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This shows MLS maps of lower stratospheric ClO and ozone on analogous `solar' days in the northern and southern hemispheres. These data are interpolated to the 465 K isentropic surface (approximately 20 km) and the color bars range linearly from 0 to 2.25 ppbv for ClO and 0 to 3.0 ppmv for ozone. Note there is more enhanced ClO in the northern hemisphere on 11 January 1992 than in the southern hemisphere on 11 July 1992. This is explained by the northern vortex being displaced more equatorwards than the southern vortex which brings air processed by PSCs into sunlight required to sustain enhanced ClO abundances and ozone depletion. Stronger dynamics (planetary waves) in the northern hemisphere cause the increased equatorward displacement of the northern vortex, but also keep northern temperatures warmer so that less PSC activation of chlorine occurs in the north. Note, in both the north and the south, the larger abundances of ozone (at this vertical level) in the polar vortex regions, even in the regions of enhanced ClO. Descent of ozone-rich air from above brings more ozone into the lower stratospheric polar vortex, and the net amount there (when ClO is enhanced) is a balance between increase due to influx and destruction due to chlorine. See Waters, et al.  for more discussion of these data.
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