NIWA predicts high UV intensities this summer
The National Institute of Water & Atmospheric Research (NIWA) is predicting that peak ultraviolet index (UVI) this summer will be significantly higher than any of the last six years, and will be close to the all–time maximum observed in the summer of 1998–1999.
NIWA analysis shows it has been a record low ozone spring overall in the south. Springtime ozone amounts in middle (30°–60° S) and high (60°–90° S) latitudes of the southern hemisphere have been lower this year than in any other year since satellite observations began in 1979.
The World Meteorological Organization also reports that the Antarctic ozone hole reached near–record proportions this year.
NIWA scientist Dr Richard McKenzie says the predicted peak UVI varies from place to place. ‘Where I’m based at Lauder in Central Otago, we expect that the peak UVI will be close to 12 averaged over the five highest UV days in each summer month (December, January, and February). This is about five percent greater than the corresponding mean over the last few years, and is about 10 percent higher than when measurements began in the early 1990s.’ As usual, UVI values are expected to be higher in the north than in the south of the country. This is because ozone levels are lower and the sun reaches higher elevations in the north.
Dr McKenzie says NIWA’s UVI prediction is based on past statistical correlations between springtime ozone and peak UV radiation measured at Lauder in the following summer.
‘The low ozone expected over New Zealand is a consequence of the relatively high concentrations of ozone-depleting chemicals still present in the atmosphere, especially over Antarctica, in combination with a minimum in solar activity associated with the solar cycle and possible unusual transport of ozone in the stratosphere this year. We expect that over the decades ahead there will be a slow recovery in ozone.’
The most important variable factor affecting UVI is cloud cover, so the ultimate effect of the low ozone will be strongly influenced by the weather. NIWA provides UV forecasts to the general public via our website and to the media via the MetService.
