Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model
Sea surface temperature (SST) observations are a critical data set for long-term climate reconstruction. However, their assimilation with an ensemble-based data assimilation method can degrade performance in the ocean interior due to spurious covariances. Assimilation in isopycnal coordinates can de...
Published in: | Frontiers in Climate |
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Online Access: | http://dx.doi.org/10.3389/fclim.2022.918572 https://www.frontiersin.org/articles/10.3389/fclim.2022.918572/full |
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crfrontiers:10.3389/fclim.2022.918572 2024-02-11T10:06:39+01:00 Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model Wang, Yiguo Counillon, François Barthélémy, Sébastien Barth, Alexander Norges Forskningsråd Trond Mohn stiftelse 2022 http://dx.doi.org/10.3389/fclim.2022.918572 https://www.frontiersin.org/articles/10.3389/fclim.2022.918572/full unknown Frontiers Media SA https://creativecommons.org/licenses/by/4.0/ Frontiers in Climate volume 4 ISSN 2624-9553 Management, Monitoring, Policy and Law Atmospheric Science Pollution Environmental Science (miscellaneous) Global and Planetary Change journal-article 2022 crfrontiers https://doi.org/10.3389/fclim.2022.918572 2024-01-26T10:06:18Z Sea surface temperature (SST) observations are a critical data set for long-term climate reconstruction. However, their assimilation with an ensemble-based data assimilation method can degrade performance in the ocean interior due to spurious covariances. Assimilation in isopycnal coordinates can delay the degradation, but it remains problematic for long reanalysis. We introduce vertical localization for SST assimilation in the isopycnal coordinate. The tapering functions are formulated empirically from a large pre-industrial ensemble. We propose three schemes: 1) a step function with a small localization radius that updates layers from the surface down to the first layer for which insignificant correlation with SST is found, 2) a step function with a large localization radius that updates layers down to the last layer for which significant correlation with SST is found, and 3) a flattop smooth tapering function. These tapering functions vary spatially and with the calendar month and are applied to isopycnal temperature and salinity. The impact of vertical localization on reanalysis performance is tested in identical twin experiments within the Norwegian Climate Prediction Model (NorCPM) with SST assimilation over the period 1980–2010. The SST assimilation without vertical localization greatly enhances performance in the whole water column but introduces a weak degradation at intermediate depths (e.g., 2,000–4,000 m). Vertical localization greatly reduces the degradation and improves the overall accuracy of the reanalysis, in particular in the North Pacific and the North Atlantic. A weak degradation remains in some regions below 2,000 m in the Southern Ocean. Among the three schemes, scheme 2) outperforms schemes 1) and 3) for temperature and salinity. Article in Journal/Newspaper North Atlantic Southern Ocean Frontiers (Publisher) Pacific Southern Ocean Frontiers in Climate 4 |
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Open Polar |
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Frontiers (Publisher) |
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language |
unknown |
topic |
Management, Monitoring, Policy and Law Atmospheric Science Pollution Environmental Science (miscellaneous) Global and Planetary Change |
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Management, Monitoring, Policy and Law Atmospheric Science Pollution Environmental Science (miscellaneous) Global and Planetary Change Wang, Yiguo Counillon, François Barthélémy, Sébastien Barth, Alexander Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
topic_facet |
Management, Monitoring, Policy and Law Atmospheric Science Pollution Environmental Science (miscellaneous) Global and Planetary Change |
description |
Sea surface temperature (SST) observations are a critical data set for long-term climate reconstruction. However, their assimilation with an ensemble-based data assimilation method can degrade performance in the ocean interior due to spurious covariances. Assimilation in isopycnal coordinates can delay the degradation, but it remains problematic for long reanalysis. We introduce vertical localization for SST assimilation in the isopycnal coordinate. The tapering functions are formulated empirically from a large pre-industrial ensemble. We propose three schemes: 1) a step function with a small localization radius that updates layers from the surface down to the first layer for which insignificant correlation with SST is found, 2) a step function with a large localization radius that updates layers down to the last layer for which significant correlation with SST is found, and 3) a flattop smooth tapering function. These tapering functions vary spatially and with the calendar month and are applied to isopycnal temperature and salinity. The impact of vertical localization on reanalysis performance is tested in identical twin experiments within the Norwegian Climate Prediction Model (NorCPM) with SST assimilation over the period 1980–2010. The SST assimilation without vertical localization greatly enhances performance in the whole water column but introduces a weak degradation at intermediate depths (e.g., 2,000–4,000 m). Vertical localization greatly reduces the degradation and improves the overall accuracy of the reanalysis, in particular in the North Pacific and the North Atlantic. A weak degradation remains in some regions below 2,000 m in the Southern Ocean. Among the three schemes, scheme 2) outperforms schemes 1) and 3) for temperature and salinity. |
author2 |
Norges Forskningsråd Trond Mohn stiftelse |
format |
Article in Journal/Newspaper |
author |
Wang, Yiguo Counillon, François Barthélémy, Sébastien Barth, Alexander |
author_facet |
Wang, Yiguo Counillon, François Barthélémy, Sébastien Barth, Alexander |
author_sort |
Wang, Yiguo |
title |
Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
title_short |
Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
title_full |
Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
title_fullStr |
Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
title_full_unstemmed |
Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
title_sort |
benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
publisher |
Frontiers Media SA |
publishDate |
2022 |
url |
http://dx.doi.org/10.3389/fclim.2022.918572 https://www.frontiersin.org/articles/10.3389/fclim.2022.918572/full |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
North Atlantic Southern Ocean |
genre_facet |
North Atlantic Southern Ocean |
op_source |
Frontiers in Climate volume 4 ISSN 2624-9553 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3389/fclim.2022.918572 |
container_title |
Frontiers in Climate |
container_volume |
4 |
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1790604489954164736 |