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

S. B. Malinga (1) , L. M. G. Poole (1)

1 Department of Physics and Electronics

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 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.

Domaines: Océan, Atmosphère; Sciences de la Terre

S. B. Malinga, L. M. G. Poole. The 16-day variation in tidal amplitudes at Grahamstown (33.3° S, 26.5° E). Annales Geophysicae, 2002, 20 (12), pp.2033-2038. ⟨hal-00317456⟩