An attempt to improve snow depth retrieval using satellite microwave radiometry for rough antarctic sea ice

Stefan Kern; Burcu Ozsoy

doi:10.3390/rs11192323

An attempt to improve snow depth retrieval using satellite microwave radiometry for rough antarctic sea ice

Stefan Kern^*, Burcu Ozsoy

^*Corresponding author for this work

Department of Maritime Transportation and Management Engineering

University of Hamburg

Research output: Contribution to journal › Article › peer-review

6 Citations (Scopus)

Abstract

Snow depth on sea ice is a major constituent of the marine cryosphere. It is a key parameter for the derivation of sea-ice thickness from satellite altimetry. One way to retrieve the basin-scale snow depth on sea ice is by satellite microwave radiometry. There is evidence from measurements and inter-comparison studies that current retrievals likely under-estimate the snow depth over deformed, rough sea ice. We follow up on an earlier study, where satellite passive microwave data were combined with information on the sea-ice topography from the satellite laser altimeter on board the Ice, Cloud and land Elevation Satellite (ICESat) in a hybrid approach. Such topography information is spatiotemporally limited because of ICESat's operation mode. In this paper, we aim to derive a proxy for this topography information from satellite microwave radiometry. For this purpose, we co-locate parameters describing the sea-ice deformation taken from visual ship-based observations and the surface elevation standard deviation derived from ICESat laser altimetry with the microwave brightness temperatures (TB) measured via the Advanced Microwave Scanning Radiometer aboard Earth Observation Satellite (AMSR-E) and aboard Global Change Observation Mission-Water 1 (GCOM-W1) (AMSR2). We find that the TB polarization ratio at 6.9 GHz and the TB gradient ratio between 10.7 GHz (horizontal polarization) and 6.9 GHz (vertical polarization), might be suited as such a proxy. Using this proxy, we modify the above-mentioned hybrid approach and compute the snow depths on sea ice from the AMSR-E and AMSR2 data. We compare our snow depths with those of the commonly used approach, the hybrid approach, with the ship-based observations for the years 2002 through 2015 and with the measurements made by drifting buoys for the period of 2014 through 2018. We find a convincing overall agreement with the hybrid approach and some improvement over the common approach. However, our approach is sensitive to the presence of thin ice-here, the retrieved snow depths are too large; and our approach performs sub-optimally over old ice-here, the retrieved snow depths are too small. More investigations and, in particular, more evaluations are required to optimize our approach so that the snow depths retrieved for the combined AMSR-E/AMSR2 period could serve as a data set for sea-ice thickness retrieval based on satellite altimetry.

Original language	English
Article number	2323
Journal	Remote Sensing
Volume	11
Issue number	19
DOIs	https://doi.org/10.3390/rs11192323
Publication status	Published - 1 Oct 2019

Bibliographical note

Publisher Copyright:
© 2019 by the authors.

Funding

This study was financially supported by the National Natural Science Foundation of China (grant #41571411) and by the National Key R&D Program of China project 'Research of Key Technologies for Monitoring Forest Plantation Resources' (2017YFD0600900). The authors would like to thank Lei Zhao, Longwei Li, Xiaozhi Yu, and Yahui Wang for their help in data collection. In particular, the authors would like to thank Yudong Jin from the Wangyedian Experimental Forest Farm, Chifeng, Inner Mongolia Autonomous Region, for his great support during field work. This research was funded by the European Commission under grand number H2020-EO-2014-SPICES, by the ESA (through the Climate Change Initiative Sea_Ice:cci project), and by the German Research Foundation (DFG) Excellence Initiative CLISAP under Grant EXC 177/2. We acknowledge scientific discussion and support by the project teams of the ESA-CCI sea-ice ECV project and of the EU-2020 project SPICES. We acknowledge the University of Hamburg and the Technical University of Istanbul for working environment and administrative services provided. We are very grateful for the helpful comments of two reviewers greatly enhancing the quality of our paper. Funding: This research was funded by the European Commission under grand number H2020-EO-2014–SPICES, by the ESA (through the Climate Change Initiative Sea_Ice_cci project), and by the German Research Foundation (DFG) Excellence Initiative CLISAP under Grant EXC 177/2.

