Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector
Atmospheric circulation is often clustered in so‐called circulation regimes, which are persistent and recurrent patterns. For the Euro‐Atlantic sector in winter, most studies identify four regimes: the Atlantic Ridge, Scandinavian Blocking and the two phases of the North Atlantic Oscillation. These...
Published in: | Quarterly Journal of the Royal Meteorological Society |
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ftuloxford:oai:ora.ox.ac.uk:uuid:56267646-a077-47a9-a4ef-d2ad40978f7e 2023-05-15T17:34:10+02:00 Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector Falkena, SKJ de Wiljes, J Weisheimer, A Shepherd, TG 2020-05-14 https://doi.org/10.1002/qj.3818 https://ora.ox.ac.uk/objects/uuid:56267646-a077-47a9-a4ef-d2ad40978f7e eng eng Wiley doi:10.1002/qj.3818 https://ora.ox.ac.uk/objects/uuid:56267646-a077-47a9-a4ef-d2ad40978f7e https://doi.org/10.1002/qj.3818 info:eu-repo/semantics/openAccess CC Attribution (CC BY) CC-BY Journal article 2020 ftuloxford https://doi.org/10.1002/qj.3818 2022-06-28T20:12:39Z Atmospheric circulation is often clustered in so‐called circulation regimes, which are persistent and recurrent patterns. For the Euro‐Atlantic sector in winter, most studies identify four regimes: the Atlantic Ridge, Scandinavian Blocking and the two phases of the North Atlantic Oscillation. These results are obtained by applying k‐means clustering to the first several empirical orthogonal functions (EOFs) of geopotential height data. Studying the observed circulation in reanalysis data, it is found that when the full field data are used for the k‐means cluster analysis instead of the EOFs, the optimal number of clusters is no longer four but six. The two extra regimes that are found are the opposites of the Atlantic Ridge and Scandinavian Blocking, meaning they have a low‐pressure area roughly where the original regimes have a high‐pressure area. This introduces an appealing symmetry in the clustering result. Incorporating a weak persistence constraint in the clustering procedure is found to lead to a longer duration of regimes, extending beyond the synoptic time‐scale, without changing their occurrence rates. This is in contrast to the commonly used application of a time‐filter to the data before the clustering is executed, which, while increasing the persistence, changes the occurrence rates of the regimes. We conclude that applying a persistence constraint within the clustering procedure is a better way of stabilizing the clustering results than low‐pass filtering the data. Article in Journal/Newspaper North Atlantic North Atlantic oscillation ORA - Oxford University Research Archive Quarterly Journal of the Royal Meteorological Society 146 731 2801 2814 |
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Open Polar |
collection |
ORA - Oxford University Research Archive |
op_collection_id |
ftuloxford |
language |
English |
description |
Atmospheric circulation is often clustered in so‐called circulation regimes, which are persistent and recurrent patterns. For the Euro‐Atlantic sector in winter, most studies identify four regimes: the Atlantic Ridge, Scandinavian Blocking and the two phases of the North Atlantic Oscillation. These results are obtained by applying k‐means clustering to the first several empirical orthogonal functions (EOFs) of geopotential height data. Studying the observed circulation in reanalysis data, it is found that when the full field data are used for the k‐means cluster analysis instead of the EOFs, the optimal number of clusters is no longer four but six. The two extra regimes that are found are the opposites of the Atlantic Ridge and Scandinavian Blocking, meaning they have a low‐pressure area roughly where the original regimes have a high‐pressure area. This introduces an appealing symmetry in the clustering result. Incorporating a weak persistence constraint in the clustering procedure is found to lead to a longer duration of regimes, extending beyond the synoptic time‐scale, without changing their occurrence rates. This is in contrast to the commonly used application of a time‐filter to the data before the clustering is executed, which, while increasing the persistence, changes the occurrence rates of the regimes. We conclude that applying a persistence constraint within the clustering procedure is a better way of stabilizing the clustering results than low‐pass filtering the data. |
format |
Article in Journal/Newspaper |
author |
Falkena, SKJ de Wiljes, J Weisheimer, A Shepherd, TG |
spellingShingle |
Falkena, SKJ de Wiljes, J Weisheimer, A Shepherd, TG Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector |
author_facet |
Falkena, SKJ de Wiljes, J Weisheimer, A Shepherd, TG |
author_sort |
Falkena, SKJ |
title |
Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector |
title_short |
Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector |
title_full |
Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector |
title_fullStr |
Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector |
title_full_unstemmed |
Revisiting the identification of wintertime atmospheric circulation regimes in the Euro‐Atlantic sector |
title_sort |
revisiting the identification of wintertime atmospheric circulation regimes in the euro‐atlantic sector |
publisher |
Wiley |
publishDate |
2020 |
url |
https://doi.org/10.1002/qj.3818 https://ora.ox.ac.uk/objects/uuid:56267646-a077-47a9-a4ef-d2ad40978f7e |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_relation |
doi:10.1002/qj.3818 https://ora.ox.ac.uk/objects/uuid:56267646-a077-47a9-a4ef-d2ad40978f7e https://doi.org/10.1002/qj.3818 |
op_rights |
info:eu-repo/semantics/openAccess CC Attribution (CC BY) |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1002/qj.3818 |
container_title |
Quarterly Journal of the Royal Meteorological Society |
container_volume |
146 |
container_issue |
731 |
container_start_page |
2801 |
op_container_end_page |
2814 |
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1766132918579625984 |