Spatial distribution and temporal variation of ultraviolet Radiation in Henan province and the affecting factors

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.