Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions
Knowledge of surface hydrology is essential for many applications, including studies that aim to understand permafrost response to changing climate and the associated feedback mechanisms. Advanced remote sensing techniques make it possible to retrieve a range of land-surface variables, including rad...
Published in: | Remote Sensing |
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Ludwig-Maximilians-Universität München
2014
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Online Access: | https://epub.ub.uni-muenchen.de/24159/1/oa_24159.pdf https://epub.ub.uni-muenchen.de/24159/ http://nbn-resolving.de/urn:nbn:de:bvb:19-epub-24159-6 https://doi.org/10.3390/rs6098718 |
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ftmuenchenepub:oai:epub.ub.uni-muenchen.de:24159 2023-05-15T15:19:10+02:00 Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions Högström, Elin Trofaier, Anna Maria Gouttevin, Isabelle Bartsch, Annett 2014-09-01 application/pdf https://epub.ub.uni-muenchen.de/24159/1/oa_24159.pdf https://epub.ub.uni-muenchen.de/24159/ http://nbn-resolving.de/urn:nbn:de:bvb:19-epub-24159-6 https://doi.org/10.3390/rs6098718 eng eng Ludwig-Maximilians-Universität München Högström, Elin; Trofaier, Anna Maria; Gouttevin, Isabelle; Bartsch, Annett (September 2014): Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions. In: Remote Sensing, Vol. 6, Nr. 9: S. 8718-8738 [PDF, 5MB] https://epub.ub.uni-muenchen.de/24159/1/oa_24159.pdf http://nbn-resolving.de/urn:nbn:de:bvb:19-epub-24159-6 https://epub.ub.uni-muenchen.de/24159/ doi:10.3390/rs6098718 Remote Sensing Department für Geographie ddc:550 doc-type:article Zeitschriftenartikel PeerReviewed 2014 ftmuenchenepub https://doi.org/10.3390/rs6098718 2022-04-25T12:43:14Z Knowledge of surface hydrology is essential for many applications, including studies that aim to understand permafrost response to changing climate and the associated feedback mechanisms. Advanced remote sensing techniques make it possible to retrieve a range of land-surface variables, including radar retrieved soil moisture (SSM). It has been pointed out before that soil moisture retrieval from satellite data can be challenging at high latitudes, which correspond to remote areas where ground data are scarce and the applicability of satellite data of this type is essential. This study investigates backscatter variability other than associated with changing soil moisture in order to examine the possible impact on soil moisture retrieval. It focuses on issues specific to SSM retrieval in the Arctic, notably variations related to tundra lakes. ENVISAT Advanced Synthetic Aperture Radar (ASAR) Wide Swath (WS, 120 m) data are used to understand and quantify impacts on Metop (AAdvanced Scatterometer (ASCAT, 25 km) soil moisture retrieval during the snow free period. Sites of interest are chosen according to ASAR WS availability, high or low agreement between output from the land surface model ORCHIDEE and ASCAT derived SSM. Backscatter variations are analyzed with respect to the ASCAT footprint area. It can be shown that the low model agreement is related to water fraction in most cases. No difference could be detected between periods with floating ice (in snow off situation) and ice free periods at the chosen sites. The mean footprint backscatter is however impacted by partial short term surface roughness change. The water fraction correlates with backscatter deviations (relative to a smooth water surface reference image) within the ASCAT footprint areas (R = 0.91-0.97). Backscatter deviations of up to 5 dB can occur in areas with less than 50% water fraction and an assumed soil moisture related range (sensitivity) of 7 dB in the ASCAT data. The sensitivity is also positively correlated with water fraction in regions with low land-surface model agreement (R = 0.68). A precise quantification of the impact on soil moisture retrieval would, however, need to consider actual soil moisture changes and sensor differences. The study demonstrates that the usage of higher spatial resolution data than currently available for SSM is required in lowland permafrost environments. Article in Journal/Newspaper Arctic Ice permafrost Tundra Open Access LMU (Ludwig-Maximilians-University Munich) Arctic Asar ENVELOPE(134.033,134.033,68.667,68.667) Remote Sensing 6 9 8718 8738 |
institution |
Open Polar |
collection |
Open Access LMU (Ludwig-Maximilians-University Munich) |
op_collection_id |
ftmuenchenepub |
language |
English |
topic |
