Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5
One of the major globally relevant systematic biases in previous generations of climate models has been an equatorward bias in the latitude of the Southern Hemisphere (SH) mid‐latitude tropospheric eddy driven westerly jet. The far reaching implications of this for Southern Ocean heat and carbon upt...
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2020
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Online Access: | https://epic.awi.de/id/eprint/52105/ https://epic.awi.de/id/eprint/52105/1/2019EA001065-2.pdf https://doi.org/10.1029/2019EA001065 https://hdl.handle.net/10013/epic.f8fe4c7c-5074-4cd6-a8fa-fe5587338c30 https://hdl.handle.net/ |
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ftawi:oai:epic.awi.de:52105 2023-05-15T13:24:10+02:00 Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 Bracegirdle, T. J. Holmes, C. R. Hosking, J. S. Marshall, G. J. Osman, M. Patterson, M. Rackow, T. 2020-05-18 application/pdf https://epic.awi.de/id/eprint/52105/ https://epic.awi.de/id/eprint/52105/1/2019EA001065-2.pdf https://doi.org/10.1029/2019EA001065 https://hdl.handle.net/10013/epic.f8fe4c7c-5074-4cd6-a8fa-fe5587338c30 https://hdl.handle.net/ unknown AMER GEOPHYSICAL UNION https://epic.awi.de/id/eprint/52105/1/2019EA001065-2.pdf https://hdl.handle.net/ Bracegirdle, T. J. , Holmes, C. R. , Hosking, J. S. , Marshall, G. J. , Osman, M. , Patterson, M. and Rackow, T. orcid:0000-0002-5468-575X (2020) Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 , Earth and Space Science, 7 (6), e2019EA001065 . doi:10.1029/2019EA001065 <https://doi.org/10.1029/2019EA001065> , hdl:10013/epic.f8fe4c7c-5074-4cd6-a8fa-fe5587338c30 EPIC3Earth and Space Science, AMER GEOPHYSICAL UNION, 7(6), pp. e2019EA001065, ISSN: 2333-5084 Article isiRev 2020 ftawi https://doi.org/10.1029/2019EA001065 2021-12-24T15:45:36Z One of the major globally relevant systematic biases in previous generations of climate models has been an equatorward bias in the latitude of the Southern Hemisphere (SH) mid‐latitude tropospheric eddy driven westerly jet. The far reaching implications of this for Southern Ocean heat and carbon uptake and Antarctic land and sea ice are key reasons why addressing this bias is a high priority. It is therefore of primary importance to evaluate the representation of the SH westerly jet in the latest generation of global climate and earth‐system models that comprise the Coupled Model Intercomparison Project Phase 6 (CMIP6). In this paper we assess the representation of major indices of SH extratropical atmospheric circulation in CMIP6 by comparison against both observations and the previous generation of CMIP5 models. Indices assessed are the latitude and speed of the westerly jet, variability of the Southern Annular Mode (SAM) and representation of the Amundsen Sea Low (ASL). These are calculated from the historical forcing simulations of both CMIP5 and CMIP6 for time periods matching available observational and reanalysis datasets. From the 39 CMIP6 models available at the time of writing there is an overall reduction in the equatorward bias of the annual mean westerly jet from 1.9° in CMIP5 to 0.4° in CMIP6 and from a seasonal perspective the reduction is clearest in austral spring and summer. This is accompanied by a halving of the bias of SAM decorrelation timescales compared to CMIP5. However, no such overall improvements are evident for the ASL. Article in Journal/Newspaper Amundsen Sea Antarc* Antarctic Sea ice Southern Ocean Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Antarctic Southern Ocean Austral Amundsen Sea Earth and Space Science 7 6 |
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Open Polar |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
op_collection_id |
ftawi |
language |
unknown |
description |
