Trend of surface solar radiation over China in relation to changing synoptic patterns

A comprehensive understanding of the relationship between atmospheric circulations and variations in surface solar radiation (SSR) is important for effectively utilizing solar resources and assessing climate change impacts. Here, we identify four synoptic patterns by T-mode principal component analysis method during 1980-2020 associated with the spatio-temporal variations of SSR in China, including geopotential height anomalies of west-high-east-low (Type 1), north-high-south-low (Type 2), east-low-west-high (Type 3), and north-low-south-high (Type 4). For the whole summer, there are more days of Type 1 and Type 2, accounting for 28.74 % and 28.58 % respectively. In particular, Type 1 experiences positive anomalies in cloud cover, water vapor and significantly reduced SSR reaching the Earth's surface. Type 2 pattern is characterized with low (high) anomalies of SSR over the Yangtze River Basin (Northeast China). And the north of the Yangtze River Basin is controlled by a northerly dry and cold airflow, leading to low cloudiness and precipitation with increased SSR reaching the ground in Type 3. Type 4 pattern exhibits a negative (positive) SSR anomalies in the Yellow River Basin (the Yangtze River Basin and Northeast China). Notably, the reduction of summer SSR in China since the 1980s is largely explained by the long-term changes of Type 2 and Type 4 synoptic patterns. These findings improve the understanding of the relationship between atmospheric circulations and SSR, and provide a scientific basis for policy planning of solar energy and dual-carbon targets in China.