Department für Geographie ddc:550 |
spellingShingle |
Department für Geographie ddc:550 Högström, Elin Trofaier, Anna Maria Gouttevin, Isabelle Bartsch, Annett Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions |
topic_facet |
Department für Geographie ddc:550 |
description |
Knowledge of surface hydrology is essential for many applications, including studies that aim to understand permafrost response to changing climate and the associated feedback mechanisms. Advanced remote sensing techniques make it possible to retrieve a range of land-surface variables, including radar retrieved soil moisture (SSM). It has been pointed out before that soil moisture retrieval from satellite data can be challenging at high latitudes, which correspond to remote areas where ground data are scarce and the applicability of satellite data of this type is essential. This study investigates backscatter variability other than associated with changing soil moisture in order to examine the possible impact on soil moisture retrieval. It focuses on issues specific to SSM retrieval in the Arctic, notably variations related to tundra lakes. ENVISAT Advanced Synthetic Aperture Radar (ASAR) Wide Swath (WS, 120 m) data are used to understand and quantify impacts on Metop (AAdvanced Scatterometer (ASCAT, 25 km) soil moisture retrieval during the snow free period. Sites of interest are chosen according to ASAR WS availability, high or low agreement between output from the land surface model ORCHIDEE and ASCAT derived SSM. Backscatter variations are analyzed with respect to the ASCAT footprint area. It can be shown that the low model agreement is related to water fraction in most cases. No difference could be detected between periods with floating ice (in snow off situation) and ice free periods at the chosen sites. The mean footprint backscatter is however impacted by partial short term surface roughness change. The water fraction correlates with backscatter deviations (relative to a smooth water surface reference image) within the ASCAT footprint areas (R = 0.91-0.97). Backscatter deviations of up to 5 dB can occur in areas with less than 50% water fraction and an assumed soil moisture related range (sensitivity) of 7 dB in the ASCAT data. The sensitivity is also positively correlated with water fraction in regions with low land-surface model agreement (R = 0.68). A precise quantification of the impact on soil moisture retrieval would, however, need to consider actual soil moisture changes and sensor differences. The study demonstrates that the usage of higher spatial resolution data than currently available for SSM is required in lowland permafrost environments. |
format |
Article in Journal/Newspaper |
author |
Högström, Elin Trofaier, Anna Maria Gouttevin, Isabelle Bartsch, Annett |
author_facet |
Högström, Elin Trofaier, Anna Maria Gouttevin, Isabelle Bartsch, Annett |
author_sort |
Högström, Elin |
title |
Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions |
title_short |
Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions |
title_full |
Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions |
title_fullStr |
Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions |
title_full_unstemmed |
Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions |
title_sort |
assessing seasonal backscatter variations with respect to uncertainties in soil moisture retrieval in siberian tundra regions |
publisher |
Ludwig-Maximilians-Universität München |
publishDate |
2014 |
url |
https://epub.ub.uni-muenchen.de/24159/1/oa_24159.pdf https://epub.ub.uni-muenchen.de/24159/ http://nbn-resolving.de/urn:nbn:de:bvb:19-epub-24159-6 https://doi.org/10.3390/rs6098718 |
long_lat |
ENVELOPE(134.033,134.033,68.667,68.667) |
geographic |
Arctic Asar |
geographic_facet |
Arctic Asar |
genre |
Arctic Ice permafrost Tundra |
genre_facet |
Arctic Ice permafrost Tundra |
op_source |
Remote Sensing |
op_relation |
Högström, Elin; Trofaier, Anna Maria; Gouttevin, Isabelle; Bartsch, Annett (September 2014): Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions. In: Remote Sensing, Vol. 6, Nr. 9: S. 8718-8738 [PDF, 5MB] https://epub.ub.uni-muenchen.de/24159/1/oa_24159.pdf http://nbn-resolving.de/urn:nbn:de:bvb:19-epub-24159-6 https://epub.ub.uni-muenchen.de/24159/ doi:10.3390/rs6098718 |
op_doi |
https://doi.org/10.3390/rs6098718 |
container_title |
Remote Sensing |
container_volume |
6 |
container_issue |
9 |
container_start_page |
8718 |
op_container_end_page |
8738 |
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1766349350859964416 |