The measurements of solar ultraviolet (UV) radiation at eighteen observation sites in Henan province, China
during 2005-2007 are analyzed to investigate the spatial distribution and temporal variation of UV irradiances. The
effects of cloud cover, visibility, and relative humidity on UV radiation are also quantified using regression techniques.
Results show that the annual averages of UV irradiances are high in central and southern Henan province. In winter,
the seasonal averages are high in northwestern Henan, while there are two high regions in the summer, one is resided
in the western part and the other is located in the eastern Henan, where two high centers can be identified. The
seasonal averages in summer and spring are higher than in fall and winter. The intensity of UV radiation is highly
related to total/low cloud cover, relative humidity, and visibility.