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| Titel |
Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM |
| VerfasserIn |
M. M. Hurwitz, I.-S. Song, L. D. Oman, P. A. Newman, A. M. Molod, S. M. Frith, J. E. Nielsen |
| 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 ; 11, no. 18 ; Nr. 11, no. 18 (2011-09-19), S.9659-9669 |
| Datensatznummer |
250010086
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| Publikation (Nr.) |
 copernicus.org/acp-11-9659-2011.pdf |
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| Zusammenfassung |
The Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS
V2 CCM) is used to investigate the response of the Antarctic stratosphere to
(1) warm pool El Niño (WPEN) events and (2) the sensitivity of this
response to the phase of the QBO. A new formulation of the GEOS V2 CCM
includes an improved general circulation model and an internally generated
quasi-biennial oscillation (QBO). Two 50-yr time-slice simulations are
forced by repeating annual cycles of sea surface temperatures and sea ice
concentrations composited from observed WPEN and neutral ENSO (ENSON)
events. In these simulations, greenhouse gas and ozone-depleting substance
concentrations represent the present-day climate. The modelled responses to
WPEN, and to the phase of the QBO during WPEN, are compared with NASA's
Modern Era Retrospective-Analysis for Research and Applications (MERRA)
reanalysis.
WPEN events enhance poleward tropospheric planetary wave activity in the
central South Pacific region during austral spring, leading to relative
warming of the Antarctic lower stratosphere in November/December. During the
easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed
4–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative
to ENSON.
In the recent past, the response to WPEN events was sensitive to the phase
of the QBO: the enhancement in planetary wave driving and the lower
stratospheric warming signal were mainly associated with WPEN events
coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response
to WPEN events is insensitive to the phase of the QBO: the modelled response
is always easterly QBO-like. The QBO signal does not extend far enough into
the lower stratosphere and upper troposphere to modulate convection and thus
planetary wave activity in the south central Pacific. |
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