Internal waves of tidal periodicity

Two sets of internal wave data collected two years apart off Baja California have been analyzed for tidal energy. Although agreement was found for the semidiurnal periodicity, the diurnal oscillations were weak during the earlier measurements and strong during the later ones. Equilibrium tidal calculations suggest that the internal tide may be caused by a surface-tide-rough-bottom interaction in which the critical amplitude was exceeded in one case and not in the other.