where [[psi].sub.0] is the amplitude of perturbation of stream function [psi], k and l are the zonal and meridional wavenumbers, [beta] = [partial derivative]f/[partial derivative]y is the Rossby parameter
, and [u".sub.0] = [d.sup.2][u.sub.0]/[dy.sup.2].
In this [beta] = [[beta].sup.*][L.sup.2]/U, [[beta].sup.*] is Rossby parameter. U is characteristic velocity, L is characteristic length, and [L.sub.y] is the width of the beta-channel.
Recently, the Rossby parameters [beta] along with the changes of latitude were discussed by Luo  and [beta] plane approximation was obtained.