Contr. Atmos. Phys. (1996), 69, pp. 333-347.
Isolated anomalies of high potential vorticity (PV) in the upper troposphere are usually interpreted as intrusions of stratospheric air. This paper investigates and compares the quasi-geostrophic dynamics of such anomalies in two different idealized models. The evolution of an initially elliptic vortex is calculated numerically with high horizontal resolution. Special emphasis is put on the stratosphere-troposphere exchange due to the cascade to small scales. The first model is a two-layer model with a PV anomaly in the upper layer, while the second makes use of Juckes's novel model for quasi-geostrophic tropopause dynamics. Both models differ significantly in various dynamic aspects like the rate of rotation and axisymmetrization of the core vortex, the location of the stagnation points, and the dynamical significance of the filaments. When viewing the high resolution vortex evolution with lower resolution, the filaments get lost in the low resolution view thus yielding an effective exchange of air from the stratosphere to the troposphere. This process operates on the advective time scale and reaches some saturation after the anomaly has been sufficiently axisymmetrized. The amount of air exchanged is similar in both models, but it sensitively depends on the shape of the initial vortex. A low resolution model may substantially overestimate this kind of stratosphere-troposphere exchange.