Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice
<p>Sea ice thickness is an essential climate variable. Current L-Band sea ice thickness retrieval methods do not account for sea ice surface roughness that is hypothesised to be not relevant to the process. This study attempts to validate this hypothesis that has not been tested yet. To test t...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2020-02-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/14/461/2020/tc-14-461-2020.pdf |
| _version_ | 1828767757684965376 |
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| author | M. Miernecki M. Miernecki L. Kaleschke L. Kaleschke N. Maaß S. Hendricks S. S. Søbjærg |
| author_facet | M. Miernecki M. Miernecki L. Kaleschke L. Kaleschke N. Maaß S. Hendricks S. S. Søbjærg |
| author_sort | M. Miernecki |
| collection | DOAJ |
| description | <p>Sea ice thickness is an essential climate variable. Current L-Band sea ice thickness retrieval methods do not account for sea ice surface roughness that is hypothesised to be not relevant to the process. This study attempts to validate this hypothesis that has not been tested yet. To test this hypothesis, we created a physical model of sea ice roughness based on geometrical optics and merged it into the L-band emissivity model of sea ice that is similar to the one used in the operational sea ice thickness retrieval algorithm. The facet description of sea ice surface used in geometrical optics is derived from 2-D surface elevation measurements. Subsequently the new model was tested with <span class="inline-formula"><i>T</i><sub>B</sub></span> measurements performed during the SMOSice 2014 field campaign. Our simulation results corroborate the hypothesis that sea ice surface roughness has a marginal impact on near-nadir <span class="inline-formula"><i>T</i><sub>B</sub></span> (used in the current operational retrieval). We demonstrate that the probability distribution function of surface slopes can be approximated with a parametric function whose single parameter can be used to characterise the degree of roughness. Facet azimuth orientation is isotropic at scales greater than 4.3 km. The simulation results indicate that surface roughness is a minor factor in modelling the sea ice brightness temperature. The change in <span class="inline-formula"><i>T</i><sub>B</sub></span> is most pronounced at incidence angles greater than 40<span class="inline-formula"><sup>∘</sup></span> and can reach up to 8 K for vertical polarisation at 60<span class="inline-formula"><sup>∘</sup></span>. Therefore current and future L-band missions (SMOS, SMAP, CIMR, SMOS-HR) measuring at such angles can be affected. Comparison of the brightness temperature simulations with the SMOSice 2014 radiometer data does not yield definite results.</p> |
| first_indexed | 2024-12-11T07:33:50Z |
| format | Article |
| id | doaj.art-c2c97ddbe1be4e83a90deb0e4bf7f11c |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-12-11T07:33:50Z |
| publishDate | 2020-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-c2c97ddbe1be4e83a90deb0e4bf7f11c2022-12-22T01:15:45ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242020-02-011446147610.5194/tc-14-461-2020Effects of decimetre-scale surface roughness on L-band brightness temperature of sea iceM. Miernecki0M. Miernecki1L. Kaleschke2L. Kaleschke3N. Maaß4S. Hendricks5S. S. Søbjærg6Institute of Oceanography (IfM), University of Hamburg, Bundesstr. 53, 20146 Hamburg, GermanyCentre d'Etudes Spatiales de la Biosphère (CESBIO), 18 avenue Edouard Belin bpi 2801, 31401 Toulouse CEDEX 9, FranceInstitute of Oceanography (IfM), University of Hamburg, Bundesstr. 53, 20146 Hamburg, GermanyAlfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Bussestr. 24, 27570 Bremerhaven, GermanyInstitute of Oceanography (IfM), University of Hamburg, Bundesstr. 53, 20146 Hamburg, GermanyAlfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Bussestr. 24, 27570 Bremerhaven, GermanyTechnical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark<p>Sea ice thickness is an essential climate variable. Current L-Band sea ice thickness retrieval methods do not account for sea ice surface roughness that is hypothesised to be not relevant to the process. This study attempts to validate this hypothesis that has not been tested yet. To test this hypothesis, we created a physical model of sea ice roughness based on geometrical optics and merged it into the L-band emissivity model of sea ice that is similar to the one used in the operational sea ice thickness retrieval algorithm. The facet description of sea ice surface used in geometrical optics is derived from 2-D surface elevation measurements. Subsequently the new model was tested with <span class="inline-formula"><i>T</i><sub>B</sub></span> measurements performed during the SMOSice 2014 field campaign. Our simulation results corroborate the hypothesis that sea ice surface roughness has a marginal impact on near-nadir <span class="inline-formula"><i>T</i><sub>B</sub></span> (used in the current operational retrieval). We demonstrate that the probability distribution function of surface slopes can be approximated with a parametric function whose single parameter can be used to characterise the degree of roughness. Facet azimuth orientation is isotropic at scales greater than 4.3 km. The simulation results indicate that surface roughness is a minor factor in modelling the sea ice brightness temperature. The change in <span class="inline-formula"><i>T</i><sub>B</sub></span> is most pronounced at incidence angles greater than 40<span class="inline-formula"><sup>∘</sup></span> and can reach up to 8 K for vertical polarisation at 60<span class="inline-formula"><sup>∘</sup></span>. Therefore current and future L-band missions (SMOS, SMAP, CIMR, SMOS-HR) measuring at such angles can be affected. Comparison of the brightness temperature simulations with the SMOSice 2014 radiometer data does not yield definite results.</p>https://www.the-cryosphere.net/14/461/2020/tc-14-461-2020.pdf |
| spellingShingle | M. Miernecki M. Miernecki L. Kaleschke L. Kaleschke N. Maaß S. Hendricks S. S. Søbjærg Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice The Cryosphere |
| title | Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice |
| title_full | Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice |
| title_fullStr | Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice |
| title_full_unstemmed | Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice |
| title_short | Effects of decimetre-scale surface roughness on L-band brightness temperature of sea ice |
| title_sort | effects of decimetre scale surface roughness on l band brightness temperature of sea ice |
| url | https://www.the-cryosphere.net/14/461/2020/tc-14-461-2020.pdf |
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