Stability of Rectilinear Geostrophic Vortices in Stationary Equilibrium

A hemispherical barotropic model of global-3cale atmospheric motions is studied in a planar approximation using three K (Bessel)-vortices of equal strength y and length scale g" to represent the sub-tropical semipermanent high pressure systems. In equilibrium tl-3se anticyclonic vortices are equally spaced on a latit ade circle of radius a. One K -vortex of strength -y is used o 0 ' o to simulate the polar (cyclonic) vortex; 7 is choren so that the equilibriun. configuration remains stations ry with respect to the rotating earth. Over the rangt of the length parameter 0 _< (»ca) _< 5, two distinct st£ ble regimes are found: 1) a "soft"-vorcex regime, 0 < Ua) < (« .a) = 1.44763516 and 2) a "hard"-vo) tex (climatological) regime, ic > K • The nonlinear p£ rt of this stability investigation has been carried out rainly by numerical computation.