Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013
Long dynamical atmospheric reanalyses are widely used for climate studies, but data-assimilative reanalyses of ocean and sea ice in the Arctic are less common. TOPAZ4 is a coupled ocean and sea ice data assimilation system for the North Atlantic and the Arctic that is based on the HYCOM ocean model...
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ftdoajarticles:oai:doaj.org/article:ecd177123be84bfe977c375296763575 2023-05-15T14:48:23+02:00 Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 J. Xie L. Bertino F. Counillon K. A. Lisæter P. Sakov 2017-02-01T00:00:00Z https://doi.org/10.5194/os-13-123-2017 https://doaj.org/article/ecd177123be84bfe977c375296763575 EN eng Copernicus Publications http://www.ocean-sci.net/13/123/2017/os-13-123-2017.pdf https://doaj.org/toc/1812-0784 https://doaj.org/toc/1812-0792 1812-0784 1812-0792 doi:10.5194/os-13-123-2017 https://doaj.org/article/ecd177123be84bfe977c375296763575 Ocean Science, Vol 13, Iss 1, Pp 123-144 (2017) Geography. Anthropology. Recreation G Environmental sciences GE1-350 article 2017 ftdoajarticles https://doi.org/10.5194/os-13-123-2017 2022-12-31T13:00:43Z Long dynamical atmospheric reanalyses are widely used for climate studies, but data-assimilative reanalyses of ocean and sea ice in the Arctic are less common. TOPAZ4 is a coupled ocean and sea ice data assimilation system for the North Atlantic and the Arctic that is based on the HYCOM ocean model and the ensemble Kalman filter data assimilation method using 100 dynamical members. A 23-year reanalysis has been completed for the period 1991–2013 and is the multi-year physical product in the Copernicus Marine Environment Monitoring Service (CMEMS) Arctic Marine Forecasting Center (ARC MFC). This study presents its quantitative quality assessment, compared to both assimilated and unassimilated observations available in the whole Arctic region, in order to document the strengths and weaknesses of the system for potential users. It is found that TOPAZ4 performs well with respect to near-surface ocean variables, but some limitations appear in the interior of the ocean and for ice thickness, where observations are sparse. In the course of the reanalysis, the skills of the system are improving as the observation network becomes denser, in particular during the International Polar Year. The online bias estimation successfully maintains a low bias in our system. In addition, statistics of the reduced centered random variables (RCRVs) confirm the reliability of the ensemble for most of the assimilated variables. Occasional discontinuities of these statistics are caused by the changes of the input data sets or the data assimilation settings, but the statistics remain otherwise stable throughout the reanalysis, regardless of the density of observations. Furthermore, no data type is severely less dispersed than the others, even though the lack of consistently reprocessed observation time series at the beginning of the reanalysis has proven challenging. Article in Journal/Newspaper Arctic International Polar Year North Atlantic Sea ice Directory of Open Access Journals: DOAJ Articles Arctic Ocean Science 13 1 123 144 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Geography. Anthropology. Recreation G Environmental sciences GE1-350 |
spellingShingle |
Geography. Anthropology. Recreation G Environmental sciences GE1-350 J. Xie L. Bertino F. Counillon K. A. Lisæter P. Sakov Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 |
topic_facet |
Geography. Anthropology. Recreation G Environmental sciences GE1-350 |
description |
Long dynamical atmospheric reanalyses are widely used for climate studies, but data-assimilative reanalyses of ocean and sea ice in the Arctic are less common. TOPAZ4 is a coupled ocean and sea ice data assimilation system for the North Atlantic and the Arctic that is based on the HYCOM ocean model and the ensemble Kalman filter data assimilation method using 100 dynamical members. A 23-year reanalysis has been completed for the period 1991–2013 and is the multi-year physical product in the Copernicus Marine Environment Monitoring Service (CMEMS) Arctic Marine Forecasting Center (ARC MFC). This study presents its quantitative quality assessment, compared to both assimilated and unassimilated observations available in the whole Arctic region, in order to document the strengths and weaknesses of the system for potential users. It is found that TOPAZ4 performs well with respect to near-surface ocean variables, but some limitations appear in the interior of the ocean and for ice thickness, where observations are sparse. In the course of the reanalysis, the skills of the system are improving as the observation network becomes denser, in particular during the International Polar Year. The online bias estimation successfully maintains a low bias in our system. In addition, statistics of the reduced centered random variables (RCRVs) confirm the reliability of the ensemble for most of the assimilated variables. Occasional discontinuities of these statistics are caused by the changes of the input data sets or the data assimilation settings, but the statistics remain otherwise stable throughout the reanalysis, regardless of the density of observations. Furthermore, no data type is severely less dispersed than the others, even though the lack of consistently reprocessed observation time series at the beginning of the reanalysis has proven challenging. |
format |
Article in Journal/Newspaper |
author |
J. Xie L. Bertino F. Counillon K. A. Lisæter P. Sakov |
author_facet |
J. Xie L. Bertino F. Counillon K. A. Lisæter P. Sakov |
author_sort |
J. Xie |
title |
Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 |
title_short |
Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 |
title_full |
Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 |
title_fullStr |
Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 |
title_full_unstemmed |
Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 |
title_sort |
quality assessment of the topaz4 reanalysis in the arctic over the period 1991–2013 |
publisher |
Copernicus Publications |
publishDate |
2017 |
url |
https://doi.org/10.5194/os-13-123-2017 https://doaj.org/article/ecd177123be84bfe977c375296763575 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic International Polar Year North Atlantic Sea ice |
genre_facet |
Arctic International Polar Year North Atlantic Sea ice |
op_source |
Ocean Science, Vol 13, Iss 1, Pp 123-144 (2017) |
op_relation |
http://www.ocean-sci.net/13/123/2017/os-13-123-2017.pdf https://doaj.org/toc/1812-0784 https://doaj.org/toc/1812-0792 1812-0784 1812-0792 doi:10.5194/os-13-123-2017 https://doaj.org/article/ecd177123be84bfe977c375296763575 |
op_doi |
https://doi.org/10.5194/os-13-123-2017 |
container_title |
Ocean Science |
container_volume |
13 |
container_issue |
1 |
container_start_page |
123 |
op_container_end_page |
144 |
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