Tracer Transport in and around the Lower Stratospheric Antarctic Polar Vortex W. Feng and M.P. Chipperfield School of the Environment, University of Leeds, LS2 9JT, UK In September 1999 the APE-GAIA campaign used the M55 Geophysika aircraft to make tracer measurements at the edge of the Antarctic polar vortex. The Geophysika made 5 flights from Ushuaia (55S) towards the Antarctic and reached 70S. In-situ and remote instruments made measurements from around 10 km to 18 km. One of the aims of the mission was to investigate the extent of mixing across the vortex boundary as a function of altitude. In this poster/talk we will report on initial work which compares the measurements with output from a 3-D chemical transport model. The model has been run at a variety of resolutions and with different wind fields (UKMO and ECMWF) to investigate which configuration is best able to reproduce the observed vortex-edge tracer gradients and filaments. Diagnostics for the most realistic model version will then be used to quantify export of air from the polar vortex and its effects on the mid-latitude ozone budget.