the specific surface area of wet snow using 1310 nm reflectance |
| VerfasserIn |
J.-C. Gallet, F. Domine, M. Dumont |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2014-07-03), S.1139-1148 |
| Datensatznummer |
250116238
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| Publikation (Nr.) |
 copernicus.org/tc-8-1139-2014.pdf |
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| Zusammenfassung |
| The specific surface area (SSA) of snow can be used as an objective
measurement of grain size and is therefore a central variable to describe
snow physical properties such as albedo. Snow SSA can now be easily measured
in the field using optical methods based on infrared reflectance. However,
existing optical methods have only been validated for dry snow. Here we test
the possibility to use the DUFISSS instrument, based on the measurement of
the 1310 nm reflectance of snow with an integrating sphere, to measure the
SSA of wet snow. We perform cold room experiments where we measure the SSA
of a wet snow sample, freeze it and measure it again, to quantify the
difference in reflectance between frozen and wet snow. We study snow samples
in the SSA range 12–37 m2 kg−1 and in the mass liquid water
content (LWC) range 5–32%. We conclude that the SSA of wet snow can be
obtained from the measurement of its 1310 nm reflectance using three simple
steps. In most cases, the SSA thus obtained is less than 10 {%} different
from the value that would have been obtained if the sample had been
considered dry, so that the three simple steps constitute a minor
correction. We also run two optical models to interpret the results, but no
model reproduces correctly the water–ice distribution in wet snow, so that
their predictions of wet snow reflectance are imperfect. The correction on
the determination of wet snow SSA using the DUFISSS instrument gives an
overall uncertainty better than 11%, even if the LWC is unknown. If SSA
is expressed as a surface to volume ratio (e.g., in mm−1), the
uncertainty is then 13% because of additional uncertainties in the
determination of the volume of ice and water when the LWC is unknown. |
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