Impact of Global Dimming and Brightening on Estimating Solar Radiation from Air Temperature in China

Estimation of solar radiation (SR) is important for energy plan, architectural design and solar energy systems. In China, it is necessary to explore estimating methods of SR because of the limited radiation measurement data. Based on meteorological data at 46 stations, temporal and spatial variations of annual SR and diurnal temperature range (DTR) were analyzed for different periods in this study. Results showed that average trends of DTR and SR were both dramatically declining for the global dimming period , but leveling off for the global brightening period (1991-2010), which indicated that DTR could be a reliable indicator of SR. Based on spatial analysis, SR trends were consistent with DTR trend at 43 stations during 1961 to 1990, while they were consistent for just 28 stations from 1991 to 2010. Then empirical coefficient Kr in the equation of estimating SR from DTR in different time scale and different periods in each station was calculated to assess the influence of changing SR on Kr. It can be permutated between monthly and annual Kr. However, there was significant but inconsistent variations in Kr for the period of 1991-2010 compared with 1961-1990, which suggested that global dimming and brightening had complicated effect on estimation of SR from DTR, with dramatic variability among different regions.