Tropospheric Rossby wave breaking and the NAO/NAM
Objective analysis of several hundred thousand anticyclonic and cyclonic breaking Rossby waves is performed for the Northern Hemisphere (NH) winters of 1958-2006. A winter climatology of both anti-cyclonic and cyclonic Rossby wave breaking (RWB) frequency and size (zonal extent) is presented for the...
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ftcdlib:oai:escholarship.org/ark:/13030/qt66v6z326 2023-05-15T17:35:13+02:00 Tropospheric Rossby wave breaking and the NAO/NAM Strong, C Magnusdottir, G 2861 - 2876 2008-12-04 application/pdf https://escholarship.org/uc/item/66v6z326 unknown eScholarship, University of California qt66v6z326 https://escholarship.org/uc/item/66v6z326 CC-BY CC-BY Journal of the Atmospheric Sciences, vol 65, iss 9 Meteorology & Atmospheric Sciences Atmospheric Sciences article 2008 ftcdlib 2020-03-20T23:55:58Z Objective analysis of several hundred thousand anticyclonic and cyclonic breaking Rossby waves is performed for the Northern Hemisphere (NH) winters of 1958-2006. A winter climatology of both anti-cyclonic and cyclonic Rossby wave breaking (RWB) frequency and size (zonal extent) is presented for the 350-K isentropic surface over the NH, and the spatial distribution of RWB is shown to agree with theoretical ideas of RWB in shear flow. Composites of the two types of RWB reveal their characteristic sea level pressure anomalies, upper- and lower-tropospheric velocity fields, and forcing of the upper-tropospheric zonal flow. It is shown how these signatures project onto the centers of action and force the velocity patterns associated with the North Atlantic Oscillation (NAO) and Northern Hemisphere annular mode (NAM). Previous studies have presented evidence that anticyclonic (cyclonic) breaking leads to the positive (negative) polarity of the NAO, and this relationship is confirmed for RWB over the midlatitudes centered near 50°N. However, an opposite and statistically significant relationship, in which cyclonic RWB forces the positive NAO and anticyclonic RWB forces the negative NAO, is shown over regions 20° to the north and south, centered at 70° and 30°N, respectively. On a winter mean basis, the frequency of RWB over objectively defined regions covering 12% of the area of the NH accounts for 95% of the NAO index and 92% of the NAM index. A 6-hourly analysis of all the winters indicates that RWB over the objectively defined regions affects the NAO/ NAM without a time lag. Details of the objective wave-breaking analysis method are provided in the appendix. © 2008 American Meteorological Society. Article in Journal/Newspaper North Atlantic North Atlantic oscillation University of California: eScholarship |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Meteorology & Atmospheric Sciences Atmospheric Sciences |
spellingShingle |
Meteorology & Atmospheric Sciences Atmospheric Sciences Strong, C Magnusdottir, G Tropospheric Rossby wave breaking and the NAO/NAM |
topic_facet |
Meteorology & Atmospheric Sciences Atmospheric Sciences |
description |
Objective analysis of several hundred thousand anticyclonic and cyclonic breaking Rossby waves is performed for the Northern Hemisphere (NH) winters of 1958-2006. A winter climatology of both anti-cyclonic and cyclonic Rossby wave breaking (RWB) frequency and size (zonal extent) is presented for the 350-K isentropic surface over the NH, and the spatial distribution of RWB is shown to agree with theoretical ideas of RWB in shear flow. Composites of the two types of RWB reveal their characteristic sea level pressure anomalies, upper- and lower-tropospheric velocity fields, and forcing of the upper-tropospheric zonal flow. It is shown how these signatures project onto the centers of action and force the velocity patterns associated with the North Atlantic Oscillation (NAO) and Northern Hemisphere annular mode (NAM). Previous studies have presented evidence that anticyclonic (cyclonic) breaking leads to the positive (negative) polarity of the NAO, and this relationship is confirmed for RWB over the midlatitudes centered near 50°N. However, an opposite and statistically significant relationship, in which cyclonic RWB forces the positive NAO and anticyclonic RWB forces the negative NAO, is shown over regions 20° to the north and south, centered at 70° and 30°N, respectively. On a winter mean basis, the frequency of RWB over objectively defined regions covering 12% of the area of the NH accounts for 95% of the NAO index and 92% of the NAM index. A 6-hourly analysis of all the winters indicates that RWB over the objectively defined regions affects the NAO/ NAM without a time lag. Details of the objective wave-breaking analysis method are provided in the appendix. © 2008 American Meteorological Society. |
format |
Article in Journal/Newspaper |
author |
Strong, C Magnusdottir, G |
author_facet |
Strong, C Magnusdottir, G |
author_sort |
Strong, C |
title |
Tropospheric Rossby wave breaking and the NAO/NAM |
title_short |
Tropospheric Rossby wave breaking and the NAO/NAM |
title_full |
Tropospheric Rossby wave breaking and the NAO/NAM |
title_fullStr |
Tropospheric Rossby wave breaking and the NAO/NAM |
title_full_unstemmed |
Tropospheric Rossby wave breaking and the NAO/NAM |
title_sort |
tropospheric rossby wave breaking and the nao/nam |
publisher |
eScholarship, University of California |
publishDate |
2008 |
url |
https://escholarship.org/uc/item/66v6z326 |
op_coverage |
2861 - 2876 |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_source |
Journal of the Atmospheric Sciences, vol 65, iss 9 |
op_relation |
qt66v6z326 https://escholarship.org/uc/item/66v6z326 |
op_rights |
CC-BY |
op_rightsnorm |
CC-BY |
_version_ |
1766134298466844672 |