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The stratospheric polar vortex strength in spring determines to a great extent the duration and intensity of ozone depletion in the polar regions. The size of the Antarctic ozone hole usually reaches its maximum in September and then drops off during October and November. However, in 2015, a significant increase in the ozone hole area relative to climatological mean values was observed in October under the strong polar vortex conditions, and in 2002 its abnormal decrease was recorded as a result of the splitting of the polar vortex in September. A significant increase and decrease in temperature of the lower subtropical stratosphere in the spring of 2015 and 2002, which contributed to a corresponding increase and decrease in the stratospheric meridional temperature gradient during these years, was considered as a possible cause for the polar vortex strengthening in 2015 and its weakening in 2002.
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