The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability
This article provides a reconciling perspective on the two main, but contradictory, interpretations of the southern annular mode (SAM). SAM was originally thought to characterize meridional shifts in the storm track across the entire hemisphere. This perspective was later questioned, and SAM was int...
Published in: | Journal of Climate |
---|---|
Main Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
American Meteorological Society
2020
|
Subjects: | |
Online Access: | https://hdl.handle.net/11250/2764624 https://doi.org/10.1175/JCLI-D-19-0224.1 |
id |
ftunivbergen:oai:bora.uib.no:11250/2764624 |
---|---|
record_format |
openpolar |
spelling |
ftunivbergen:oai:bora.uib.no:11250/2764624 2023-05-15T14:02:46+02:00 The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability Spensberger, Clemens Reeder, Michael John Spengler, Thomas Patterson, Matthew 2020 application/pdf https://hdl.handle.net/11250/2764624 https://doi.org/10.1175/JCLI-D-19-0224.1 eng eng American Meteorological Society urn:issn:0894-8755 https://hdl.handle.net/11250/2764624 https://doi.org/10.1175/JCLI-D-19-0224.1 cristin:1757921 Journal of Climate. 2020, 33 (1), 115-129. Copyright 2019 American Meteorological Society Journal of Climate 115-129 33 1 Journal article Peer reviewed 2020 ftunivbergen https://doi.org/10.1175/JCLI-D-19-0224.1 2023-03-14T17:43:14Z This article provides a reconciling perspective on the two main, but contradictory, interpretations of the southern annular mode (SAM). SAM was originally thought to characterize meridional shifts in the storm track across the entire hemisphere. This perspective was later questioned, and SAM was interpreted as a statistical artifact depending on the choice of base region for the principal component analysis. Neither perspective, however, fully describes SAM. We show that SAM cannot be interpreted in terms of midlatitude variability, as SAM merely modulates the most poleward part of the cyclone tracks and only marginally influences the distribution of other weather-related features of the storm track (e.g., position of jet axes and Rossby wave breaking). Instead, SAM emerges as the leading pattern of geopotential variability due to strong correlations of sea level pressure around the Antarctic continent. As SAM correlates strongly both with the pan-Antarctic mean temperature and the meridional heat flux through 65°S, we hypothesize that SAM can be interpreted as a measure of the degree of the (de)coupling between Antarctica and the southern midlatitudes. As an alternative way of characterizing southern midlatitude variability, we seek domains in which the leading EOF patterns of both the geopotential and storm-track features yield a dynamically consistent picture. This approach is successful for the South Pacific. Here the leading variability patterns are closely related to the Pacific–South America pattern and point toward an NAO-like variability. publishedVersion Article in Journal/Newspaper Antarc* Antarctic Antarctica University of Bergen: Bergen Open Research Archive (BORA-UiB) Antarctic Pacific The Antarctic Journal of Climate 33 1 115 129 |
institution |
Open Polar |
collection |
University of Bergen: Bergen Open Research Archive (BORA-UiB) |
op_collection_id |
ftunivbergen |
language |
English |
description |
This article provides a reconciling perspective on the two main, but contradictory, interpretations of the southern annular mode (SAM). SAM was originally thought to characterize meridional shifts in the storm track across the entire hemisphere. This perspective was later questioned, and SAM was interpreted as a statistical artifact depending on the choice of base region for the principal component analysis. Neither perspective, however, fully describes SAM. We show that SAM cannot be interpreted in terms of midlatitude variability, as SAM merely modulates the most poleward part of the cyclone tracks and only marginally influences the distribution of other weather-related features of the storm track (e.g., position of jet axes and Rossby wave breaking). Instead, SAM emerges as the leading pattern of geopotential variability due to strong correlations of sea level pressure around the Antarctic continent. As SAM correlates strongly both with the pan-Antarctic mean temperature and the meridional heat flux through 65°S, we hypothesize that SAM can be interpreted as a measure of the degree of the (de)coupling between Antarctica and the southern midlatitudes. As an alternative way of characterizing southern midlatitude variability, we seek domains in which the leading EOF patterns of both the geopotential and storm-track features yield a dynamically consistent picture. This approach is successful for the South Pacific. Here the leading variability patterns are closely related to the Pacific–South America pattern and point toward an NAO-like variability. publishedVersion |
format |
Article in Journal/Newspaper |
author |
Spensberger, Clemens Reeder, Michael John Spengler, Thomas Patterson, Matthew |
spellingShingle |
Spensberger, Clemens Reeder, Michael John Spengler, Thomas Patterson, Matthew The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability |
author_facet |
Spensberger, Clemens Reeder, Michael John Spengler, Thomas Patterson, Matthew |
author_sort |
Spensberger, Clemens |
title |
The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability |
title_short |
The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability |
title_full |
The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability |
title_fullStr |
The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability |
title_full_unstemmed |
The connection between the Southern Annular Mode and a feature-based perspective on Southern Hemisphere mid-latitude winter variability |
title_sort |
connection between the southern annular mode and a feature-based perspective on southern hemisphere mid-latitude winter variability |
publisher |
American Meteorological Society |
publishDate |
2020 |
url |
https://hdl.handle.net/11250/2764624 https://doi.org/10.1175/JCLI-D-19-0224.1 |
geographic |
Antarctic Pacific The Antarctic |
geographic_facet |
Antarctic Pacific The Antarctic |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_source |
Journal of Climate 115-129 33 1 |
op_relation |
urn:issn:0894-8755 https://hdl.handle.net/11250/2764624 https://doi.org/10.1175/JCLI-D-19-0224.1 cristin:1757921 Journal of Climate. 2020, 33 (1), 115-129. |
op_rights |
Copyright 2019 American Meteorological Society |
op_doi |
https://doi.org/10.1175/JCLI-D-19-0224.1 |
container_title |
Journal of Climate |
container_volume |
33 |
container_issue |
1 |
container_start_page |
115 |
op_container_end_page |
129 |
_version_ |
1766273182656888832 |