3. TECHNIQUE USED TO CALCULATE VERTICAL MOTIONS •

Atmospheric structure derived from satellite, multi-channel radiance data is used to calculate zonally-averaged vertical motions in the wintertime stratosphere of both hemispheres. The Northern Hemisphere calculations confirm the two-celled meridional circulation calculated by previous authors. The Southern Hemisphere results show a three-celled structure with descending motion over the South Pole. The variability of the mean meridional circulation in the Southern Hemi-sphere in relation to the presence or absence of a minor midwinter warming is also discussed. i ABSTRACT •••