The spatial evolution of total ozone column (TOC) at mid to high southern latitudes and of the polar vortex in the lower stratosphere, for the period 1980-2000 shows an eastward rotation over this period. During this period the Antarctic polar vortex, undergoes a slow eastward rotation of the main axis of the monthly mean elliptic contour in late winter and spring. Similarly the climatological total ozone trough originally found in October over southern
The interannual evolution of TOC, after filtering the zonal mean solar cycle and QBO contributions, yields quasi-decadal oscillations in the rate of change total ozone south of 40S, which grows in magnitude between June and December. The spatial structure of this oscillarion is a large zonal wavelike, horseshoe structure with a comparatively small longitude segment in antiphase, which resembles the overall structure of the EOF1 field referred to as the Antarctic Oscillation or Southern Annular Mode. While SAM is defined as a fixed structure in space, with intensity variations over time, this horse-shoe structure however rotates eastward over time, in a manner similar to the polar vortex and the total ozone field over midlatitudes south of 40S.
These observations, given the resemblance between the spatial structures, would seem to suggest an apparent longitudinal evolution of the SAM over the two decades spanning the growth of the Antarctic ozone hole. In consequence the spatial evolution of the SAM structure of ECMWF ERA-40 geopotential height at 400 and 70hPa, representative of the upper troposphere and lower stratosphere, respectively, is analyzed to determine whether decadal changes similar to the detected TOC and stratospheric potential vorticity variability also occur.
The SAM structure evolution is presented, and the possible contribution to the spatial rotation of the TOC change discussed.