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Ann. Geophys., 20, 2027-2031, 2002
www.ann-geophys.net/20/2027/2002/
© European Geosciences Union 2002
The 16-day variation in the mean flow at Grahamstown (33.3° S, 26.5° E)
S. B. Malinga and L. M. G. Poole
Department of Physics & Electronics, Rhodes University, Grahamstown, 6140, South Africa
Correspondence to: L. M. G. Poole (g.poole@ru.ac.za)
Abstract. Data from the Grahamstown
(33.3° S, 26.5° E) meteor radar have been used to study the short-term
variations of the mean flow at ~ 90 km altitude. The results show considerable
variation characterised by a superposition of fluctuations on different
planetary time scales. Wavelet multi-resolution and spectral techniques reveal
that the quasi-16-day oscillation dominates the wave spectrum in the ~ 2–20-day
period range. This quasi-16-day oscillation, which is thought to be related to
a similar oscillation in the lower atmosphere, is found to be dominant in
winter and the equinoxes. However, it is sometimes significant in summer, which
could be due to cross-equatorial ducting and the selective transmissivity of
gravity waves.
Key words. Meteorology and
atmospheric dynamics (waves and tides)
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