Ground-based measurements of ultraviolet radiationin Yunnan,China

Measurements of surface ultraviolet radiation in two narrow bands centered at 254?nm and 297?nm were carried out from July 1999 to May 2000 at two sites,Lijiang (26°52′N,100°13′E) and Mengla (21°29′N,101°34′E),in Yunnan.In addition to the temporal and spatial variation of UV irradiance,preliminary effects of cloud cover and total ozone column on the surface ultraviolet radiation are analyzed.The study results show that the UV irradiances at 297?nm manifest a seasonal variation,which is high in summer and low in winter.The UV radiation is intenser at Lijiang than that at Mengla under the same sky condition,which may be caused by the effect of altitude.The cloud cover has a strong impact on the UV radiation,and a negative correlation between the UV irradiance and the total ozone column is exhibited after eliminating the influence of cloud cover,seasonal variation and random variation.