The characteristics of net radiation (R n) (0.3–10 µm) in Lhasa and Haibei in the Tibetan Plateau were analyzed based on long-term in-situ measurements of surface radiation data. The monthly average of daily R n reached a minimum during the winter period followed by an increase until May and then a decline until January. This variation is consistent with solar activity. The annual mean daily total R n values were 0.92 MJ m−2 d−1 and 0.66 MJ m−2 d−1 in Lhasa and Haibei, respectively.
A relationship between R n and broadband solar radiation (R s) was demonstrated by a good linear correlation at the two sites. R n can be an accurate estimate from R s. The estimated R n values were similar to the observed values, and the relative deviations between the estimates and measurements of R n were 2.8% and 3.8% in Lhasa and Haibei, respectively. The application of the R n estimating model to other locations showed that it could provide acceptable estimated R n values from the R s data. Furthermore, we analyzed the influence of clouds on R n by different clear index (K s), defined as the ratio of R s to the extraterrestrial solar irradiance on a horizontal surface. The results indicate that more accurate results are associated with increased cloudy conditions. The influence of the albedo was also considered, but its inclusion in the model resulted in only a slight improvement. Because surface albedo is not usually measured, an expression based solely on global solar radiation could be of more extensive use.