Variability in UVB Radiation in Beijing, China

The variation characteristics of Ultraviolet-B (UVB; 280315nm) radiation over Beijing were explored using measured data that were collected in Beijing from November 2010 to October 2011. Seasonal variations in UVB radiation and influence of ozone and clearness index on the ratio of UVB to broadband solar radiation (G) were investigated. The annual value of UVB radiation in Beijing is 6.37MJm2, and monthly average value ranges from 4.96 to 28.37kJm2d1. The maximum daily total UVB radiation ranges from 6.55kJm2d1 in November to 54.22kJm2d1 in July. The monthly minimum of daily total UVB radiation varies from 0.5kJm2d1 in February to 11.52kJm2d1 in July. The monthly average of the ratio of UVB radiation to G ranges from 0.007 to 0.017%, with an annual average value of 0.012%. The variation in slant ozone column causes annual cycle of the ratio UVB radiation to G, with maximum value in summer. In addition, clouds have a greater effect on G than UVB radiation. Thus, the ratio increases by more than 17% when the atmospheric conditions change from clear to cloudy.