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| Titel |
An improved CryoSat-2 sea ice freeboard retrieval algorithm through the use of waveform fitting |
| VerfasserIn |
N. T. Kurtz, N. Galin, M. Studinger |
| 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. 4 ; Nr. 8, no. 4 (2014-07-15), S.1217-1237 |
| Datensatznummer |
250116244
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| Publikation (Nr.) |
 copernicus.org/tc-8-1217-2014.pdf |
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| Zusammenfassung |
| We develop a physical model capable of simulating the mean echo power of
CryoSat-2 SAR- and SARIn-mode waveforms over sea-ice-covered regions. The
model simulations are used to show the importance of variations in the radar
backscatter coefficient with incidence angle and surface roughness for the
retrieval of surface elevation of both sea ice floes and leads. The physical
model is used to fit CryoSat-2 waveforms to enable retrieval of surface
elevation through the use of lookup tables and a bounded trust region Newton
least-squares fitting approach. The use of a model to fit returns from sea
ice regions offers advantages over currently used threshold retracking
methods, which are here shown to be sensitive to the combined effect of
bandwidth-limited range resolution and surface roughness variations. Laxon et
al. (2013) have compared ice thickness results from CryoSat-2 and IceBridge,
and found good agreement; however consistent assumptions about the snow depth
and density of sea ice were not used in the comparisons. To address this
issue, we directly compare ice freeboard and thickness retrievals from the
waveform-fitting and threshold tracker methods of CryoSat-2 to Operation
IceBridge data using a consistent set of parameterizations. The purpose of
the comparison is to highlight the physical basis between differences in the
retracking methods. For three IceBridge campaign periods from March
2011 to March 2013, mean differences (CryoSat-2 – IceBridge) of 0.144 and
1.351 m are found between the freeboard and thickness
retrievals, respectively, using a 50% sea ice floe threshold retracker, while mean
differences of 0.019 and 0.182 m are found when using the waveform-fitting
method. This suggests the waveform-fitting technique is capable of
better reconciling the sea ice thickness data record from laser and radar
altimetry data sets through the usage of consistent physical assumptions. |
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