The beta drift of baroclinic vortices. Part I: Adiabatic vortices

The dynamics of the movement of an initially axisymmetric baroclinic vortex embedded in an environment at rest on a beta plane is investigated with a three-dimensional primitive equation model. The study focuses on the motion and evolution of an adiabatic vortex and especially the manner in which vertical coupling of a tilted vortex influences its motion. The authors find that the vortex movement is determined by both the asymmetric flow over the vortex core associated with beta gyres and the flow associated with vertical projection of the tilted potential vorticity anomaly. The effects of vortex tilt can be large and complex. The secondary divergent circulation is found to be associated with the development of potential temperature anomalies required to maintain a balanced state. The processes involved strongly depend on the vertical structure, size, and intensity of the vortex together with external parameters such as the earth rotation and static stability of the environment. As a result, simple relationships between vortex motion and the vertical mean relative angular momentum are not always applicable.