During the CRISTA 2 campaign in August 1997 the Antarctic polar vortex according to UK Met Office (UKMO) data was strong but temporarily disturbed by planetary waves. This winter was in general warmer than the five previous winters; nevertheless, temperatures cold enough to allow the formation of nitric acid trihydrate (NAT) and ice particles occurred throughout the period from mid-June to the end of August. The cold vortex core developed in the potential temperature range from 400 to 700 K at the beginning of the winter, initially centered at 600 K but slowly progressing downward to 450 K in the subsequent months. The vortex disturbances showed a clear zonal wave number 1 and 2 pattern. This planetary wave activity caused a strong day-to-day fluctuation of the vortex shape. During August when the second Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA 2) mission took place the vortex was elongated toward the southern Atlantic Ocean, processing slowly eastward. The perturbation of the vortex was associated with air masses transported from middle and low latitudes into the polar region in small-scale streamers. Similarly, tongues of vortex air peeled off the vortex edge and moved equatorward, enhancing the exchange between polar regions and the tropics. In addition, the disturbance of the vortex led to the generation of filaments at the inner side of the vortex edge, thus covering the vortex interior with small-scale structures. A comparison between CRISTA observations and potential vorticity derived from UKMO data shows discrepancies concerning small-scale structures. High-resolution potential vorticity fields calculated from reverse domain filling trajectory simulations on isentropic surfaces based on horizontal winds from UKMO analyses and vertical motion from diabatic calculations are much more consistent with the measurements. Both observation and reverse domain filling (RDF) simulations show the strong atmospheric variability of this period of unusual enhanced planetary wave activity in the Southern Hemisphere.