Stationary zonal-wavenumber-two Rossby-wave condition
= Stationary zonal-wavenumber-two Rossby-wave condition
In the uniform-current beta-plane model, $U=\beta/(k_2^2+l^2)$ with $k_2=2/(a\cos\phi)$. This is a model-dependent balance between eastward advection and westward intrinsic propagation, not a unique speed set by zonal wavenumber alone.