Non Linear Interaction between Long Waves in the Equatorial Waveguide

The change of sign of the Coriolis force in the Equator produces an e ective waveguide for a large class of long atmospheric waves Among these waves the longest and slowest are the nondispersive Kelvin and the dispersive Rossby and Yanai or mixed Rossby gravity waves These waves which have been observed in the troposphere and lower stratosphere are believed to play a sig ni cant role in the dynamics of the tropical atmosphere The most prominent waves observed are very long Kelvin waves with wavenumbers l and l i e inverse wavelength equal to the whole and a half of the circumference of the Earth and Yanai waves with l It has been proposed in that these waves force the stratosphere from below contributing to generate the quasi biennial oscillation of the mean wind in the tropical middle atmosphere The occurrence and persistence of these waves raise a number of important questions