Abstract
Stability properties of a localized disturbance in a zonally inhomogeneous basic flow is investigated in a non-divergent barotropic system on an f-plane. The basic flow is assumed to have uniform deformation and rotation matrices. For a disturbance which initially has an elliptical shape, the following result is obtained, which is an extension of Cai (1992): the elliptical disturbance elongated at an angle <π/4 along the contraction axis of the basic deformation matrix grows. In spite of the fact that the decrease of eccentricity has the effect of diminishing the disturbance energy, the increase of amplitude due to the conservation of enstrophy overwhelms it.
