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| Titel |
Hoar crystal development and disappearance at Dome C, Antarctica: observation by near-infrared photography and passive microwave satellite |
| VerfasserIn |
N. Champollion, G. Picard, L. Arnaud, E. Lefebvre, 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 ; 7, no. 4 ; Nr. 7, no. 4 (2013-08-08), S.1247-1262 |
| Datensatznummer |
250085145
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| Publikation (Nr.) |
 copernicus.org/tc-7-1247-2013.pdf |
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| Zusammenfassung |
| Hoar crystals episodically cover the snow surface in
Antarctica and affect the roughness and reflective properties of the air–snow
interface. However, little is known about their evolution and the processes
responsible for their development and disappearance despite a probable
influence on the surface mass balance and energy budget. To investigate hoar
evolution, we use continuous observations of the surface by in situ
near-infrared photography and by passive microwave remote sensing at Dome C
in Antarctica. From the photography data, we retrieved a daily indicator of
the presence/absence of hoar crystals using a texture analysis algorithm. The
analysis of this 2 yr long time series shows that Dome C surface is covered
almost half of the time by hoar. The development of hoar crystals takes a few
days and seems to occur whatever the meteorological conditions. In contrast,
the disappearance of hoar is rapid (a few hours) and coincident with either
strong winds or with moderate winds associated with a change in wind
direction from southwest (the prevailing direction) to southeast. From the
microwave satellite data, we computed the polarisation ratio (i.e. horizontal
over vertical polarised brightness temperatures), an indicator known to be
sensitive to hoar in Greenland. Photography data and microwave polarisation
ratio are correlated, i.e. high values of polarisation ratio which
theoretically correspond to low snow density values near the surface are
associated with the presence of hoar crystals in the photography data.
Satellite data over nearly ten years (2002–2011) confirm that a strong
decrease of the polarisation ratio (i.e. signature of hoar disappearance) is
associated with an increase of wind speed or a change in wind direction from
the prevailing direction. The photography data provides, in addition,
evidence of interactions between hoar and snowfall. Further adding the
combined influence of wind speed and wind direction results in a complex
picture of the snow–atmosphere interactions in Antarctica which deserves
further quantification and modelling. |
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