2010-08-13: Ozone hole shift exposed South America to increased ultraviolet light

The ozone layer, which protects humans, plants, and animals from potentially damaging ultraviolet (UV) light from the Sun, develops a hole above Antarctica in September that typically lasts until early December. However, in November 2009, that hole shifted its position, leaving the southern tip of South America exposed to UV light at levels much greater than normal.
To characterize this event and to evaluate satellite monitoring capabilities, de Laat et al., 2010 analyzed satellite and ground-based measurements of ozone levels and the UV index (UVI). They found that the ozone column over southern South America was especially thin from 11 to 30 November 2009, and significantly higher UVI values were measured. Such abnormally low ozone levels sustained during a continuous period of 3 weeks had not been observed above southern South America at any time in the past 30 years, the researchers found. The high UVI values occurred over populated regions, meaning that humans had been exposed to increased levels of UV light. The scientists also note that the satellite-based and ground-based measurements agreed well, suggesting that satellite measurements can be valuable for monitoring ozone and UV radiation levels.

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Ozone column over the southern part of South America.
Average ozone colum over the southern part of South America in Dobson units (1 DU ~ 2.69 10^18 molecules/cm2) for 11-30 November 2009 (left) and the deviation with respect to the longyear average 1979-2008 (right).
Average UV-index over the southern part of South America for 11-30 November 2009 (left) and the deviation with respect to the longyear average 1979-2008 (right).