Long-Term Changes of the Ultraviolet Radiation in China and its Relationship with Total Ozone and Precipitation

The new version (version 8) TOMS (Total Ozone Mapping Spectrometer) ozone and noontime erythemal ultraviolet (UV) irradiance products are used to analyze their long-term changes in this paper. It is shown that the summer UV irradiance has increased significantly from Central China to the northern and western parts of China, especially in Central China near Chongqing, Shaanxi, and Hubei provinces; whereas the UV irradiance has decreased significantly in the southern part of China, especially in South China. In July, when UV irradiance is at its maximum and hence when the most serious potential damage may happen, the results indicate an increase in the UV irradiance in Central China and the Yangtze River- Huaihe River valley and a decrease in South China and the eastern part of North China. At the same time, the total ozone amount is lower over China in summer with the most serious depletion occurring in Northeast China and Northwest China. It is found that the thinning of the ozone layer is not the main reason for the UV irradiance trend in the eastern and southern parts of China, but that the rainfall and the related cloud variations may dominate the long-term changes of the UV irradiance there. In addition, the future UV irradiance trend in China is also estimated.