Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions
Both the positive and negative phases of the North Atlantic Oscillation (NAO⁺ and NAO⁻, respectively) and atmospheric blocking in the Euro-Atlantic sector reflect synoptic variability over the region and thus are intrinsically linked. This study examines their relationship from a decadal change pers...
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American Meteorological Society
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ftncar:oai:drupal-site.org:articles_16549 2023-09-05T13:21:28+02:00 Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions Luo, Dehai (author) Yao, Yao (author) Dai, Aiguo (author) 2015-03-01 application/pdf http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-583 https://doi.org/10.1175/JAS-D-14-0039.1 en eng American Meteorological Society Journal of the Atmospheric Sciences http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-583 doi:10.1175/JAS-D-14-0039.1 ark:/85065/d78k7b7d Copyright 2015 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work. Text article 2015 ftncar https://doi.org/10.1175/JAS-D-14-0039.1 2023-08-14T18:43:57Z Both the positive and negative phases of the North Atlantic Oscillation (NAO⁺ and NAO⁻, respectively) and atmospheric blocking in the Euro-Atlantic sector reflect synoptic variability over the region and thus are intrinsically linked. This study examines their relationship from a decadal change perspective. Since the winter-mean NAO index is defined as a time average of instantaneous NAO indices over the whole winter, it is unclear how the activity of European blocking (EB) events can be related to the variation of the positive mean NAO index. Here, this question is examined by dividing the winter period 1978-2011 into two decadal epochs: 1978-94 (P1) with an increasing and high NAO index and 1995-2011 (P2) with a decreasing and low NAO index. Using atmospheric reanalysis data, it is shown that there are more intense and persistent EB events in eastern Europe during P1 than during P2, while the opposite is true for western Europe. It is further shown that there are more NAO⁺ (NAO⁻) events during P1 (P2). The EB events associated with NAO⁺ events extend more eastward and are associated with stronger Atlantic mean zonal wind and weaker western Atlantic storm track during P1 than during P2, but EB events associated with NAO⁻ events increase in western Europe under opposite Atlantic conditions during P2. Thus, the increase in the number of individual NAO⁺ (NAO⁻) events results in more EB events in eastern (western) Europe during P1 (P2). The EB change is also associated with the increased frequency of NAO⁻ to NAO⁺ (NAO⁺ to NAO⁻) transition events. Article in Journal/Newspaper North Atlantic North Atlantic oscillation OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) Journal of the Atmospheric Sciences 72 3 1152 1173 |
institution |
Open Polar |
collection |
OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) |
op_collection_id |
ftncar |
language |
English |
description |
Both the positive and negative phases of the North Atlantic Oscillation (NAO⁺ and NAO⁻, respectively) and atmospheric blocking in the Euro-Atlantic sector reflect synoptic variability over the region and thus are intrinsically linked. This study examines their relationship from a decadal change perspective. Since the winter-mean NAO index is defined as a time average of instantaneous NAO indices over the whole winter, it is unclear how the activity of European blocking (EB) events can be related to the variation of the positive mean NAO index. Here, this question is examined by dividing the winter period 1978-2011 into two decadal epochs: 1978-94 (P1) with an increasing and high NAO index and 1995-2011 (P2) with a decreasing and low NAO index. Using atmospheric reanalysis data, it is shown that there are more intense and persistent EB events in eastern Europe during P1 than during P2, while the opposite is true for western Europe. It is further shown that there are more NAO⁺ (NAO⁻) events during P1 (P2). The EB events associated with NAO⁺ events extend more eastward and are associated with stronger Atlantic mean zonal wind and weaker western Atlantic storm track during P1 than during P2, but EB events associated with NAO⁻ events increase in western Europe under opposite Atlantic conditions during P2. Thus, the increase in the number of individual NAO⁺ (NAO⁻) events results in more EB events in eastern (western) Europe during P1 (P2). The EB change is also associated with the increased frequency of NAO⁻ to NAO⁺ (NAO⁺ to NAO⁻) transition events. |
author2 |
Luo, Dehai (author) Yao, Yao (author) Dai, Aiguo (author) |
format |
Article in Journal/Newspaper |
title |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions |
spellingShingle |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions |
title_short |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions |
title_full |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions |
title_fullStr |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions |
title_full_unstemmed |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part I: Atlantic conditions |
title_sort |
decadal relationship between european blocking and the north atlantic oscillation during 1978-2011. part i: atlantic conditions |
publisher |
American Meteorological Society |
publishDate |
2015 |
url |
http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-583 https://doi.org/10.1175/JAS-D-14-0039.1 |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_relation |
Journal of the Atmospheric Sciences http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-583 doi:10.1175/JAS-D-14-0039.1 ark:/85065/d78k7b7d |
op_rights |
Copyright 2015 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work. |
op_doi |
https://doi.org/10.1175/JAS-D-14-0039.1 |
container_title |
Journal of the Atmospheric Sciences |
container_volume |
72 |
container_issue |
3 |
container_start_page |
1152 |
op_container_end_page |
1173 |
_version_ |
1776202070097920000 |