A new view on the trend of solar radiation in mainland China — based on the optimized empirical model

Abstract

As a kind of renewable energy, the development and utilization of solar energy is valued by many countries. To accurately provide a basis for the use of solar energy in mainland China, the optimized empirical model is adopted to analyze the variation trends and spatial patterns in solar radiation (SR) during 1961-2016 based on the data of 31 SR sites and 500 sunshine duration (SD) stations. The results indicate that there are obvious discrepancies in the variation trends of annual SR and SD during 1961-2016, with trend conversion occurring in 1992 (SR) and 1980 (SD), respectively. Overall, annual SR decreases at the rate of -3.68 MJ/m²•a in China. Notably, SR declines at the rate of -16.95 MJ/m²•a during 1961-1989 ("dimming" stage), while it increases at the rate of 5.34 MJ/m²•a for 1990-2016 ("brightening" period). In addition, all seasons show a tendency of dimming first and then brightening except for autumn. Compared with SD, SR is more sensitive to changes in pollution, leading to a marked recovery with the reduction of pollution after the 1990s. This study provides a new perspective for the trend difference between SR and SD after the 1990s.