Funders	Funder number
Ecological Society of America
European Commission	H2020-EO-2014, H2020-EO-2014-SPICES
European Space Agency
Deutsche Forschungsgemeinschaft	EXC 177/2
National Natural Science Foundation of China	41571411
Universität Hamburg
National Key Research and Development Program of China	2017YFD0600900

Keywords

AMSR-E
AMSR2
Buoy observations
Marine cryosphere
Microwave radiometry
Satellite remote sensing
Sea ice
Ship-based observations
Snow depth

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title = "An attempt to improve snow depth retrieval using satellite microwave radiometry for rough antarctic sea ice",

abstract = "Snow depth on sea ice is a major constituent of the marine cryosphere. It is a key parameter for the derivation of sea-ice thickness from satellite altimetry. One way to retrieve the basin-scale snow depth on sea ice is by satellite microwave radiometry. There is evidence from measurements and inter-comparison studies that current retrievals likely under-estimate the snow depth over deformed, rough sea ice. We follow up on an earlier study, where satellite passive microwave data were combined with information on the sea-ice topography from the satellite laser altimeter on board the Ice, Cloud and land Elevation Satellite (ICESat) in a hybrid approach. Such topography information is spatiotemporally limited because of ICESat's operation mode. In this paper, we aim to derive a proxy for this topography information from satellite microwave radiometry. For this purpose, we co-locate parameters describing the sea-ice deformation taken from visual ship-based observations and the surface elevation standard deviation derived from ICESat laser altimetry with the microwave brightness temperatures (TB) measured via the Advanced Microwave Scanning Radiometer aboard Earth Observation Satellite (AMSR-E) and aboard Global Change Observation Mission-Water 1 (GCOM-W1) (AMSR2). We find that the TB polarization ratio at 6.9 GHz and the TB gradient ratio between 10.7 GHz (horizontal polarization) and 6.9 GHz (vertical polarization), might be suited as such a proxy. Using this proxy, we modify the above-mentioned hybrid approach and compute the snow depths on sea ice from the AMSR-E and AMSR2 data. We compare our snow depths with those of the commonly used approach, the hybrid approach, with the ship-based observations for the years 2002 through 2015 and with the measurements made by drifting buoys for the period of 2014 through 2018. We find a convincing overall agreement with the hybrid approach and some improvement over the common approach. However, our approach is sensitive to the presence of thin ice-here, the retrieved snow depths are too large; and our approach performs sub-optimally over old ice-here, the retrieved snow depths are too small. More investigations and, in particular, more evaluations are required to optimize our approach so that the snow depths retrieved for the combined AMSR-E/AMSR2 period could serve as a data set for sea-ice thickness retrieval based on satellite altimetry.",

keywords = "AMSR-E, AMSR2, Buoy observations, Marine cryosphere, Microwave radiometry, Satellite remote sensing, Sea ice, Ship-based observations, Snow depth",

