A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean
Sea-surface temperature (SST) and sea-surface height (SSH) data are assimilated with a reduced-order sequential filter every 10 days over four years (1993-1996) in a 1/3-degree resolution South Atlantic primitive equation model. At every assimilation step, the misfit between observations and their m...
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Online Access: | https://hal.science/hal-00230241 https://doi.org/10.1357/002224002321505147 |
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ftunigrenoble:oai:HAL:hal-00230241v1 2024-05-12T08:11:06+00:00 A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean Penduff, Thierry Brasseur, Pierre Testut, Charles-Emmanuel Barnier, Bernard Verron, Jacques Laboratoire des Écoulements Géophysiques et Industriels Grenoble (LEGI) Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS) Nice, France 2003 https://hal.science/hal-00230241 https://doi.org/10.1357/002224002321505147 en eng HAL CCSD info:eu-repo/semantics/altIdentifier/doi/10.1357/002224002321505147 hal-00230241 https://hal.science/hal-00230241 doi:10.1357/002224002321505147 http://creativecommons.org/licenses/by/ EGS Conference https://hal.science/hal-00230241 EGS Conference, 2003, Nice, France. ⟨10.1357/002224002321505147⟩ [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] info:eu-repo/semantics/conferenceObject Conference papers 2003 ftunigrenoble https://doi.org/10.1357/002224002321505147 2024-04-18T03:41:05Z Sea-surface temperature (SST) and sea-surface height (SSH) data are assimilated with a reduced-order sequential filter every 10 days over four years (1993-1996) in a 1/3-degree resolution South Atlantic primitive equation model. At every assimilation step, the misfit between observations and their model counterparts is evaluated and projected onto the dominant 10 multivariate, full-depth local modes of variability diagnosed from a free model run (without assimilation). Satellite observations are used to perform a sequential update of all model variables according to their "natural" correlations with the surface variables. In this paper, we perform a validation of both the mean state and the eddy flow. Over the four years of assimilation, the forecast-data RMS misfit is decreased (i) by 55% on SSH; (ii) by 40% on SST; (iii) by about 20% on temperature in the upper 700 m with regard to independent, synoptic XBT data; (iv) as deep as 3500 m on the time-averaged temperature distribution compared to a recent climatology. These statistical estimates of the assimilation performance were complemented by a more original oceanographic investigation that revealed a significant improvement in the mean circulation (in particular in the Confluence region and in the deep ocean), the position of the main fronts, the averaged level and basin-scale distribution of SSH variance, the detailed evolution of individual mesoscale structures, the vertical distribution of the eddy kinetic energy, and the salinity field. These results would further be improved by the assimilation of in-situ data below sharp thermoclines that tend to decorrelate subsurface dynamics from the observed surface. Conference Object South Atlantic Ocean Université Grenoble Alpes: HAL Journal of Marine Research 60 6 805 833 |
institution |
Open Polar |
collection |
Université Grenoble Alpes: HAL |
op_collection_id |
ftunigrenoble |
language |
English |
topic |
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] |
spellingShingle |
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] Penduff, Thierry Brasseur, Pierre Testut, Charles-Emmanuel Barnier, Bernard Verron, Jacques A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean |
topic_facet |
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] |
description |
Sea-surface temperature (SST) and sea-surface height (SSH) data are assimilated with a reduced-order sequential filter every 10 days over four years (1993-1996) in a 1/3-degree resolution South Atlantic primitive equation model. At every assimilation step, the misfit between observations and their model counterparts is evaluated and projected onto the dominant 10 multivariate, full-depth local modes of variability diagnosed from a free model run (without assimilation). Satellite observations are used to perform a sequential update of all model variables according to their "natural" correlations with the surface variables. In this paper, we perform a validation of both the mean state and the eddy flow. Over the four years of assimilation, the forecast-data RMS misfit is decreased (i) by 55% on SSH; (ii) by 40% on SST; (iii) by about 20% on temperature in the upper 700 m with regard to independent, synoptic XBT data; (iv) as deep as 3500 m on the time-averaged temperature distribution compared to a recent climatology. These statistical estimates of the assimilation performance were complemented by a more original oceanographic investigation that revealed a significant improvement in the mean circulation (in particular in the Confluence region and in the deep ocean), the position of the main fronts, the averaged level and basin-scale distribution of SSH variance, the detailed evolution of individual mesoscale structures, the vertical distribution of the eddy kinetic energy, and the salinity field. These results would further be improved by the assimilation of in-situ data below sharp thermoclines that tend to decorrelate subsurface dynamics from the observed surface. |
author2 |
Laboratoire des Écoulements Géophysiques et Industriels Grenoble (LEGI) Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS) |
format |
Conference Object |
author |
Penduff, Thierry Brasseur, Pierre Testut, Charles-Emmanuel Barnier, Bernard Verron, Jacques |
author_facet |
Penduff, Thierry Brasseur, Pierre Testut, Charles-Emmanuel Barnier, Bernard Verron, Jacques |
author_sort |
Penduff, Thierry |
title |
A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean |
title_short |
A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean |
title_full |
A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean |
title_fullStr |
A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean |
title_full_unstemmed |
A four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the South Atlantic Ocean |
title_sort |
four-year eddy-permitting assimilation of altimetric and sea-surface temperature data in the south atlantic ocean |
publisher |
HAL CCSD |
publishDate |
2003 |
url |
https://hal.science/hal-00230241 https://doi.org/10.1357/002224002321505147 |
op_coverage |
Nice, France |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_source |
EGS Conference https://hal.science/hal-00230241 EGS Conference, 2003, Nice, France. ⟨10.1357/002224002321505147⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1357/002224002321505147 hal-00230241 https://hal.science/hal-00230241 doi:10.1357/002224002321505147 |
op_rights |
http://creativecommons.org/licenses/by/ |
op_doi |
https://doi.org/10.1357/002224002321505147 |
container_title |
Journal of Marine Research |
container_volume |
60 |
container_issue |
6 |
container_start_page |
805 |
op_container_end_page |
833 |
_version_ |
1798854710913925120 |