The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment
The ECMWF OCEAN5 system is a global ocean and sea-ice ensemble of reanalysis and real-time analysis. This paper gives a full description of the OCEAN5 system, with the focus on upgrades of system components with respect to its predecessors, ORAS4 and ORAP5. An important novelty in OCEAN5 is the ense...
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ftcopernicus:oai:publications.copernicus.org:os73600 2023-05-15T18:17:05+02:00 The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment Zuo, Hao Balmaseda, Magdalena Alonso Tietsche, Steffen Mogensen, Kristian Mayer, Michael 2019-06-20 application/pdf https://doi.org/10.5194/os-15-779-2019 https://os.copernicus.org/articles/15/779/2019/ eng eng doi:10.5194/os-15-779-2019 https://os.copernicus.org/articles/15/779/2019/ eISSN: 1812-0792 Text 2019 ftcopernicus https://doi.org/10.5194/os-15-779-2019 2020-07-20T16:22:47Z The ECMWF OCEAN5 system is a global ocean and sea-ice ensemble of reanalysis and real-time analysis. This paper gives a full description of the OCEAN5 system, with the focus on upgrades of system components with respect to its predecessors, ORAS4 and ORAP5. An important novelty in OCEAN5 is the ensemble generation strategy that includes perturbation of initial conditions and a generic perturbation scheme for observations and forcing fields. Other upgrades include revisions to the a priori bias correction scheme, observation quality control and assimilation method for sea-level anomalies. The OCEAN5 historical reconstruction of the ocean and sea-ice state is the ORAS5 reanalysis, which includes five ensemble members and covers the period from 1979 onwards. Updated versions of observation data sets are used in ORAS5 production, with special attention devoted to the consistency of sea surface temperature (SST) and sea-ice observations. Assessment of ORAS5 through sensitivity experiments suggests that all system components contribute to an improved fit to observation in reanalyses, with the most prominent contribution from direct assimilation of ocean in situ observations. Results of observing system experiments further suggest that the Argo float is the most influential observation type in our data assimilation system. Assessment of ORAS5 has also been carried out for several key ocean state variables and verified against reference climate data sets from the ESA CCI (European Space Agency Climate Change Initiative) project. With respect to ORAS4, ORAS5 has improved ocean climate state and variability in terms of SST and sea level, mostly due to increased model resolution and updates in assimilated observation data sets. In spite of the improvements, ORAS5 still underestimates the temporal variance of sea level and continues exhibiting large SST biases in the Gulf Stream and its extension regions which are possibly associated with misrepresentation of front positions. Overall, the SST and sea-ice uncertainties estimated using five ORAS5 ensemble members have spatial patterns consistent with those of analysis error. The ensemble spread of sea ice is commensurable with the sea-ice analysis error. On the contrary, the ensemble spread is under-dispersive for SST. Text Sea ice Copernicus Publications: E-Journals Ocean Science 15 3 779 808 |
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Copernicus Publications: E-Journals |
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ftcopernicus |
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English |
description |
The ECMWF OCEAN5 system is a global ocean and sea-ice ensemble of reanalysis and real-time analysis. This paper gives a full description of the OCEAN5 system, with the focus on upgrades of system components with respect to its predecessors, ORAS4 and ORAP5. An important novelty in OCEAN5 is the ensemble generation strategy that includes perturbation of initial conditions and a generic perturbation scheme for observations and forcing fields. Other upgrades include revisions to the a priori bias correction scheme, observation quality control and assimilation method for sea-level anomalies. The OCEAN5 historical reconstruction of the ocean and sea-ice state is the ORAS5 reanalysis, which includes five ensemble members and covers the period from 1979 onwards. Updated versions of observation data sets are used in ORAS5 production, with special attention devoted to the consistency of sea surface temperature (SST) and sea-ice observations. Assessment of ORAS5 through sensitivity experiments suggests that all system components contribute to an improved fit to observation in reanalyses, with the most prominent contribution from direct assimilation of ocean in situ observations. Results of observing system experiments further suggest that the Argo float is the most influential observation type in our data assimilation system. Assessment of ORAS5 has also been carried out for several key ocean state variables and verified against reference climate data sets from the ESA CCI (European Space Agency Climate Change Initiative) project. With respect to ORAS4, ORAS5 has improved ocean climate state and variability in terms of SST and sea level, mostly due to increased model resolution and updates in assimilated observation data sets. In spite of the improvements, ORAS5 still underestimates the temporal variance of sea level and continues exhibiting large SST biases in the Gulf Stream and its extension regions which are possibly associated with misrepresentation of front positions. Overall, the SST and sea-ice uncertainties estimated using five ORAS5 ensemble members have spatial patterns consistent with those of analysis error. The ensemble spread of sea ice is commensurable with the sea-ice analysis error. On the contrary, the ensemble spread is under-dispersive for SST. |
format |
Text |
author |
Zuo, Hao Balmaseda, Magdalena Alonso Tietsche, Steffen Mogensen, Kristian Mayer, Michael |
spellingShingle |
Zuo, Hao Balmaseda, Magdalena Alonso Tietsche, Steffen Mogensen, Kristian Mayer, Michael The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
author_facet |
Zuo, Hao Balmaseda, Magdalena Alonso Tietsche, Steffen Mogensen, Kristian Mayer, Michael |
author_sort |
Zuo, Hao |
title |
The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
title_short |
The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
title_full |
The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
title_fullStr |
The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
title_full_unstemmed |
The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
title_sort |
ecmwf operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment |
publishDate |
2019 |
url |
https://doi.org/10.5194/os-15-779-2019 https://os.copernicus.org/articles/15/779/2019/ |
genre |
Sea ice |
genre_facet |
Sea ice |
op_source |
eISSN: 1812-0792 |
op_relation |
doi:10.5194/os-15-779-2019 https://os.copernicus.org/articles/15/779/2019/ |
op_doi |
https://doi.org/10.5194/os-15-779-2019 |
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Ocean Science |
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15 |
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3 |
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779 |
op_container_end_page |
808 |
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