Low ozone air forecast over New Zealand

Press Release: NIWA Media Release 22 September 2006

New Zealand is expected to experience a ‘low ozone event’ on Sunday (24 September). The Royal Dutch Meteorological Institute and the European Space Agency are forecasting that a filament (a "rogue patch") of low ozone air currently circulating in the stratosphere around Antarctica will spin off and pass over much of New Zealand.

The agencies are forecasting about 23% less ozone over New Zealand than the average for this time of year. ‘Ozone values of about 275 Dobson Units are possible, whereas the September average at Lauder, Central Otago [lower part of South Island], is 358 Dobson Units,’ says Dr Greg Bodeker of the National Institute of Water & Atmospheric Research (NIWA). ‘The forecast suggests that the ozone values around noon on Sunday are likely to be a record low for this time of the year,’ says Dr Bodeker.

The forecast low ozone will push UV levels higher than usual for this time of year. According to NIWA, if the skies are clear, the forecast low ozone means that UV levels in the south of New Zealand are likely to increase from a typical September noon-time UV index of 4 to 5.5. In the north of the country, the noon UV index could be as high as 8 compared to the usual September value of around 6.5. A UV index of 8 is not extreme by standards of New Zealand’s mid-summer but it still represents very high UV levels. ‘If the sun is hidden by cloud, the risks are not as high, but when the weather is partly cloudy but people can still see the sun, the UV levels may go even higher than for clear skies,’ says Dr Bodeker.

The UV Index
Levels 1 & 2: The UV level is low. Low protection is needed and people can stay safely outside. Low – Low protection required. You can safely stay outside.
Levels 3 to 5: This indicates moderate UV levels. Moderate – Protection required when spending long periods in the sun.
Levels 6 & 7: Protection is essential. High – Protection essential. ‘Slip, slop, slap, and wrap.’
Levels 8 to 10: People should take great precaution. Very high – Seek shade between 11am and 4pm. ‘Slip, slop, slap, and wrap.’ Reapply sunscreen regularly.
Level 11+: This is regarded as extreme and full protection is essential. Extreme – Reschedule outdoor activities for early morning/evening. Shade is essential between 11am and 4pm. Reapply sunscreen regularly.

People should remember that you can get sun burnt even on cool days. Temperature is caused by the sun's infrared radiation, while sunburn is caused by UV radiation that cannot be felt.

[As an aside, Don looked into those Dobson units just to see how it compared to Colorado and Westminster/Denver/Boulder and he said it was pretty darn similar between the two. So all of you need to slip, slop, slap and wrap in summer yourselves! That's the national slogan because the UV rays from the sun are very intense here and the damage to the ozone layer directly affects much of this country]