Variation Characteristics and Establishment of EstimatingEquation for Ultraviolet Radiation in Yucheng, Shandong Province

The temporal variation of ultraviolet (UV) radiation and the ratio of UV radiation to broadband solar radiation were analyzed in Yucheng using the radiation observations of 2005-2011, and the estimating equation of UV radiation was established using the data of air temperature, precipitation, and dew point temperature. The results showed that the UV radiation has consistent variation characteristics with solar radiation; the cumulative value range was 0.10-1.20 MJ m^-2 d^-1, and the average value was 0.468 MJ m^-2 d^-1. The highest and lowest values of monthly UV radiation were measured in June and January, respectively. The highest value of daily UV radiation was measured at noon, and the lowest value occurred in the morning or at night. The range of the ratio of UV radiation to solar radiation was 0.023-0.046. The seasonal highest and lowest ratios of UV radiation to solar radiation occurred in summer and winter, respectively. The ratio reduced as the clearness index increased, and the ratio was relatively stable when the clearness index was greater than 0.5. Finally, a UV radiation estimating equation was established by using temperature and precipitation. The determination coefficient R² was 0.80, and the mean bias error was 0.19. There are 95% data the difference in observed and estimated values was less than 1 level. Thus, the equation is appropriate for estimation.