ON THE BAROTROPIC INSTABILITY OF LARGE SCALE VORTICES

By using the linearized barotropic vorticity equation in polar coordinates the stability of pertur-bations on a large scale circular basic flow is transformed into a generalized eigenvalue problem,yielding the relationship between the growth rate of the amplitude of perturbations and the az-imuthal wave number. Then, numerical experiments whose integration time is 60 model hours areperformed in terms of a quasi-geostrophic barotropic model in Cartesian coordinates using the per-turbation stream function field of unstable mode superimposed on a strong and weak circular basicflows as the initial fields. The experimental results reveal that the amplitudes of the initial pertur-bations in the model atmosphere grow with time. The amplitude of the perturbations superimposedon the strong circular basic flow grows quicker and forms a spiral-band-like structure.

ON THE BAROTROPIC INSTABILITY OF LARGE SCALE VORTICES

By using the linearized barotropic vorticity equation in polar coordinates the stability of pertur- bations on a large scale circular basic flow is transformed into a generalized eigenvalue problem, yielding the relationship between the growth rate of the amplitude of perturbations and the az- imuthal wave number. Then, numerical experiments whose integration time is 60 model hours are performed in terms of a quasi-geostrophic barotropic model in Cartesian coordinates using the per- turbation stream function field of unstable mode superimposed on a strong and weak circular basic flows as the initial fields. The experimental results reveal that the amplitudes of the initial pertur- bations in the model atmosphere grow with time. The amplitude of the perturbations superimposed on the strong circular basic flow grows quicker and forms a spiral-band-like structure.