Articles | Volume 20, issue 12
31 Dec 2002
 | 31 Dec 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

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)