Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex
The wintertime stratospheric westerly winds circling the Antarctic continent, also known as the Southern Hemisphere polar vortex, create a barrier to mixing of air between middle and high latitudes. This dynamical isolation has important consequences for export of ozone-depleted air from the Antarct...
Published in: | Atmospheric Chemistry and Physics |
---|---|
Main Authors: | , , |
Format: | Text |
Language: | English |
Published: |
2019
|
Subjects: | |
Online Access: | https://doi.org/10.5194/acp-18-8065-2018 https://www.atmos-chem-phys.net/18/8065/2018/ |
id |
ftcopernicus:oai:publications.copernicus.org:acp62954 |
---|---|
record_format |
openpolar |
spelling |
ftcopernicus:oai:publications.copernicus.org:acp62954 2023-05-15T13:35:06+02:00 Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex Conway, Jonathan Bodeker, Greg Cameron, Chris 2019-02-13 application/pdf https://doi.org/10.5194/acp-18-8065-2018 https://www.atmos-chem-phys.net/18/8065/2018/ eng eng doi:10.5194/acp-18-8065-2018 https://www.atmos-chem-phys.net/18/8065/2018/ eISSN: 1680-7324 Text 2019 ftcopernicus https://doi.org/10.5194/acp-18-8065-2018 2019-12-24T09:50:09Z The wintertime stratospheric westerly winds circling the Antarctic continent, also known as the Southern Hemisphere polar vortex, create a barrier to mixing of air between middle and high latitudes. This dynamical isolation has important consequences for export of ozone-depleted air from the Antarctic stratosphere to lower latitudes. The prevailing view of this dynamical barrier has been an annulus compromising steep gradients of potential vorticity (PV) that create a single semi-permeable barrier to mixing. Analyses presented here show that this barrier often displays a bifurcated structure where a double-walled barrier exists. The bifurcated structure manifests as enhanced gradients of PV at two distinct latitudes – usually on the inside and outside flanks of the region of highest wind speed. Metrics that quantify the bifurcated nature of the vortex have been developed and their variation in space and time has been analysed. At most isentropic levels between 395 and 850 K, bifurcation is strongest in mid-winter and decreases dramatically during spring. From August onwards a distinct structure emerges, where elevated bifurcation remains between 475 and 600 K, and a mostly single-walled barrier occurs at other levels. While bifurcation at a given level evolves from month to month, and does not always persist through a season, interannual variations in the strength of bifurcation display coherence across multiple levels in any given month. Accounting for bifurcation allows the region of reduced mixing to be better characterised. These results suggest that improved understanding of cross-vortex mixing requires consideration of the polar vortex not as a single mixing barrier but as a barrier with internal structure that is likely to manifest as more complex gradients in trace gas concentrations across the vortex barrier region. Text Antarc* Antarctic Copernicus Publications: E-Journals Antarctic The Antarctic Atmospheric Chemistry and Physics 18 11 8065 8077 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
The wintertime stratospheric westerly winds circling the Antarctic continent, also known as the Southern Hemisphere polar vortex, create a barrier to mixing of air between middle and high latitudes. This dynamical isolation has important consequences for export of ozone-depleted air from the Antarctic stratosphere to lower latitudes. The prevailing view of this dynamical barrier has been an annulus compromising steep gradients of potential vorticity (PV) that create a single semi-permeable barrier to mixing. Analyses presented here show that this barrier often displays a bifurcated structure where a double-walled barrier exists. The bifurcated structure manifests as enhanced gradients of PV at two distinct latitudes – usually on the inside and outside flanks of the region of highest wind speed. Metrics that quantify the bifurcated nature of the vortex have been developed and their variation in space and time has been analysed. At most isentropic levels between 395 and 850 K, bifurcation is strongest in mid-winter and decreases dramatically during spring. From August onwards a distinct structure emerges, where elevated bifurcation remains between 475 and 600 K, and a mostly single-walled barrier occurs at other levels. While bifurcation at a given level evolves from month to month, and does not always persist through a season, interannual variations in the strength of bifurcation display coherence across multiple levels in any given month. Accounting for bifurcation allows the region of reduced mixing to be better characterised. These results suggest that improved understanding of cross-vortex mixing requires consideration of the polar vortex not as a single mixing barrier but as a barrier with internal structure that is likely to manifest as more complex gradients in trace gas concentrations across the vortex barrier region. |
format |
Text |
author |
Conway, Jonathan Bodeker, Greg Cameron, Chris |
spellingShingle |
Conway, Jonathan Bodeker, Greg Cameron, Chris Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex |
author_facet |
Conway, Jonathan Bodeker, Greg Cameron, Chris |
author_sort |
Conway, Jonathan |
title |
Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex |
title_short |
Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex |
title_full |
Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex |
title_fullStr |
Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex |
title_full_unstemmed |
Bifurcation of potential vorticity gradients across the Southern Hemisphere stratospheric polar vortex |
title_sort |
bifurcation of potential vorticity gradients across the southern hemisphere stratospheric polar vortex |
publishDate |
2019 |
url |
https://doi.org/10.5194/acp-18-8065-2018 https://www.atmos-chem-phys.net/18/8065/2018/ |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-18-8065-2018 https://www.atmos-chem-phys.net/18/8065/2018/ |
op_doi |
https://doi.org/10.5194/acp-18-8065-2018 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
18 |
container_issue |
11 |
container_start_page |
8065 |
op_container_end_page |
8077 |
_version_ |
1766060983749443584 |