**6. References**

108 Solar Radiation

1960 1970 1980 1990 2000

The temporal variations in UV radiation using UV radiation and *Rs* data collected in Beijing over the period January 2005 to December 2010 were studied. The UV radiation levels increased gradually from spring reaching a peak in the summer, and gradually decreased to its lowest levels in winter. Its annual mean daily value was 0.39 ± 0.16 MJ m-2 d-1, and its lowest and highest daily values were 1.06 and 0.01 MJ m-2 d-1, respectively. Its highest daily value occurred in May and the lowest value occurred in December. The monthly mean daily value of the ratio, UV*/R*s, gradually increased from 2.7% in November to 3.7% in August,

The annual mean daily value of UV radiation from 1958-2005 was 0.46 MJ m-2 d-1. Over the latter half of the 20th century, there have been significant decreases in UV radiation (0.018

Measurements of total Ultraviolet radiation (UV), broadband global solar radiation (*R*S)*,*  reflective radiation, net radiation, and Photosynthetically active radiation from 2005 to 2010 in Beijing were used to determine temporal variation characteristics of UV in Beijing. The UV radiation levels increased gradually from spring reaching a peak in the summer, and then gradually declined to its lowest levels in winter. The annual mean daily value of UV radiation was 0.39 ± 0.16 MJ m-2 d-1, and the lowest and highest daily average UV radiation

after which it gradually decreased. The annual mean daily value of UV*/R*s was 3.1%.

Fig. 5. Long-term variation characteristics of annual average of Ultraviolet radiation for

per decade

Depearture

 5-year moving average Linear trend curve

linear trend=-0.018 MJ m-2

P 0.0001 <


**4. Conclusions** 

MJ m-2 d-1 per decade).

**5. Summary to the chapter** 

1958–2005. (Hu et al., 2010 b)

Daily average Ultraviolet radiation(MJ m-2

)

Annual

