Analysis Of Temporal And Spatial Characteristics And Influencing Factors Of UV Index In China

Ultraviolet light is very import for human health,ecology and climate.China has a vast territory and complex landforms,which leads to the quiet difference of spatial and temporal distribution and variation of ultraviolet index over China.Based on daily series datasets of UV index during the period from July 2002 to June 2016,this paper analyzes the temporal and spatial distribution characteristics over China firstly.Secondly,the paper discusses the annual change of UV index by calculating the Standard Deviation of different seasons over China and analyzes the characteristics of annual change using the EOF.Combined the Wavelet analysis,the periodic change of UV index is also studied in this paper.Thirdly,five cities were selected as typical area,analyzing the influencing of ozone and solar on the UV index using a multivariate linear regression model.The main results of this paper are as follow:1.The UV index map shows that the spatial distribution of UV index varies according longitude and latitude: increased from east to west of China and decrease from south to north of China.Based on the seasonal UV index maps,it concludes that UV index of summer was highest,followed by spring and autumn and the lowest was winter.The monthly mean of UV index over China is consistent with seasonal distribution.UV index began to increase in February and reached the maximum from June to August.From September,UV index began to decrease and reached the minimum in the next January.2.The annual change of UV index over China is gradually reduced from the southwest to the northeast,which the South China Sea and the Tibetan Plateau had the most annual change and the North China had the lest.The annual change of UV index shows different characteristics in different season,which UV index of Tibetan Plateau changed a lot in spring and South China Sea changed a lot in autumn.For other areas changed a lot in summer.The EOF results show that the annual change of UVI index over South China Sea,the southern Tibetan Plateau and southern Yunnan-Guizhou Plateau was sensitive in winter,which shows most sensitive change in November 2007.The northern Tibetan Plateau and Qinghai show most sensitive change in January 2011 and southern South China Sea was in July 2003.According the Wavelet analysis,the annual change of UV index over China mainly had three period,namely 5 years,1 years and 11 years.3.The results of multivariate linear regression show that the UV index over China mainly depends on the ozone and solar: the annual change of UV index influenced slightly with the solar radiation and declines strongly with the total ozone,which the change of total ozone accounted more than 80% for the variation of UV index.The change of total ozone is the main factor that causes the long term change of UV index.