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| Titel |
The summertime 12-h wind oscillation with zonal wavenumber s = 1 in the lower thermosphere over the South Pole |
| VerfasserIn |
Y. I. Portnyagin, J. M. Forbes, N. A. Makarov, E. G. Merzlyakov, S. Palo |
| 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 ; 16, no. 7 ; Nr. 16, no. 7, S.828-837 |
| Datensatznummer |
250013343
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| Publikation (Nr.) |
 copernicus.org/angeo-16-828-1998.pdf |
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| Zusammenfassung |
Meteor radar measurements of winds near 95 km
in four azimuth directions from the geographic South Pole are analyzed to reveal
characteristics of the 12-h oscillation with zonal wavenumber one (s=1).
The wind measurements are confined to the periods from 19 January 1995 through
26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s=1
oscillation is found to be a predominantly summertime phenomenon, and is
replaced in winter by a spectrum of oscillations with periods between 6 and 11.5
h. Both summers are characterized by minimum amplitudes (5–10 ms–1)
during early January and maxima (15–20 ms–1) in November and late
January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of
order 4–6 h occur during the course of the summer. In addition, there is
considerable day-to-day variability (±5–10 ms–1 in amplitude) with
distinct periods (i.e., ~5 days and ~8 days) which suggests modulation by
planetary-scale disturbances. A comparison of climatological data from Scott
Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near
78°S is s=1, but that at 68°S there is probably a mixture between s=1
and other zonal wavenumber oscillations (most probably s=2). The
mechanism responsible for the existence of the 12-h s=1 oscillation has
not yet been identified. Possible origins discussed herein include in situ
excitation, nonlinear interaction between the migrating semidiurnal tide and a
stationary s=1 feature, and thermal excitation in the troposphere.
Key words. Meteorology and atmospheric dynamics ·
Middle atmosphere dynamics · Thermospheric dynamics · Waves and tides |
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