Abstract:

This study examined changes in solar radiation in the context of a warming and wetter climate regime in Xizang, with the aim of providing a reference for assessing the potential in the development and conservation of clean energy. Monthly sunshine duration and sunshine percentage, together with grain yield data were collected at 38 meteorological stations in Xizang from 1981 to 2024. Variations in annual and seasonal solar radiation (Q) and their spatiotemporal variation characteristics, as well as the influencing factors and their influence on grain yield, were analyzed in the same period based on the Ångstrom−Prescott empirical model and some statistical methods including linear tendency estimation, Pearson correlation coefficient, R/S analysis and Mann−Kendall test. The results showed that: (1) annual solar radiation exceeded 6300MJ·m⁻² at 81.5% of stations over Xizang from 1991 and 2020, meeting the highest abundance levels specified by meteorological industry standard in China, and making it highly suitable for solar energy development. The highest solar radiation were in summer, followed by that of in spring, with the lowest levels occurring in winter. (2) From 1981 to 2024, annual Q over Xizang decreased at a rate of −15.3MJ·m⁻²·10y⁻¹. Q decreased with 61%−66% of the stations during spring, summer and autumn, with the most notable annual reduction. Conversely, Q showed an increasing trend with 71% of the stations during winter. (3) Compared with the mean value of climate base period from 1991 to 2020, the average annual Q over Xizang was 4.5−114.8MJ·m⁻² higher from the 1980s to 2000s, especially in the 1980s. In the 2010s, it was 17.1MJ·m⁻² lower. (4) There was a high likelihood of continuous decline in Q during spring, summer and throughout the year in the future (2021−2050). However, the probability of a continuous decreased in Q during autumn and a continuous increase in Q during winter was lower. Abrupt changes in Q occurred during summer, winter and throughout the year in the mid to late 1990s. The turning points for Q during spring and autumn were around 2000 and 2012, respectively. (5) A significant negative correlation existed between Q and both total grain yield and yield per unit area during the crop growing season from 1981 to 2024. Specifically, Q in May had the most substantial impact on the grain yield, with a correlation that reached statistical significance at the 0.001 level. Consequently, a decrease in Q was beneficial, as it was associated with an increased grain yield. (6) The decrease in annual Q could be mainly attributed to the increase of the average low cloud cover over the past 44 years. Overall, the annual total solar radiation over Xizang showed a declining trend, and the likelihood of continuing this downward trajectory in the future was high in the 2010s. Nonetheless, the total solar radiation remains at the highest abundance levels, indicating significant potential for solar energy development. 

Key words: Solar total radiation, Solar resource, Spatiotemporal distribution, Linear trend, Climate mutation, Grain yield