Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study
In Part I of this study, it is revealed that decadal variations of European blocking, in its intensity, duration, and position, during 1978-2011 are modulated by decadal changes in the frequency of North Atlantic Oscillation (NAO) events associated with background Atlantic conditions. In Part II, re...
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ftncar:oai:drupal-site.org:articles_16548 2023-09-05T13:21:29+02:00 Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study Luo, Dehai (author) Yao, Yao (author) Dai, Aiguo (author) 2015-03-01 application/pdf http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-582 https://doi.org/10.1175/JAS-D-14-0040.1 en eng American Meteorological Society Journal of the Atmospheric Sciences http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-582 doi:10.1175/JAS-D-14-0040.1 ark:/85065/d7db8311 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-14-0040.1 2023-08-14T18:43:57Z In Part I of this study, it is revealed that decadal variations of European blocking, in its intensity, duration, and position, during 1978-2011 are modulated by decadal changes in the frequency of North Atlantic Oscillation (NAO) events associated with background Atlantic conditions. In Part II, reanalysis data are analyzed to first show that a T-bone-type structure of the climatological-mean blocking frequency in the Euro-Atlantic sector roughly results from a combination of the blocking frequency distributions along the southeast-northwest (SE-NW) direction associated with negative-phase NAO (NAO⁻) events and along the southwest–northeast (SW-NE) direction associated with positive-phase NAO (NAO⁺) events. A nonlinear multiscale interaction (NMI) model is then used to examine the physical processes behind the blocking frequency distributions. This model shows that the combination of eastward- and westward-displaced blocking frequency patterns along the SW-NE and SE-NW directions associated with NAO⁺ and NAO⁻ events leads to a T-bone-type frequency distribution, as seen in reanalysis data. Moreover, it is found that the westward migration of intense, long-lived blocking anomalies over Europe following NAO⁺ events is favored (suppressed) when the Atlantic mean zonal wind is relatively weak (strong). This result is held for the strong (weak) western Atlantic storm track. This helps explain the findings in Part I. In particular, long-lived blocking events with double peaks can form over Europe because of reintensification during the NAO⁺ decay phase, when the mean zonal wind weakens. But the double-peak structure disappears and becomes a strong single-peak structure as the mean zonal wind strengthens. 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 1174 1199 |
institution |
Open Polar |
collection |
OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) |
op_collection_id |
ftncar |
language |
English |
description |
In Part I of this study, it is revealed that decadal variations of European blocking, in its intensity, duration, and position, during 1978-2011 are modulated by decadal changes in the frequency of North Atlantic Oscillation (NAO) events associated with background Atlantic conditions. In Part II, reanalysis data are analyzed to first show that a T-bone-type structure of the climatological-mean blocking frequency in the Euro-Atlantic sector roughly results from a combination of the blocking frequency distributions along the southeast-northwest (SE-NW) direction associated with negative-phase NAO (NAO⁻) events and along the southwest–northeast (SW-NE) direction associated with positive-phase NAO (NAO⁺) events. A nonlinear multiscale interaction (NMI) model is then used to examine the physical processes behind the blocking frequency distributions. This model shows that the combination of eastward- and westward-displaced blocking frequency patterns along the SW-NE and SE-NW directions associated with NAO⁺ and NAO⁻ events leads to a T-bone-type frequency distribution, as seen in reanalysis data. Moreover, it is found that the westward migration of intense, long-lived blocking anomalies over Europe following NAO⁺ events is favored (suppressed) when the Atlantic mean zonal wind is relatively weak (strong). This result is held for the strong (weak) western Atlantic storm track. This helps explain the findings in Part I. In particular, long-lived blocking events with double peaks can form over Europe because of reintensification during the NAO⁺ decay phase, when the mean zonal wind weakens. But the double-peak structure disappears and becomes a strong single-peak structure as the mean zonal wind strengthens. |
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 II: A theoretical model study |
spellingShingle |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study |
title_short |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study |
title_full |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study |
title_fullStr |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study |
title_full_unstemmed |
Decadal relationship between European blocking and the North Atlantic Oscillation during 1978-2011. Part II: A theoretical model study |
title_sort |
decadal relationship between european blocking and the north atlantic oscillation during 1978-2011. part ii: a theoretical model study |
publisher |
American Meteorological Society |
publishDate |
2015 |
url |
http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-021-582 https://doi.org/10.1175/JAS-D-14-0040.1 |
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-000-000-021-582 doi:10.1175/JAS-D-14-0040.1 ark:/85065/d7db8311 |
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-14-0040.1 |
container_title |
Journal of the Atmospheric Sciences |
container_volume |
72 |
container_issue |
3 |
container_start_page |
1174 |
op_container_end_page |
1199 |
_version_ |
1776202082582265856 |