Journal article
Improvements in circumpolar southern hemisphere extratropical atmospheric circulation in CMIP6 compared to CMIP
- Abstract:
- 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.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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- Files:
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(Preview, Accepted manuscript, 1.1MB, Terms of use)
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- Publisher copy:
- 10.1029/2019ea001065
Authors
- Publisher:
- American Geophysical Union
- Journal:
- Earth and Space Science More from this journal
- Publication date:
- 2020-05-18
- Acceptance date:
- 2020-04-23
- DOI:
- EISSN:
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2333-5084
- Language:
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English
- Keywords:
- Pubs id:
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1107553
- Local pid:
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pubs:1107553
- Deposit date:
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2020-05-29
Terms of use
- Copyright holder:
- American Geophysical Union. All rights reserved.
- Copyright date:
- 2020
- Rights statement:
- © 2020 American Geophysical Union. All rights reserved. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
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