Southern Hemisphere, stratospheric ozone depletion

FIGURE 20.29 This false color image shows total stratospheric ozone amounts over the southern hemisphere for September 24, 2006, as recorded by the Ozone Monitoring Instrument (OMI) mounted on the Aura spacecraft. The dramatic depletion of the ozone layer over Antarctica is revealed with the help of the false color scale at the bottom of the figure. Ozone amounts are commonly expressed in Dobson units 300 Dobson units is a typical global average over the course of a year. The size of the Antarctic ozone hole was near a record high and the levels of ozone near a record low on this date. 

In the Southern Hemisphere, chlorine activation leads to a remarkable springtime decrease in ozone that has come to be known as the Antarctic ozone hole on the other hand, polar ozone depletion is considerably smaller in the Arctic. The difference arises from the weaker wave driving of the stratospheric circulation of the Southern Hemisphere. As seen in Fig. 9, wave amplitudes are smaller in the the Southern Hemisphere, and so is wave driving, to the point that the southern polar jet persists much longer into the spring than its northern counterpart. The delayed breakdown of the southern polar vortex allows ozone loss to continue throughout the months of September and October. In the Northern Hemisphere, on the other hand, the conditions necessary for ozone loss usually disappear in mid- to late March, when the northern polar vortex breaks down. 

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