Characterisation of the Antarctic stratospheric vortex mixing barrier
The strongest stratospheric circulation in the Southern Hemisphere is the Antarctic Circumpolar Vortex (ACV) which forms each winter and spring as a zone of westerly winds surrounding Antarctica, presenting a barrier to transport of air masses between middle and high-latitudes. This barrier contribu...
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ftvictoriauwfig:oai:figshare.com:article/17142071 2023-05-15T13:35:14+02:00 Characterisation of the Antarctic stratospheric vortex mixing barrier Cameron, Christopher 2019-01-01T00:00:00Z https://doi.org/10.26686/wgtn.17142071.v1 https://figshare.com/articles/thesis/Characterisation_of_the_Antarctic_stratospheric_vortex_mixing_barrier/17142071 unknown doi:10.26686/wgtn.17142071.v1 https://figshare.com/articles/thesis/Characterisation_of_the_Antarctic_stratospheric_vortex_mixing_barrier/17142071 Author Retains Copyright Atmospheric Dynamics Geodynamics Climate Vortex Stratosphere School: School of Geography Environment and Earth Sciences 040102 Atmospheric Dynamics 040402 Geodynamics 960303 Climate Change Models 960202 Atmospheric Processes and Dynamics Degree Discipline: Geophysics Degree Level: Doctoral Degree Name: Doctor of Philosophy Text Thesis 2019 ftvictoriauwfig https://doi.org/10.26686/wgtn.17142071.v1 2021-12-09T00:04:34Z The strongest stratospheric circulation in the Southern Hemisphere is the Antarctic Circumpolar Vortex (ACV) which forms each winter and spring as a zone of westerly winds surrounding Antarctica, presenting a barrier to transport of air masses between middle and high-latitudes. This barrier contributes to stratospheric temperatures above the polar region dropping sufficiently low in spring to allow for the processes leading to ozone destruction. Unfortunately, the ACV is generally not well simulated in Global Climate Models (GCMs), and this presents a challenge for model accuracy and projections in the face of a changing climate and a recovering ozone hole. In this research, an assessment is made of the performance of a range of mixing metrics in representing the ACV based on reanalyses, including: Effective Diffusivity, Contour Crossing, the Lagrangian function $M$, and Meridional Impermeability. It is shown that Meridional Impermeability -- which provides a measure of the strength of the meridional mixing barrier as a function of potential vorticity (PV) gradient and wind-speed -- acts as a useful proxy for more complex metrics. In addition, Meridional Impermeability displays a well-defined vortex profile across equivalent latitude, which is not seen to the same degree in the other metrics assessed. Representation of the ACV is further compared between climate models and reanalyses based on Meridional Impermeability. It is shown that while climate models have improved in their representation of the vortex barrier over time, there are still significant discrepancies between models and reanalyses. One cause of these discrepancies may result from the use of prescribed ozone fields rather than interactive ozone chemistry. This is further examined by comparing Chemistry Climate Model (CCM) simulations using interactive ozone chemistry, with those using prescribed ozone at either 3-D (i.e., height, latitude and longitude) or 2-D (i.e., height, latitude) dimensionality. Considerable improvement in the representation ... Thesis Antarc* Antarctic Antarctica Open Access Victoria University of Wellington / Te Herenga Waka Antarctic The Antarctic |
institution |
Open Polar |
collection |
Open Access Victoria University of Wellington / Te Herenga Waka |
op_collection_id |
ftvictoriauwfig |
language |
unknown |
topic |
Atmospheric Dynamics Geodynamics Climate Vortex Stratosphere School: School of Geography Environment and Earth Sciences 040102 Atmospheric Dynamics 040402 Geodynamics 960303 Climate Change Models 960202 Atmospheric Processes and Dynamics Degree Discipline: Geophysics Degree Level: Doctoral Degree Name: Doctor of Philosophy |
spellingShingle |
Atmospheric Dynamics Geodynamics Climate Vortex Stratosphere School: School of Geography Environment and Earth Sciences 040102 Atmospheric Dynamics 040402 Geodynamics 960303 Climate Change Models 960202 Atmospheric Processes and Dynamics Degree Discipline: Geophysics Degree Level: Doctoral Degree Name: Doctor of Philosophy Cameron, Christopher Characterisation of the Antarctic stratospheric vortex mixing barrier |
topic_facet |
Atmospheric Dynamics Geodynamics Climate Vortex Stratosphere School: School of Geography Environment and Earth Sciences 040102 Atmospheric Dynamics 040402 Geodynamics 960303 Climate Change Models 960202 Atmospheric Processes and Dynamics Degree Discipline: Geophysics Degree Level: Doctoral Degree Name: Doctor of Philosophy |
description |
The strongest stratospheric circulation in the Southern Hemisphere is the Antarctic Circumpolar Vortex (ACV) which forms each winter and spring as a zone of westerly winds surrounding Antarctica, presenting a barrier to transport of air masses between middle and high-latitudes. This barrier contributes to stratospheric temperatures above the polar region dropping sufficiently low in spring to allow for the processes leading to ozone destruction. Unfortunately, the ACV is generally not well simulated in Global Climate Models (GCMs), and this presents a challenge for model accuracy and projections in the face of a changing climate and a recovering ozone hole. In this research, an assessment is made of the performance of a range of mixing metrics in representing the ACV based on reanalyses, including: Effective Diffusivity, Contour Crossing, the Lagrangian function $M$, and Meridional Impermeability. It is shown that Meridional Impermeability -- which provides a measure of the strength of the meridional mixing barrier as a function of potential vorticity (PV) gradient and wind-speed -- acts as a useful proxy for more complex metrics. In addition, Meridional Impermeability displays a well-defined vortex profile across equivalent latitude, which is not seen to the same degree in the other metrics assessed. Representation of the ACV is further compared between climate models and reanalyses based on Meridional Impermeability. It is shown that while climate models have improved in their representation of the vortex barrier over time, there are still significant discrepancies between models and reanalyses. One cause of these discrepancies may result from the use of prescribed ozone fields rather than interactive ozone chemistry. This is further examined by comparing Chemistry Climate Model (CCM) simulations using interactive ozone chemistry, with those using prescribed ozone at either 3-D (i.e., height, latitude and longitude) or 2-D (i.e., height, latitude) dimensionality. Considerable improvement in the representation ... |
format |
Thesis |
author |
Cameron, Christopher |
author_facet |
Cameron, Christopher |
author_sort |
Cameron, Christopher |
title |
Characterisation of the Antarctic stratospheric vortex mixing barrier |
title_short |
Characterisation of the Antarctic stratospheric vortex mixing barrier |
title_full |
Characterisation of the Antarctic stratospheric vortex mixing barrier |
title_fullStr |
Characterisation of the Antarctic stratospheric vortex mixing barrier |
title_full_unstemmed |
Characterisation of the Antarctic stratospheric vortex mixing barrier |
title_sort |
characterisation of the antarctic stratospheric vortex mixing barrier |
publishDate |
2019 |
url |
https://doi.org/10.26686/wgtn.17142071.v1 https://figshare.com/articles/thesis/Characterisation_of_the_Antarctic_stratospheric_vortex_mixing_barrier/17142071 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_relation |
doi:10.26686/wgtn.17142071.v1 https://figshare.com/articles/thesis/Characterisation_of_the_Antarctic_stratospheric_vortex_mixing_barrier/17142071 |
op_rights |
Author Retains Copyright |
op_doi |
https://doi.org/10.26686/wgtn.17142071.v1 |
_version_ |
1766063347269107712 |