Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography
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...
Published in: | Journal of Climate |
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Language: | English |
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American Meteorological Society
2020
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Online Access: | http://nora.nerc.ac.uk/id/eprint/528557/ https://nora.nerc.ac.uk/id/eprint/528557/1/%5B15200442%20-%20Journal%20of%20Climate%5D%20Wintertime%20Southern%20Hemisphere%20Jet%20Streams%20Shaped%20by%20Interaction%20of%20Transient%20Eddies%20with%20Antarctic%20Orography.pdf https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-20-0153.1/354750 |
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ftnerc:oai:nora.nerc.ac.uk:528557 2023-05-15T13:41:45+02:00 Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography Patterson, Matthew Woollings, Tim Bracegirdle, Thomas Lewis, Neil T. 2020-12-15 text http://nora.nerc.ac.uk/id/eprint/528557/ https://nora.nerc.ac.uk/id/eprint/528557/1/%5B15200442%20-%20Journal%20of%20Climate%5D%20Wintertime%20Southern%20Hemisphere%20Jet%20Streams%20Shaped%20by%20Interaction%20of%20Transient%20Eddies%20with%20Antarctic%20Orography.pdf https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-20-0153.1/354750 en eng American Meteorological Society https://nora.nerc.ac.uk/id/eprint/528557/1/%5B15200442%20-%20Journal%20of%20Climate%5D%20Wintertime%20Southern%20Hemisphere%20Jet%20Streams%20Shaped%20by%20Interaction%20of%20Transient%20Eddies%20with%20Antarctic%20Orography.pdf Patterson, Matthew; Woollings, Tim; Bracegirdle, Thomas orcid:0000-0002-8868-4739 Lewis, Neil T. 2020 Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography. Journal of Climate, 33 (24). 10505-10522. https://doi.org/10.1175/JCLI-D-20-0153.1 <https://doi.org/10.1175/JCLI-D-20-0153.1> Publication - Article PeerReviewed 2020 ftnerc https://doi.org/10.1175/JCLI-D-20-0153.1 2023-02-04T19:51:07Z 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 mid-latitude 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 mid-latitude 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 favourable. 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 further polewards, 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 mid-latitudes. Instead, we invoke a simple barotropic mechanism in which the orographic slope creates an effective potential vorticity gradient which alters the eddy momentum flux. Article in Journal/Newspaper Antarc* Antarctic Antarctica East Antarctica Sea ice Natural Environment Research Council: NERC Open Research Archive Antarctic East Antarctica Pacific Indian Journal of Climate 33 24 10505 10522 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
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 mid-latitude 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 mid-latitude 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 favourable. 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 further polewards, 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 mid-latitudes. Instead, we invoke a simple barotropic mechanism in which the orographic slope creates an effective potential vorticity gradient which alters the eddy momentum flux. |
format |
Article in Journal/Newspaper |
author |
Patterson, Matthew Woollings, Tim Bracegirdle, Thomas Lewis, Neil T. |
spellingShingle |
Patterson, Matthew Woollings, Tim Bracegirdle, Thomas Lewis, Neil T. Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography |
author_facet |
Patterson, Matthew Woollings, Tim Bracegirdle, Thomas Lewis, Neil T. |
author_sort |
Patterson, Matthew |
title |
Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography |
title_short |
Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography |
title_full |
Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography |
title_fullStr |
Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography |
title_full_unstemmed |
Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography |
title_sort |
wintertime southern hemisphere jet streams shaped by interaction of transient eddies with antarctic orography |
publisher |
American Meteorological Society |
publishDate |
2020 |
url |
http://nora.nerc.ac.uk/id/eprint/528557/ https://nora.nerc.ac.uk/id/eprint/528557/1/%5B15200442%20-%20Journal%20of%20Climate%5D%20Wintertime%20Southern%20Hemisphere%20Jet%20Streams%20Shaped%20by%20Interaction%20of%20Transient%20Eddies%20with%20Antarctic%20Orography.pdf https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-20-0153.1/354750 |
geographic |
Antarctic East Antarctica Pacific Indian |
geographic_facet |
Antarctic East Antarctica Pacific Indian |
genre |
Antarc* Antarctic Antarctica East Antarctica Sea ice |
genre_facet |
Antarc* Antarctic Antarctica East Antarctica Sea ice |
op_relation |
https://nora.nerc.ac.uk/id/eprint/528557/1/%5B15200442%20-%20Journal%20of%20Climate%5D%20Wintertime%20Southern%20Hemisphere%20Jet%20Streams%20Shaped%20by%20Interaction%20of%20Transient%20Eddies%20with%20Antarctic%20Orography.pdf Patterson, Matthew; Woollings, Tim; Bracegirdle, Thomas orcid:0000-0002-8868-4739 Lewis, Neil T. 2020 Wintertime Southern Hemisphere jet streams shaped by interaction of transient eddies with Antarctic orography. Journal of Climate, 33 (24). 10505-10522. https://doi.org/10.1175/JCLI-D-20-0153.1 <https://doi.org/10.1175/JCLI-D-20-0153.1> |
op_doi |
https://doi.org/10.1175/JCLI-D-20-0153.1 |
container_title |
Journal of Climate |
container_volume |
33 |
container_issue |
24 |
container_start_page |
10505 |
op_container_end_page |
10522 |
_version_ |
1766157060334944256 |