A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland
We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration–validation sites on Devon Ice Cap and western Greenland. Comparisons are included for both the heights derived from the first return (the point-of-closest-approach or POCA) and he...
Published in: | The Cryosphere |
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Format: | Article in Journal/Newspaper |
Language: | English |
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Copernicus Publications
2017
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00010265 2023-05-15T16:26:36+02:00 A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland Gray, Laurence Burgess, David Copland, Luke Dunse, Thorben Langley, Kirsty Moholdt, Geir 2017-05 electronic https://doi.org/10.5194/tc-11-1041-2017 https://noa.gwlb.de/receive/cop_mods_00010265 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00010222/tc-11-1041-2017.pdf https://tc.copernicus.org/articles/11/1041/2017/tc-11-1041-2017.pdf eng eng Copernicus Publications The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-11-1041-2017 https://noa.gwlb.de/receive/cop_mods_00010265 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00010222/tc-11-1041-2017.pdf https://tc.copernicus.org/articles/11/1041/2017/tc-11-1041-2017.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2017 ftnonlinearchiv https://doi.org/10.5194/tc-11-1041-2017 2022-02-08T22:57:09Z We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration–validation sites on Devon Ice Cap and western Greenland. Comparisons are included for both the heights derived from the first return (the point-of-closest-approach or POCA) and heights derived from delayed waveform returns (swath processing). While swath-processed heights are normally less precise than edited POCA heights, e.g. standard deviations of ∼ 3 and ∼ 1.5 m respectively for the western Greenland site, the increased coverage possible with swath data complements the POCA data and provides useful information for both system calibration and improving digital elevation models (DEMs). We show that the pre-launch interferometric baseline coupled with an additional roll correction ( ∼ 0.0075° ± 0.0025°), or equivalent phase correction ( ∼ 0.0435 ± 0.0145 radians), provides an improved calibration of the interferometric SARIn mode. We extend the potential use of SARIn data by showing the influence of surface conditions, especially melt, on the return waveforms and that it is possible to detect and measure the height of summer supraglacial lakes in western Greenland. A supraglacial lake can provide a strong radar target in the waveform, stronger than the initial POCA return, if viewed at near-normal incidence. This provides an ideal situation for swath processing and we demonstrate a height precision of ∼ 0.5 m for two lake sites, one in the accumulation zone and one in the ablation zone, which were measured every year from 2010 or 2011 to 2016. Each year the lake in the ablation zone was viewed in June by ascending passes and then 5.5 days later by descending passes, which allows an approximate estimate of the filling rate. The results suggest that CryoSat waveform data and measurements of supraglacial lake height change could complement the use of optical satellite imagery and be helpful as proxy indicators for surface melt around Greenland. Article in Journal/Newspaper Greenland Ice cap The Cryosphere Niedersächsisches Online-Archiv NOA Greenland Devon Ice Cap ENVELOPE(-82.499,-82.499,75.335,75.335) The Cryosphere 11 3 1041 1058 |
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English |
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article Verlagsveröffentlichung |
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article Verlagsveröffentlichung Gray, Laurence Burgess, David Copland, Luke Dunse, Thorben Langley, Kirsty Moholdt, Geir A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
topic_facet |
article Verlagsveröffentlichung |
description |
We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration–validation sites on Devon Ice Cap and western Greenland. Comparisons are included for both the heights derived from the first return (the point-of-closest-approach or POCA) and heights derived from delayed waveform returns (swath processing). While swath-processed heights are normally less precise than edited POCA heights, e.g. standard deviations of ∼ 3 and ∼ 1.5 m respectively for the western Greenland site, the increased coverage possible with swath data complements the POCA data and provides useful information for both system calibration and improving digital elevation models (DEMs). We show that the pre-launch interferometric baseline coupled with an additional roll correction ( ∼ 0.0075° ± 0.0025°), or equivalent phase correction ( ∼ 0.0435 ± 0.0145 radians), provides an improved calibration of the interferometric SARIn mode. We extend the potential use of SARIn data by showing the influence of surface conditions, especially melt, on the return waveforms and that it is possible to detect and measure the height of summer supraglacial lakes in western Greenland. A supraglacial lake can provide a strong radar target in the waveform, stronger than the initial POCA return, if viewed at near-normal incidence. This provides an ideal situation for swath processing and we demonstrate a height precision of ∼ 0.5 m for two lake sites, one in the accumulation zone and one in the ablation zone, which were measured every year from 2010 or 2011 to 2016. Each year the lake in the ablation zone was viewed in June by ascending passes and then 5.5 days later by descending passes, which allows an approximate estimate of the filling rate. The results suggest that CryoSat waveform data and measurements of supraglacial lake height change could complement the use of optical satellite imagery and be helpful as proxy indicators for surface melt around Greenland. |
format |
Article in Journal/Newspaper |
author |
Gray, Laurence Burgess, David Copland, Luke Dunse, Thorben Langley, Kirsty Moholdt, Geir |
author_facet |
Gray, Laurence Burgess, David Copland, Luke Dunse, Thorben Langley, Kirsty Moholdt, Geir |
author_sort |
Gray, Laurence |
title |
A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
title_short |
A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
title_full |
A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
title_fullStr |
A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
title_full_unstemmed |
A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
title_sort |
revised calibration of the interferometric mode of the cryosat-2 radar altimeter improves ice height and height change measurements in western greenland |
publisher |
Copernicus Publications |
publishDate |
2017 |
url |
https://doi.org/10.5194/tc-11-1041-2017 https://noa.gwlb.de/receive/cop_mods_00010265 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00010222/tc-11-1041-2017.pdf https://tc.copernicus.org/articles/11/1041/2017/tc-11-1041-2017.pdf |
long_lat |
ENVELOPE(-82.499,-82.499,75.335,75.335) |
geographic |
Greenland Devon Ice Cap |
geographic_facet |
Greenland Devon Ice Cap |
genre |
Greenland Ice cap The Cryosphere |
genre_facet |
Greenland Ice cap The Cryosphere |
op_relation |
The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-11-1041-2017 https://noa.gwlb.de/receive/cop_mods_00010265 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00010222/tc-11-1041-2017.pdf https://tc.copernicus.org/articles/11/1041/2017/tc-11-1041-2017.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/tc-11-1041-2017 |
container_title |
The Cryosphere |
container_volume |
11 |
container_issue |
3 |
container_start_page |
1041 |
op_container_end_page |
1058 |
_version_ |
1766015534275493888 |