Preliminary UV, ozone and cloud comparison between Southern and Northern Hemisphere, sub-tropical latitude sites during 1996/1997

Abstract

This paper compares 12 months of daily erythemal weighted ultraviolet (DUV) radiation, ozone and cloud cover data between two dissimilar, sub-tropical latitude sites during two months of 1996, and all of 1997, containing an overlapping 10 month period. The sites were an urban Southern Hemisphere site (27.42°S) and a Northern Hemisphere park land (29.3°N). The daily averages for the respective 12 month periods were found to be 3.6 kJ/ m 2 , 27 DU (Dobson units) and 4 okta for the Southern Hemisphere site and 3.6 kJ/ m 2, 282 DU and 3 okta for the Northern Hemisphere site. Although the maximum daily DUV level was higher by a nominal 12% at the Southern Hemisphere site compared to the Northern Hemisphere site, the Northern Hemisphere National Park site had a daily DUV level comparable to that of the Southern Hemisphere urban site. The average ozone was higher by 2.5% at the Northern Hemisphere site compared to the Southern Hemisphere site and the cloud cover was higher by 1 okta at the Southern Hemisphere site. The higher cloud cover, and its higher correlation to the changes in DUV at the Southern Hemisphere site, and the higher altitude of the Northern Hemisphere site, is believed to be the major causes for these similar daily average DUV levels.