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.