Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model
peer reviewed 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 coor...
Published in: | Frontiers in Climate |
---|---|
Main Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Frontiers Media S.A.
2022
|
Subjects: | |
Online Access: | https://orbi.uliege.be/handle/2268/299521 https://orbi.uliege.be/bitstream/2268/299521/1/fclim-04-918572.pdf https://doi.org/10.3389/fclim.2022.918572 |
id |
ftorbi:oai:orbi.ulg.ac.be:2268/299521 |
---|---|
record_format |
openpolar |
spelling |
ftorbi:oai:orbi.ulg.ac.be:2268/299521 2024-04-21T08:08:05+00:00 Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model Wang, Yiguo Counillon, François Barthélémy, Sébastien Barth, Alexander 2022-12-15 https://orbi.uliege.be/handle/2268/299521 https://orbi.uliege.be/bitstream/2268/299521/1/fclim-04-918572.pdf https://doi.org/10.3389/fclim.2022.918572 en eng Frontiers Media S.A. https://www.frontiersin.org/articles/10.3389/fclim.2022.918572/full urn:issn:2624-9553 https://orbi.uliege.be/handle/2268/299521 info:hdl:2268/299521 https://orbi.uliege.be/bitstream/2268/299521/1/fclim-04-918572.pdf doi:10.3389/fclim.2022.918572 scopus-id:2-s2.0-85145090700 open access http://purl.org/coar/access_right/c_abf2 info:eu-repo/semantics/openAccess Frontiers in Climate, 4 (2022-12-15) EnKF isopycnal coordinate reanalysis SST assimilation vertical localization Global and Planetary Change Environmental Science (miscellaneous) Pollution Atmospheric Science Management Monitoring Policy and Law Physical chemical mathematical & earth Sciences Earth sciences & physical geography Physique chimie mathématiques & sciences de la terre Sciences de la terre & géographie physique journal article http://purl.org/coar/resource_type/c_6501 info:eu-repo/semantics/article peer reviewed 2022 ftorbi https://doi.org/10.3389/fclim.2022.918572 2024-03-27T14:57:31Z peer reviewed 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 University of Liège: ORBi (Open Repository and Bibliography) Frontiers in Climate 4 |
institution |
Open Polar |
collection |
University of Liège: ORBi (Open Repository and Bibliography) |
op_collection_id |
ftorbi |
language |
English |
topic |
EnKF isopycnal coordinate reanalysis SST assimilation vertical localization Global and Planetary Change Environmental Science (miscellaneous) Pollution Atmospheric Science Management Monitoring Policy and Law Physical chemical mathematical & earth Sciences Earth sciences & physical geography Physique chimie mathématiques & sciences de la terre Sciences de la terre & géographie physique |
spellingShingle |
EnKF isopycnal coordinate reanalysis SST assimilation vertical localization Global and Planetary Change Environmental Science (miscellaneous) Pollution Atmospheric Science Management Monitoring Policy and Law Physical chemical mathematical & earth Sciences Earth sciences & physical geography Physique chimie mathématiques & sciences de la terre Sciences de la terre & géographie physique Wang, Yiguo Counillon, François Barthélémy, Sébastien Barth, Alexander Benefit of vertical localization for sea surface temperature assimilation in isopycnal coordinate model |
topic_facet |
EnKF isopycnal coordinate reanalysis SST assimilation vertical localization Global and Planetary Change Environmental Science (miscellaneous) Pollution Atmospheric Science Management Monitoring Policy and Law Physical chemical mathematical & earth Sciences Earth sciences & physical geography Physique chimie mathématiques & sciences de la terre Sciences de la terre & géographie physique |
description |
peer reviewed 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. |
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 S.A. |
publishDate |
2022 |
url |
https://orbi.uliege.be/handle/2268/299521 https://orbi.uliege.be/bitstream/2268/299521/1/fclim-04-918572.pdf https://doi.org/10.3389/fclim.2022.918572 |
genre |
North Atlantic Southern Ocean |
genre_facet |
North Atlantic Southern Ocean |
op_source |
Frontiers in Climate, 4 (2022-12-15) |
op_relation |
https://www.frontiersin.org/articles/10.3389/fclim.2022.918572/full urn:issn:2624-9553 https://orbi.uliege.be/handle/2268/299521 info:hdl:2268/299521 https://orbi.uliege.be/bitstream/2268/299521/1/fclim-04-918572.pdf doi:10.3389/fclim.2022.918572 scopus-id:2-s2.0-85145090700 |
op_rights |
open access http://purl.org/coar/access_right/c_abf2 info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.3389/fclim.2022.918572 |
container_title |
Frontiers in Climate |
container_volume |
4 |
_version_ |
1796948287554584576 |