Evidence for nonlinearity in observed stratospheric circulation changes
The leading mode of variability of the lower atmosphere circulation in the Northern Hemisphere is a largely zonally symmetric mode known as the Arctic Oscillation. We calculate Arctic Oscillation (AO) indices on a range of levels from 1000 to 10 hPa by means of a principal component analysis of Nati...
Published in: | Journal of Geophysical Research: Atmospheres |
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Format: | Article in Journal/Newspaper |
Language: | English |
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Blackwell Publishing Ltd
2016
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Online Access: | https://doi.org/10.1029/2000JD900720 https://ora.ox.ac.uk/objects/uuid:d65203c3-45cd-4e10-b220-d1d947895cdc |
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ftuloxford:oai:ora.ox.ac.uk:uuid:d65203c3-45cd-4e10-b220-d1d947895cdc 2023-05-15T14:59:16+02:00 Evidence for nonlinearity in observed stratospheric circulation changes Gillett, N Baldwin, M Allen, M 2016-07-29 https://doi.org/10.1029/2000JD900720 https://ora.ox.ac.uk/objects/uuid:d65203c3-45cd-4e10-b220-d1d947895cdc eng eng Blackwell Publishing Ltd doi:10.1029/2000JD900720 https://ora.ox.ac.uk/objects/uuid:d65203c3-45cd-4e10-b220-d1d947895cdc https://doi.org/10.1029/2000JD900720 info:eu-repo/semantics/embargoedAccess Journal article 2016 ftuloxford https://doi.org/10.1029/2000JD900720 2022-06-28T20:25:04Z The leading mode of variability of the lower atmosphere circulation in the Northern Hemisphere is a largely zonally symmetric mode known as the Arctic Oscillation. We calculate Arctic Oscillation (AO) indices on a range of levels from 1000 to 10 hPa by means of a principal component analysis of National Centers for Environmental Prediction daily geopotential height anomalies. We find the apparent downward propagation of anomalies noted by other authors to be statistically significant compared to a red noise model. By examining histograms of these indices for each month, we note that the distribution of the index is generally close to Gaussian in the troposphere. In the stratosphere, however, the index is negatively skewed in the winter and positively skewed in the spring. We conclude that the positive skewness in April results from the coexistence of distinct summer and winter circulation states, and by examining polar stratospheric temperatures, we conclude that the negative skewness in January may be due to the radiatively determined limit on the vortex strength. This radiative limit responds relatively slowly to anthropogenic forcing, whereas changes in planetary wave forcing could have a much faster impact on the number of warm events. This suggests a hypothesis that the vortex strength may respond nonlinearly to anthropogenic forcing, which is supported by an observed change in the shape of the histograms of 20-200 hPa AO indices in January over the past 40 years. Copyright 2001 by the American Geophysical Union. Article in Journal/Newspaper Arctic ORA - Oxford University Research Archive Arctic Journal of Geophysical Research: Atmospheres 106 D8 7891 7901 |
institution |
Open Polar |
collection |
ORA - Oxford University Research Archive |
op_collection_id |
ftuloxford |
language |
English |
description |
The leading mode of variability of the lower atmosphere circulation in the Northern Hemisphere is a largely zonally symmetric mode known as the Arctic Oscillation. We calculate Arctic Oscillation (AO) indices on a range of levels from 1000 to 10 hPa by means of a principal component analysis of National Centers for Environmental Prediction daily geopotential height anomalies. We find the apparent downward propagation of anomalies noted by other authors to be statistically significant compared to a red noise model. By examining histograms of these indices for each month, we note that the distribution of the index is generally close to Gaussian in the troposphere. In the stratosphere, however, the index is negatively skewed in the winter and positively skewed in the spring. We conclude that the positive skewness in April results from the coexistence of distinct summer and winter circulation states, and by examining polar stratospheric temperatures, we conclude that the negative skewness in January may be due to the radiatively determined limit on the vortex strength. This radiative limit responds relatively slowly to anthropogenic forcing, whereas changes in planetary wave forcing could have a much faster impact on the number of warm events. This suggests a hypothesis that the vortex strength may respond nonlinearly to anthropogenic forcing, which is supported by an observed change in the shape of the histograms of 20-200 hPa AO indices in January over the past 40 years. Copyright 2001 by the American Geophysical Union. |
format |
Article in Journal/Newspaper |
author |
Gillett, N Baldwin, M Allen, M |
spellingShingle |
Gillett, N Baldwin, M Allen, M Evidence for nonlinearity in observed stratospheric circulation changes |
author_facet |
Gillett, N Baldwin, M Allen, M |
author_sort |
Gillett, N |
title |
Evidence for nonlinearity in observed stratospheric circulation changes |
title_short |
Evidence for nonlinearity in observed stratospheric circulation changes |
title_full |
Evidence for nonlinearity in observed stratospheric circulation changes |
title_fullStr |
Evidence for nonlinearity in observed stratospheric circulation changes |
title_full_unstemmed |
Evidence for nonlinearity in observed stratospheric circulation changes |
title_sort |
evidence for nonlinearity in observed stratospheric circulation changes |
publisher |
Blackwell Publishing Ltd |
publishDate |
2016 |
url |
https://doi.org/10.1029/2000JD900720 https://ora.ox.ac.uk/objects/uuid:d65203c3-45cd-4e10-b220-d1d947895cdc |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_relation |
doi:10.1029/2000JD900720 https://ora.ox.ac.uk/objects/uuid:d65203c3-45cd-4e10-b220-d1d947895cdc https://doi.org/10.1029/2000JD900720 |
op_rights |
info:eu-repo/semantics/embargoedAccess |
op_doi |
https://doi.org/10.1029/2000JD900720 |
container_title |
Journal of Geophysical Research: Atmospheres |
container_volume |
106 |
container_issue |
D8 |
container_start_page |
7891 |
op_container_end_page |
7901 |
_version_ |
1766331384922636288 |