NONLINEAR STRUCTURES WITH MULTIVALUED (Q,PSI) RELATIONSHIPS - EXACT-SOLUTIONS OF THE BAROTROPIC VORTICITY EQUATION ON A SPHERE

Finite-amplitude solutions are sought to the Barotropic Vorticity Equa tion (BVE) on a sphere in the presence of realistic zonal flows. The n ew solutions are characterized by multivalued (q, psi) relationships, and can be constructed analytically. The resulting zonal flows and the (q, psi) scatter plots can be very close to climatology. Many observe d flow features of the persistent anomalies, like the midlatitude west erly jetstreams and splits as well as the well-known dipole-blocking s tructures can be well described in terms of these new solutions. It is suggested that the observed persistent anomalies in the atmosphere ma y be a manifestation of these solutions being resonantly excited throu gh thermal forcing.