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| Titel |
On the time-scales of the downward propagation and of the tropospheric planetary wave response to the stratospheric circulation |
| VerfasserIn |
G. Nikulin, F. Lott |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 28, no. 2 ; Nr. 28, no. 2 (2010-02-01), S.339-351 |
| Datensatznummer |
250016765
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| Publikation (Nr.) |
 copernicus.org/angeo-28-339-2010.pdf |
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| Zusammenfassung |
| Three datasets (the NCEP-NCAR reanalysis, the ERA-40 reanalysis and the
LMDz-GCM), are used to analyze the relationships between large-scale
dynamics of the stratosphere and the tropospheric planetary waves during the
Northern Hemisphere (NH) winter. First, a cross-spectral analysis clarifies
the time scales at which downward propagation of stratospheric anomalies
occurs in the low-frequency band (that is at periods longer than 50 days).
At these periods the strength of the polar vortex, measured by the 20-hPa
Northern Annular Mode (NAM) index and the wave activity flux, measured by
the vertical component of the Eliassen-Palm flux (EPz) from both the
troposphere and the stratosphere, are significantly related with each other
and in lead-lag quadrature. While, in the low-frequency band of the downward
propagation, the EPz anomalies of the opposite sign around NAM extremes
drive the onset and decay of NAM events, we found that the EPz anomalies in
the troposphere, are significantly larger after stratospheric vortex
anomalies than at any time before. This marked difference in the troposphere
is related to planetary waves with zonal wavenumbers 1–3, showing that there
is a tropospheric planetary wave response to the earlier state of the
stratosphere at low frequencies. We also find that this effect is due to
anomalies in the EPz issued from the northern midlatitudes and polar
regions. |
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