A new perspective on blocking
It is argued that the essential aspect of atmospheric blocking may be seen in the wave breaking of potential temperature (θ) on a potential vorticity (PV) surface, which may be identified with the tropopause, and the consequent reversal of the usual meridional temperature gradient of θ. A new dynami...
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ftunivreading:oai:centaur.reading.ac.uk:5285 2024-09-15T18:23:02+00:00 A new perspective on blocking Pelly, J.L. Hoskins, B.J. 2003 https://centaur.reading.ac.uk/5285/ unknown American Meteorological Society Pelly, J.L. and Hoskins, B.J. <https://centaur.reading.ac.uk/view/creators/90000043.html> (2003) A new perspective on blocking. Journal of the Atmospheric Sciences, 60. pp. 743-755. ISSN 1520-0469 doi: https://doi.org/10.1175/1520-0469(2003)060<0743:ANPOB>2.0.CO;2 <https://doi.org/10.1175/1520-0469(2003)060<0743:ANPOB>2.0.CO;2> 551 Geology hydrology meteorology Article PeerReviewed 2003 ftunivreading https://doi.org/10.1175/1520-0469(2003)060<0743:ANPOB>2.0.CO;2 2024-08-12T23:43:15Z It is argued that the essential aspect of atmospheric blocking may be seen in the wave breaking of potential temperature (θ) on a potential vorticity (PV) surface, which may be identified with the tropopause, and the consequent reversal of the usual meridional temperature gradient of θ. A new dynamical blocking index is constructed using a meridional θ difference on a PV surface. Unlike in previous studies, the central blocking latitude about which this difference is constructed is allowed to vary with longitude. At each longitude it is determined by the latitude at which the climatological high-pass transient eddy kinetic energy is a maximum. Based on the blocking index, at each longitude local instantaneous blocking, large-scale blocking, and blocking episodes are defined. For longitudinal sectors, sector blocking and sector blocking episodes are also defined. The 5-yr annual climatologies of the three longitudinally defined blocking event frequencies and the seasonal climatologies of blocking episode frequency are shown. The climatologies all pick out the eastern North Atlantic–Europe and eastern North Pacific–western North America regions. There is evidence that Pacific blocking shifts into the western central Pacific in the summer. Sector blocking episodes of 4 days or more are shown to exhibit different persistence characteristics to shorter events, showing that blocking is not just the long timescale tail end of a distribution. The PV–θ index results for the annual average location of Pacific blocking agree with synoptic studies but disagree with modern quantitative height field–based studies. It is considered that the index used here is to be preferred anyway because of its dynamical basis. However, the longitudinal discrepancy is found to be associated with the use in the height field index studies of a central blocking latitude that is independent of longitude. In particular, the use in the North Pacific of a latitude that is suitable for the eastern North Atlantic leads to spurious categorization of ... Article in Journal/Newspaper North Atlantic CentAUR: Central Archive at the University of Reading |
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Open Polar |
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CentAUR: Central Archive at the University of Reading |
op_collection_id |
ftunivreading |
language |
unknown |
topic |
551 Geology hydrology meteorology |
spellingShingle |
551 Geology hydrology meteorology Pelly, J.L. Hoskins, B.J. A new perspective on blocking |
topic_facet |
551 Geology hydrology meteorology |
description |
It is argued that the essential aspect of atmospheric blocking may be seen in the wave breaking of potential temperature (θ) on a potential vorticity (PV) surface, which may be identified with the tropopause, and the consequent reversal of the usual meridional temperature gradient of θ. A new dynamical blocking index is constructed using a meridional θ difference on a PV surface. Unlike in previous studies, the central blocking latitude about which this difference is constructed is allowed to vary with longitude. At each longitude it is determined by the latitude at which the climatological high-pass transient eddy kinetic energy is a maximum. Based on the blocking index, at each longitude local instantaneous blocking, large-scale blocking, and blocking episodes are defined. For longitudinal sectors, sector blocking and sector blocking episodes are also defined. The 5-yr annual climatologies of the three longitudinally defined blocking event frequencies and the seasonal climatologies of blocking episode frequency are shown. The climatologies all pick out the eastern North Atlantic–Europe and eastern North Pacific–western North America regions. There is evidence that Pacific blocking shifts into the western central Pacific in the summer. Sector blocking episodes of 4 days or more are shown to exhibit different persistence characteristics to shorter events, showing that blocking is not just the long timescale tail end of a distribution. The PV–θ index results for the annual average location of Pacific blocking agree with synoptic studies but disagree with modern quantitative height field–based studies. It is considered that the index used here is to be preferred anyway because of its dynamical basis. However, the longitudinal discrepancy is found to be associated with the use in the height field index studies of a central blocking latitude that is independent of longitude. In particular, the use in the North Pacific of a latitude that is suitable for the eastern North Atlantic leads to spurious categorization of ... |
format |
Article in Journal/Newspaper |
author |
Pelly, J.L. Hoskins, B.J. |
author_facet |
Pelly, J.L. Hoskins, B.J. |
author_sort |
Pelly, J.L. |
title |
A new perspective on blocking |
title_short |
A new perspective on blocking |
title_full |
A new perspective on blocking |
title_fullStr |
A new perspective on blocking |
title_full_unstemmed |
A new perspective on blocking |
title_sort |
new perspective on blocking |
publisher |
American Meteorological Society |
publishDate |
2003 |
url |
https://centaur.reading.ac.uk/5285/ |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
Pelly, J.L. and Hoskins, B.J. <https://centaur.reading.ac.uk/view/creators/90000043.html> (2003) A new perspective on blocking. Journal of the Atmospheric Sciences, 60. pp. 743-755. ISSN 1520-0469 doi: https://doi.org/10.1175/1520-0469(2003)060<0743:ANPOB>2.0.CO;2 <https://doi.org/10.1175/1520-0469(2003)060<0743:ANPOB>2.0.CO;2> |
op_doi |
https://doi.org/10.1175/1520-0469(2003)060<0743:ANPOB>2.0.CO;2 |
_version_ |
1810463148094783488 |