Ozone and Chlorine Monoxide over Antarctica from MLS (1/12/93 - 9/17/93)

The Microwave Limb Sounder (MLS) measures microwave emission from ozone and chlorine monoxide, a major ozone destroying radical. Right after UARS was launched, MLS began to measure large concentrations of chlorine monoxide over the south pole. These dramatic images clearly showed the extent of the south polar ozone destruction and confirmed the connection between man-made chlorine and the formation to the Antarctic ozone hole. Why is so much chlorine monoxide found over the Antarctic? UARS measurements have confirmed that CFCs enter the stratosphere in the tropics. As they rise above the ozone layer, ultraviolet molecules release chlorine, which then can react with methane to form hydrogen chloride. Chlorine can also react with ozone forming the radical chlorine monoxide. Chlorine monoxide then combines with the radical nitrogen dioxide to form stable chlorine nitrate. Chlorine nitrate and hydrogen chloride are called reservoir gases for the chlorine radical. These reservoir gases usually contain more than ninety percent of the chlorine in the lower stratosphere.

See http://svs.gsfc.nasa.gov/stories/UARS/index.html