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| Titel |
Intercomparison of retrieval algorithms for the specific surface area of snow from near-infrared satellite data in mountainous terrain, and comparison with the output of a semi-distributed snowpack model |
| VerfasserIn |
A. Mary, M. Dumont, J.-P. Dedieu, Y. Durand, P. Sirguey, H. Milhem, O. Mestre, H. S. Negi, A. A. Kokhanovsky, M. Lafaysse, S. Morin |
| 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 ; 7, no. 2 ; Nr. 7, no. 2 (2013-04-29), S.741-761 |
| Datensatznummer |
250017963
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| Publikation (Nr.) |
 copernicus.org/tc-7-741-2013.pdf |
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| Zusammenfassung |
| This study compares different methods to retrieve the specific surface area
(SSA) of snow from satellite radiance measurements in mountainous terrain.
It aims at addressing the effect on the retrieval of topographic corrections
of reflectance, namely slope and aspect of terrain, multiple reflections on
neighbouring slopes and accounting (or not) for the anisotropy of snow
reflectance. Using MODerate resolution Imaging Spectrometer (MODIS) data
for six different clear sky scenes spanning a wide range of snow conditions
during the winter season 2008–2009 over a domain of 46 × 50 km in
the French Alps, we compared SSA retrievals with and without topographic
correction, with a spherical or non-spherical snow reflectance model and, in
spherical case, with or without anisotropy corrections. The retrieved SSA
values were compared to field measurements and to the results of the
detailed snowpack model Crocus, fed by driving data from the SAFRAN
meteorological analysis. It was found that the difference in terms of
surface SSA between retrieved values and SAFRAN-Crocus output was minimal
when the topographic correction was taken into account, when using a
retrieval method assuming disconnected spherical snow grains. In this case,
the root mean square deviation was 9.4 m2 kg−1 and the mean
difference was 0.1 m2 kg−1, based on 3170 pairs of observation
and simulated values. The added-value of the anisotropy correction was
not significant in our case, which may be explained by the presence of
mixed pixels and surface roughness. MODIS retrieved data show SSA variations
with elevation and aspect which are physically consistent and in good
agreement with SAFRAN-Crocus outputs. The variability of the MODIS
retrieved SSA within the topographic classes of the model was found to be
relatively small (3.9 m2 kg−1). This indicates that
semi-distributed snowpack simulations in mountainous terrain with a
sufficiently large number of classes provides a representation of the
snowpack variability consistent with the scale of MODIS 500 m pixels. |
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