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| Titel |
Detection of open water dynamics with ENVISAT ASAR in support of land surface modelling at high latitudes |
| VerfasserIn |
A. Bartsch, A. M. Trofaier, G. Hayman, D. Sabel, S. Schlaffer, D. B. Clark, E. Blyth |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 2 ; Nr. 9, no. 2 (2012-02-08), S.703-714 |
| Datensatznummer |
250006761
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| Publikation (Nr.) |
 copernicus.org/bg-9-703-2012.pdf |
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| Zusammenfassung |
Wetlands are generally accepted as being the largest but least well
quantified single source of methane (CH4). The extent of wetland or
inundation is a key factor controlling methane emissions, both in nature and
in the parameterisations used in large-scale land surface and climate models.
Satellite-derived datasets of wetland extent are available on the global
scale, but the resolution is rather coarse (>25 km). The purpose of the
present study is to assess the capability of active microwave sensors to
derive inundation dynamics for use in land surface and climate models of the
boreal and tundra environments. The focus is on synthetic aperture radar
(SAR) operating in C-band since, among microwave systems, it has comparably
high spatial resolution and data availability, and long-term continuity is
expected.
C-band data from ENVISAT ASAR (Advanced SAR) operating in wide swath mode
(150 m resolution) were investigated and an automated detection procedure
for deriving open water fraction has been developed. More than 4000 samples
(single acquisitions tiled onto 0.5° grid cells) have been analysed
for July and August in 2007 and 2008 for a study region in Western Siberia.
Simple classification algorithms were applied and found to be robust when the
water surface was smooth. Modification of input parameters results in
differences below 1 % open water fraction. The major issue to address was
the frequent occurrence of waves due to wind and precipitation, which reduces
the separability of the water class from other land cover classes.
Statistical measures of the backscatter distribution were applied in order to
retrieve suitable classification data. The Pearson correlation between each
sample dataset and a location specific representation of the bimodal
distribution was used. On average only 40 % of acquisitions allow a
separation of the open water class. Although satellite data are available
every 2–3 days over the Western Siberian study region, the irregular
acquisition intervals and periods of unsuitable weather suggest that an
update interval of 10 days is more realistic for this domain. SAR data
availability is currently limited. Future satellite missions, however, which
aim for operational services (such as Sentinel-1 with its C-band SAR
instrument), may provide the basis for inundation monitoring for land surface
and climate modelling applications. |
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