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| Titel |
Signals of El Niño Modoki in the tropical tropopause layer and stratosphere |
| VerfasserIn |
F. Xie, J. Li, W. Tian, J. Feng, Y. Huo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-15), S.5259-5273 |
| Datensatznummer |
250011241
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| Publikation (Nr.) |
 copernicus.org/acp-12-5259-2012.pdf |
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| Zusammenfassung |
| The effects of El Niño Modoki events on the tropical tropopause layer
(TTL) and on the stratosphere were investigated using European Center for
Medium Range Weather Forecasting (ECMWF) reanalysis data, oceanic El
Niño indices, and general climate model outputs. El Niño Modoki
events tend to depress convective activities in the western and eastern
Pacific but enhance convective activities in the central and northern
Pacific. Consequently, during El Niño Modoki events, negative water
vapor anomalies occur in the western and eastern Pacific upper troposphere,
whereas there are positive anomalies in the central and northern Pacific
upper troposphere. The spatial patterns of the outgoing longwave radiation
(OLR) and upper tropospheric water vapor anomalies exhibit a tripolar form.
The empirical orthogonal function (EOF) analysis of the OLR and upper
tropospheric water vapor anomalies reveals that canonical El Niño events
are associated with the leading mode of the EOF, while El Niño Modoki
events correspond to the second mode. The composite analysis based on
ERA-interim data indicate that El Niño Modoki events have a reverse
effect on middle-high latitudes stratosphere, as compared with the effect of
typical El Niño events, i.e., the northern polar vortex is stronger and
colder but the southern polar vortex is weaker and warmer during El Niño
Modoki events. According to the simulation' results, we found that the
reverse effect on the middle-high latitudes stratosphere is resulted from a
complicated interaction between quasi-biennial oscillation (QBO) signal of
east phase and El Niño Modoki signal. This interaction is not a simply
linear overlay of QBO signal and El Niño Modoki signal in the
stratosphere, it is El Niño Modoki that leads to different tropospheric
zonal wind anomalies with QBO forcing from that caused by typical El
Niño, thus, the planetary wave propagation from troposphere to the
stratosphere during El Niño Modoki events is different from that during
canonical El Niño events. However, when QBO is in its west phase, El
Niño Modoki events have the same effect on middle-high latitudes
stratosphere as the typical El Niño events. Our simulations also suggest
that canonical El Niño and El Niño Modoki activities actually have
the same influence on the middle-high latitudes stratosphere when in the
absence of QBO forcing. |
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