Spatiotemporal characteristics of ultraviolet radiation in recent 54 years from measurements and reconstructions over the Tibetan Plateau

Based on measurements of ultraviolet radiation (UV) for the period of 2005–2014 that were obtained from the Chinese Ecosystem Research Network, we developed an efficient model to estimate UV radiation under various sky conditions. This model can provide an accurate reconstruction of UV radiation data with absolute mean bias error less than 9.65%. We combined this reconstruction model with a hybrid model to obtain the historical data set of daily UV radiation from 1961 to 2014 at 37 weather stations belonging to the China Meteorological Administration over the Tibetan Plateau (TP). Based on the historical data set, the spatial distribution and temporal variation of UV radiation over the TP region were discussed. The decreasing and increasing periods of ultraviolet radiation over the TP were significantly different from those over the entire China. There was an increasing trend in UV radiation over the TP from 1961 to 1983, followed by a decreasing one until 2014, while UV radiation decreased from 1961 to 1989 and then increased slightly after 1989 for the entire China. The average UV radiation values in the increasing and decreasing periods over the TP were 0.598 MJ · m−2 · d−1 and 0.594 MJ · m−2 · d−1, respectively. In addition, aerosol optical depth, column ozone, and cloud prevent approximately 7.13%, 1.31%, and 15.05% of UV radiation reaching the Earth's surface, respectively.