Drift Velocity of Radiating Quasigeostrophic Vortices

Abstract

Because of the beta effect, quasigeostrophic monopole vortices propagate westward and excite Rossby waves. This wave radiation depletes the vortex energy, and causes cyclones to drift northward and anticylones southward (in the Northern Hemishpere). In the present work explicit solutions describing such radiating vortices are found by perturbation analysis, assuming the vortex amplitude to be large, and consequently the radiation to be a small perturbation. From these solutions the radiated energy is calculated and then used to obtain a simple expression for the meridional drift. The zonal drift is also modified by the wave radiation, but to calculate this component the complete explicit solution is not necessary; it is enough to consider the ratio of the loss of pseudoenergy to the loss of pseudomomentum.