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The 16-day variation in tidal amplitudes at Grahamstown (33.3° S, 26.5° E)

S. B. Malinga, L. M. G. Poole
2002 Annales Geophysicae  
Meteor wind data at Grahamstown (33.3 • S, 26.5 • E) have been used to study the short-term (planetary scale) variations of the diurnal and semidiurnal tidal amplitudes at ∼ 90 km altitude. Wavelet multi-resolution and spectral techniques reveal that planetary periodicities of ∼ 10 and ∼ 16 days dominate the wave spectrum in the ∼ 2-20-day period range. The quasi-16-day oscillation is thought to be related to similar oscillations in the lower atmosphere. Also, there seems to be a link between
more » ... be a link between the winter/equinox 16-day oscillation in the mean flow and that in the semidiurnal tidal amplitudes. It is thought that this is probably due to either the coupling between the normal mode-mean flow interactions and the gravity wave-tidal interactions, or to direct nonlinear interactions between planetary waves and the tide. On the other hand, a comparison of the mean flow and the diurnal tide does not show evidence of correlation. Possible reasons for this disparity are discussed briefly.
doi:10.5194/angeo-20-2033-2002 fatcat:p5gbqwzjrrerjpznvv5ithiqs4