STEADY 2-LAYER VORTICES ON THE BETA-PLANE

Monopolar vortices are studied in the framework of the quasigeostrophi c two-layer equations. Steady, eastward-travelling vortex solutions wi th a baroclinic vertical structure and closed streamlines in both laye rs are obtained by perturbation analysis. The radial profile is essent ially arbitrary in the region of closed streamlines. Westward-travelli ng vortices with a similar structure radiate barotropic waves, and are therefore unsteady. The propagation velocity of the vortices is essen tially determined by the 'hetonic' mechanism, i.e. by the horizontal s hift between the upper- and lower-layer vortices. Their dynamics are s tudied qualitatively, and it is concluded that eastward-travelling vor tices are stable, whereas those travelling westward are unstable.