author = "Stefan Kern and Burcu Ozsoy",

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AU - Kern, Stefan

AU - Ozsoy, Burcu

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N2 - Snow depth on sea ice is a major constituent of the marine cryosphere. It is a key parameter for the derivation of sea-ice thickness from satellite altimetry. One way to retrieve the basin-scale snow depth on sea ice is by satellite microwave radiometry. There is evidence from measurements and inter-comparison studies that current retrievals likely under-estimate the snow depth over deformed, rough sea ice. We follow up on an earlier study, where satellite passive microwave data were combined with information on the sea-ice topography from the satellite laser altimeter on board the Ice, Cloud and land Elevation Satellite (ICESat) in a hybrid approach. Such topography information is spatiotemporally limited because of ICESat's operation mode. In this paper, we aim to derive a proxy for this topography information from satellite microwave radiometry. For this purpose, we co-locate parameters describing the sea-ice deformation taken from visual ship-based observations and the surface elevation standard deviation derived from ICESat laser altimetry with the microwave brightness temperatures (TB) measured via the Advanced Microwave Scanning Radiometer aboard Earth Observation Satellite (AMSR-E) and aboard Global Change Observation Mission-Water 1 (GCOM-W1) (AMSR2). We find that the TB polarization ratio at 6.9 GHz and the TB gradient ratio between 10.7 GHz (horizontal polarization) and 6.9 GHz (vertical polarization), might be suited as such a proxy. Using this proxy, we modify the above-mentioned hybrid approach and compute the snow depths on sea ice from the AMSR-E and AMSR2 data. We compare our snow depths with those of the commonly used approach, the hybrid approach, with the ship-based observations for the years 2002 through 2015 and with the measurements made by drifting buoys for the period of 2014 through 2018. We find a convincing overall agreement with the hybrid approach and some improvement over the common approach. However, our approach is sensitive to the presence of thin ice-here, the retrieved snow depths are too large; and our approach performs sub-optimally over old ice-here, the retrieved snow depths are too small. More investigations and, in particular, more evaluations are required to optimize our approach so that the snow depths retrieved for the combined AMSR-E/AMSR2 period could serve as a data set for sea-ice thickness retrieval based on satellite altimetry.

AB - Snow depth on sea ice is a major constituent of the marine cryosphere. It is a key parameter for the derivation of sea-ice thickness from satellite altimetry. One way to retrieve the basin-scale snow depth on sea ice is by satellite microwave radiometry. There is evidence from measurements and inter-comparison studies that current retrievals likely under-estimate the snow depth over deformed, rough sea ice. We follow up on an earlier study, where satellite passive microwave data were combined with information on the sea-ice topography from the satellite laser altimeter on board the Ice, Cloud and land Elevation Satellite (ICESat) in a hybrid approach. Such topography information is spatiotemporally limited because of ICESat's operation mode. In this paper, we aim to derive a proxy for this topography information from satellite microwave radiometry. For this purpose, we co-locate parameters describing the sea-ice deformation taken from visual ship-based observations and the surface elevation standard deviation derived from ICESat laser altimetry with the microwave brightness temperatures (TB) measured via the Advanced Microwave Scanning Radiometer aboard Earth Observation Satellite (AMSR-E) and aboard Global Change Observation Mission-Water 1 (GCOM-W1) (AMSR2). We find that the TB polarization ratio at 6.9 GHz and the TB gradient ratio between 10.7 GHz (horizontal polarization) and 6.9 GHz (vertical polarization), might be suited as such a proxy. Using this proxy, we modify the above-mentioned hybrid approach and compute the snow depths on sea ice from the AMSR-E and AMSR2 data. We compare our snow depths with those of the commonly used approach, the hybrid approach, with the ship-based observations for the years 2002 through 2015 and with the measurements made by drifting buoys for the period of 2014 through 2018. We find a convincing overall agreement with the hybrid approach and some improvement over the common approach. However, our approach is sensitive to the presence of thin ice-here, the retrieved snow depths are too large; and our approach performs sub-optimally over old ice-here, the retrieved snow depths are too small. More investigations and, in particular, more evaluations are required to optimize our approach so that the snow depths retrieved for the combined AMSR-E/AMSR2 period could serve as a data set for sea-ice thickness retrieval based on satellite altimetry.

KW - AMSR-E

KW - AMSR2

KW - Buoy observations

KW - Marine cryosphere

KW - Microwave radiometry

KW - Satellite remote sensing

KW - Sea ice

KW - Ship-based observations

KW - Snow depth

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An attempt to improve snow depth retrieval using satellite microwave radiometry for rough antarctic sea ice

Abstract

Bibliographical note

Funding

Keywords

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