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| Titel |
A snow cover climatology for the Pyrenees from MODIS snow products |
| VerfasserIn |
S. Gascoin, O. Hagolle, M. Huc, L. Jarlan, J.-F. Dejoux, C. Szczypta, R. Marti, R. Sánchez |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 5 ; Nr. 19, no. 5 (2015-05-19), S.2337-2351 |
| Datensatznummer |
250120714
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| Publikation (Nr.) |
 copernicus.org/hess-19-2337-2015.pdf |
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| Zusammenfassung |
| The seasonal snow in the Pyrenees is critical for hydropower
production, crop irrigation and tourism in France, Spain and
Andorra. Complementary to in situ observations, satellite remote
sensing is useful to monitor the effect of climate on the snow
dynamics. The MODIS daily snow products (Terra/MOD10A1 and
Aqua/MYD10A1) are widely used to generate snow cover climatologies,
yet it is preferable to assess their accuracies prior to their
use. Here, we use both in situ snow observations and remote sensing
data to evaluate the MODIS snow products in the Pyrenees. First, we
compare the MODIS products to in situ snow depth (SD) and snow water
equivalent (SWE) measurements. We estimate the values of the SWE and
SD best detection thresholds to 40 mm water equivalent (w.e.)
and 150 mm, respectively, for both MOD10A1 and MYD10A1. κ
coefficients are within 0.74 and 0.92 depending on the product and
the variable for these thresholds. However, we also find a seasonal trend in
the optimal SWE and SD thresholds, reflecting the hysteresis in the
relationship between the depth of the snowpack (or SWE) and its extent within
a MODIS pixel.
Then, a set of Landsat images is used to validate
MOD10A1 and MYD10A1 for 157 dates between 2002 and 2010. The
resulting accuracies are 97% (κ = 0.85) for MOD10A1 and
96% (κ = 0.81) for MYD10A1, which indicates a good
agreement between both data sets. The effect of vegetation on the
results is analyzed by filtering the forested areas using a land
cover map. As expected, the accuracies decrease over the forests
but the agreement remains acceptable (MOD10A1: 96%,
κ = 0.77; MYD10A1: 95%, κ = 0.67). We conclude that
MODIS snow products have a sufficient accuracy for hydroclimate
studies at the scale of the Pyrenees range. Using a gap-filling
algorithm we generate a consistent snow cover climatology, which
allows us to compute the mean monthly snow cover duration per
elevation band and aspect classes. There is snow on the ground at least 50% of the time above 1600 m between December and April.
We finally analyze the snow patterns for the
atypical winter 2011–2012. Snow cover duration anomalies reveal
a deficient snowpack on the Spanish side of the Pyrenees, which
seems to have caused a drop in the national hydropower production. |
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