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| Titel |
Connection between weak stratospheric vortex events and the Pacific Decadal Oscillation |
| VerfasserIn |
Sung-Ho Woo, Mi-Kyung Sung, Seok-Woo Son, Jong-Seong Kug |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106533
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| Publikation (Nr.) |
 EGU/EGU2015-6209.pdf |
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| Zusammenfassung |
| The possible effect of the Pacific Decadal Oscillation (PDO) on the morphology of weak stratospheric vortex (WSV) events in the Northern Hemisphere winter is examined by analyzing long-term reanalysis data. The WSV events, which are defined when negative polar-cap geopotential height anomalies at 50 hPa fall below their wintertime 10th percentile, are found to occur more frequently during the positive phase of the PDO (+PDO) than during the negative phase (-PDO). More importantly, during +PDO, vortex displacement events are more popular. This contrasts with –PDO during which vortex split events are more common. This difference is closely linked to the difference in wave forcing. It is found that while +PDO WSV events are primarily driven by wavenumber-one forcing with rather minor contribution of wavenumber-two forcing, –PDO WSV events are mainly driven by wavenumber-two forcing.
This difference in wave driving partly results from the PDO-related tropospheric circulation anomalies over the North Pacific. In terms of linear interference argument, wavenumber-one component of +PDO-related anomalies constructively interferes with climatological waves. However, destructively interference is found for –PDO-related anomalies. The enhanced wavenumber-two forcing during -PDO is likely caused by the enhanced low-frequency variability over the Alaska that results from the poleward shift of the Pacific jet in response to -PDO. |
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