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| Titel |
The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study |
| VerfasserIn |
S. Willmes, M. Nicolaus, C. Haas |
| 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 (2014-05-16), S.891-904 |
| Datensatznummer |
250116154
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| Publikation (Nr.) |
 copernicus.org/tc-8-891-2014.pdf |
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| Zusammenfassung |
| Satellite observations of microwave brightness temperatures between 19 GHz
and 85 GHz are the main data sources for operational sea-ice monitoring and
retrieval of ice concentrations. However, microwave brightness temperatures
depend on the emissivity of snow and ice, which is subject to pronounced
seasonal variations and shows significant hemispheric contrasts. These
mainly arise from differences in the rate and strength of snow metamorphism
and melt. We here use the thermodynamic snow model SNTHERM forced by
European Re-Analysis (ERA)
interim data and the Microwave Emission Model of Layered Snowpacks (MEMLS), to calculate the sea-ice
surface emissivity and to identify the contribution of regional patterns in
atmospheric conditions to its variability in the Arctic and Antarctic. The
computed emissivities reveal a pronounced seasonal cycle with large
regional variability. The emissivity variability increases from winter to
early summer and is more pronounced in the Antarctic. In the pre-melt period
(January–May, July–November) the standard deviations in surface microwave
emissivity due to diurnal, regional and inter-annual variability of
atmospheric forcing reach up to Δε = 0.034, 0.043,
and 0.097 for 19 GHz, 37 GHz and 85 GHz channels, respectively. Between 2000
and 2009, small but significant positive emissivity trends were observed in
the Weddell Sea during November and December as well as in Fram Strait
during February, potentially related to earlier melt onset in these regions.
The obtained results contribute to a better understanding of the uncertainty
and variability of sea-ice concentration and snow-depth retrievals in
regions of high sea-ice concentrations. |
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