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| Titel |
Observational evidence of quasi-27-day oscillation propagating from the lower atmosphere to the mesosphere over 20° N |
| VerfasserIn |
K. M. Huang, A. Z. Liu, S. D. Zhang, F. Yi, C. M. Huang, Q. Gan, Y. Gong, Y. H. Zhang, R. Wang |
| 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 ; 33, no. 10 ; Nr. 33, no. 10 (2015-10-30), S.1321-1330 |
| Datensatznummer |
250121262
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| Publikation (Nr.) |
 copernicus.org/angeo-33-1321-2015.pdf |
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| Zusammenfassung |
| By using meteor radar, radiosonde and satellite
observations over 20° N and NCEP/NCAR reanalysis data during 81
days from 22 December 2004 to 12 March 2005, a quasi-27-day oscillation
propagating from the troposphere to the mesosphere is reported. A pronounced
27-day periodicity is observed in the raw zonal wind from meteor radar.
Spectral analysis shows that the oscillation also occurs in the meridional
wind and temperature and propagates westward with wavenumber s = 1; thus the
oscillation is of Rossby wave type. The oscillation attains a large
amplitude of about 12 m s−1 in the eastward wind shear region of the
troposphere. When the wind shear reverses, its amplitude rapidly decays, and
the background wind gradually evolves to be westward. However, the
oscillation can penetrate through the weak westward wind field due to its
relatively large phase speed. After this, the oscillation restrengthens with
its upward propagation and reaches about 20 m s−1 in the mesosphere.
Reanalysis data show that the oscillation can propagate to the mid and high
latitudes from the low latitudes and has large amplitudes over there. There
is another interesting phenomenon that a quasi-46-day oscillation appears
simultaneously in the troposphere, but it cannot penetrate through the
westward wind field because of its smaller phase speed. In the observational
interval, a quasi-27-day periodicity in outgoing long-wave radiation (OLR)
and specific humidity is found in a latitudinal zone of 5–20° N.
Thus the quasi-27-day oscillation may be an atmospheric response to forcing
due to the convective activity with a period of about 27 days in the tropical
region. |
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