On Problem of Nonlinear Symmetric Instability in Zonal Shear Flow

This paper is focused on the problem of nonlinear symmetric instability in a baroclinic basic flow. The limited amplitude characteristics of unsteady wave were investigated with the aid of equations of adiabatic,inviscid, nonlinear symmetric disturbance and a multi-scale singular perturbation technique. Evidence suggests that the limited amplitude of unsteady wave exhibits an oscillatory trend of its intensity: the amplitude of the symmetric disturbance displays periodical variation both in super- and sub-critical shear case, and the duration of the periods is related not only to the stability parameters of the basic field and wave properties but to the amplitude of initial disturbance and its time-varying change rate as well.