Intensity of solar ultraviolet radiation and its implications for skin cancer.

The intensity of solar ultraviolet radiation (wavelength 307 nm) at ground level has been calculated using satellite measurements of atmospheric ozone. Ultraviolet levels in New Zealand are about 13% higher than those at similar latitudes in the northern hemisphere. Because of the clear atmosphere, peak daily summer irradiances may be only 50% less than those in tropical regions. From 35 degrees south (Auckland) to 45 degrees (Lauder, Central Otago), ultraviolet levels decrease by 5-10%. Peak ultraviolet irradiance in summer occurs at around 1330 local time. Over the last 10 years, calculated ultraviolet levels at Lauder have increased significantly, due to decreases in atmospheric ozone. These results are relevant to the high rates of skin cancer in New Zealand, and have implications for educational programmes relating to sun behavior and for future monitoring activities.