The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study.

Willmes, Sascha, Nicolaus, Marcel and Haas, Christian (2014) The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study. The Cryosphere, 8 (3). pp. 891-904. DOI 10.5194/tc-8-891-2014.

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Abstract

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.

Document Type: Article
Additional Information: WOS:000338655600007
Keywords: Layered snowpacks; Seasonal cycle; Retrievals; Signatures; Surface; Depth; Onset; Melt; Simulations; Reduction; SNTHERM; MEMLS; Arctic; Antarctic
Research affiliation: AWI
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/tc-8-891-2014
ISSN: 1994-0416
Projects: Transdrift, Laptev Sea System
Date Deposited: 15 Jan 2015 08:34
Last Modified: 15 Jan 2015 08:34
URI: http://oceanrep.geomar.de/id/eprint/26951

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