Journal article
Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography
- Abstract:
- The wintertime Southern Hemisphere extratropical circulation exhibits considerable zonal asymmetries. We investigate the roles of various surface boundary conditions in shaping the mean state using a semi-realistic, atmosphere-only climate model. We find, in agreement with previous literature, that tropical sea surface temperature (SST) patterns are an important contributor to the mean state, while midlatitude SSTs and sea ice extent play a smaller role. Our main finding is that Antarctic orography has a first-order effect on the structure of the midlatitude circulation. In the absence of Antarctic orography, equatorward eddy momentum fluxes associated with the orography are removed and hence convergence of eddy momentum in midlatitudes is reduced. This weakens the Indian Ocean jet, making Rossby wave propagation downstream to the South Pacific less favorable. Consequently, the flow stagnates over the mid- to high-latitude South Pacific and the characteristic split jet pattern is destroyed. Removing Antarctic orography also results in a substantial warming over East Antarctica partly because transient eddies are able to penetrate farther poleward, enhancing poleward heat transport. However, experiments in which a high-latitude cooling is applied indicate that these temperature changes are not the primary driver of circulation changes in the midlatitudes. Instead, we invoke a simple barotropic mechanism in which the orographic slope creates an effective potential vorticity gradient that alters the eddy momentum flux.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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Access Document
- Files:
-
-
(Preview, Accepted manuscript, 6.7MB, Terms of use)
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- Publisher copy:
- 10.1175/JCLI-D-20-0153.1
Authors
- Publisher:
- Wiley
- Journal:
- Journal of Climate More from this journal
- Volume:
- 33
- Issue:
- 24
- Pages:
- 10505–10522
- Publication date:
- 2020-11-16
- Acceptance date:
- 2020-09-14
- DOI:
- EISSN:
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1520-0442
- ISSN:
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0894-8755
- Language:
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English
- Keywords:
- Pubs id:
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1132257
- Local pid:
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pubs:1132257
- Deposit date:
-
2020-09-15
Terms of use
- Copyright holder:
- AMS
- Copyright date:
- 2020
- Rights statement:
- © AMS 2020
- Notes:
- This is the accepted manuscript version of the article. The final version is available from Wiley at: https://doi.org/10.1175/JCLI-D-20-0153.1
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