One of the major globally relevant systematic biases in previous generations of climate models has been an equatorward bias in the latitude of the Southern Hemisphere (SH) mid‐latitude tropospheric eddy driven westerly jet. The far reaching implications of this for Southern Ocean heat and carbon uptake and Antarctic land and sea ice are key reasons why addressing this bias is a high priority. It is therefore of primary importance to evaluate the representation of the SH westerly jet in the latest generation of global climate and earth‐system models that comprise the Coupled Model Intercomparison Project Phase 6 (CMIP6). In this paper we assess the representation of major indices of SH extratropical atmospheric circulation in CMIP6 by comparison against both observations and the previous generation of CMIP5 models. Indices assessed are the latitude and speed of the westerly jet, variability of the Southern Annular Mode (SAM) and representation of the Amundsen Sea Low (ASL). These are calculated from the historical forcing simulations of both CMIP5 and CMIP6 for time periods matching available observational and reanalysis datasets. From the 39 CMIP6 models available at the time of writing there is an overall reduction in the equatorward bias of the annual mean westerly jet from 1.9° in CMIP5 to 0.4° in CMIP6 and from a seasonal perspective the reduction is clearest in austral spring and summer. This is accompanied by a halving of the bias of SAM decorrelation timescales compared to CMIP5. However, no such overall improvements are evident for the ASL. |
format |
Article in Journal/Newspaper |
author |
Bracegirdle, T. J. Holmes, C. R. Hosking, J. S. Marshall, G. J. Osman, M. Patterson, M. Rackow, T. |
spellingShingle |
Bracegirdle, T. J. Holmes, C. R. Hosking, J. S. Marshall, G. J. Osman, M. Patterson, M. Rackow, T. Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 |
author_facet |
Bracegirdle, T. J. Holmes, C. R. Hosking, J. S. Marshall, G. J. Osman, M. Patterson, M. Rackow, T. |
author_sort |
Bracegirdle, T. J. |
title |
Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 |
title_short |
Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 |
title_full |
Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 |
title_fullStr |
Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 |
title_full_unstemmed |
Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 |
title_sort |
improvements in circumpolar southern hemisphere extratropical atmospheric circulation in cmip6 compared to cmip5 |
publisher |
AMER GEOPHYSICAL UNION |
publishDate |
2020 |
url |
https://epic.awi.de/id/eprint/52105/ https://epic.awi.de/id/eprint/52105/1/2019EA001065-2.pdf https://doi.org/10.1029/2019EA001065 https://hdl.handle.net/10013/epic.f8fe4c7c-5074-4cd6-a8fa-fe5587338c30 https://hdl.handle.net/ |
geographic |
Antarctic Southern Ocean Austral Amundsen Sea |
geographic_facet |
Antarctic Southern Ocean Austral Amundsen Sea |
genre |
Amundsen Sea Antarc* Antarctic Sea ice Southern Ocean |
genre_facet |
Amundsen Sea Antarc* Antarctic Sea ice Southern Ocean |
op_source |
EPIC3Earth and Space Science, AMER GEOPHYSICAL UNION, 7(6), pp. e2019EA001065, ISSN: 2333-5084 |
op_relation |
https://epic.awi.de/id/eprint/52105/1/2019EA001065-2.pdf https://hdl.handle.net/ Bracegirdle, T. J. , Holmes, C. R. , Hosking, J. S. , Marshall, G. J. , Osman, M. , Patterson, M. and Rackow, T. orcid:0000-0002-5468-575X (2020) Improvements in Circumpolar Southern Hemisphere Extratropical Atmospheric Circulation in CMIP6 Compared to CMIP5 , Earth and Space Science, 7 (6), e2019EA001065 . doi:10.1029/2019EA001065 <https://doi.org/10.1029/2019EA001065> , hdl:10013/epic.f8fe4c7c-5074-4cd6-a8fa-fe5587338c30 |
op_doi |
https://doi.org/10.1029/2019EA001065 |
container_title |
Earth and Space Science |
container_volume |
7 |
container_issue |
6 |
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1766377830511280128 |