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| Titel |
Influence of meter-scale wind-formed features on the variability of the microwave brightness temperature around Dome C in Antarctica |
| VerfasserIn |
G. Picard, A. Royer, L. Arnaud, M. Fily |
| 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. 3 ; Nr. 8, no. 3 (2014-06-24), S.1105-1119 |
| Datensatznummer |
250116169
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| Publikation (Nr.) |
 copernicus.org/tc-8-1105-2014.pdf |
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| Zusammenfassung |
| Space-borne passive microwave radiometers are widely used to retrieve
information in snowy regions by exploiting the high sensitivity of microwave
emission to snow properties. For the Antarctic Plateau, many studies
presenting retrieval algorithms or numerical simulations have assumed,
explicitly or not, that the subpixel-scale heterogeneity is negligible and
that the retrieved properties were representative of whole pixels. In this
paper, we investigate the spatial variations of brightness temperature over a
range of a few kilometers in the Dome C area. Using ground-based radiometers
towed by a vehicle, we collected brightness temperature at 11, 19 and 37 GHz
at horizontal and vertical polarizations along transects with meter
resolution. The most remarkable observation was a series of regular
undulations of the signal with a significant amplitude reaching 10 K at
37 GHz and a quasi-period of 30–50 m. In contrast, the variability at
longer length scales seemed to be weak in the investigated area, and the mean
brightness temperature was close to SSM/I and WindSat satellite observations
for all the frequencies and polarizations. To establish a link between the
snow characteristics and the microwave emission undulations, we collected
detailed snow grain size and density profiles at two points where opposite
extrema of brightness temperature were observed. Numerical simulations with
the DMRT-ML microwave emission model revealed that the difference in density
in the upper first meter explained most of the brightness temperature
variations. In addition, we found that these variations of density near the
surface were linked to snow hardness. Patches of hard snow – probably formed
by wind compaction – were clearly visible and covered as much as 39% of
the investigated area. Their brightness temperature was higher than in normal
areas. This result implies that the microwave emission measured by satellites
over Dome C is more complex than expected and very likely depends on the
year-to-year areal proportion of the two different types of snow. |
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