Long-term variations of surface solar radiation in China from routine meteorological observations

Accurate observations of long-term surface solar radiation (SSR) are crucial for hydrological processes, agricultural production, and photovoltaic power generation. The main purpose of this study is to investigate the spatial-temporal variations and driving factors of SSR over mainland China. Firstly, ten selected models for estimating SSR were evaluated at 61 China Meteorological Administration (CMA) stations with SSR measurements. Then, the Yang's hybrid model (YHM) with the best model accuracy was used to construct a daily mean SSR dataset at 2474 CMA meteorological stations in China during 1961-2014. The results indicated that the annual mean SSR showed a fluctuating downward trend (-0.16 & times; 10-1 MJ m- 2 year-1) during 1961-2014 under all sky condition. The annual mean SSR showed dimming trend over mainland China during 1961-1989 and 1990-2005, while the annual mean SSR experienced an increasing trend (0.02 & times; 10-1 MJ m- 2 year-1) during 2005-2014 under all sky condition. Meanwhile, the annual mean SSR showed downward trend (-0.02 & times; 10-1 MJ m- 2 year-1) during 1980-2014 under clear sky condition, while an increasing trend (0.06 & times; 10-1 MJ m- 2 year-1) appeared under clear sky conditions from 2005 to 2014. The Qinghai-Tibet Plateau was always the area with the relatively higher SSR values, while the Sichuan Basin was generally the area with the relatively lower SSR values. Finally, the potential relationships between SSR and climate factors were analyzed. The result showed that the variation of annual mean SSR negatively correlates with the optical thickness of all cloud (TC) and the aerosol optical depth (AOD). The SSR had a significant positive correlation with sunshine duration (SD) under all sky conditions. The aerosol loading and SD were the primary factor of variation in clear sky SSR. The research will contribute to the studies related to climate change and land surface process.

Automated summary

The study examined the spatial-temporal variations and driving factors of surface solar radiation (SSR) over mainland China, finding that SSR exhibited fluctuating trends influenced by meteorological conditions and aerosol concentrations. The results contribute to the understanding of SSR patterns in the context of climate change and land surface processes.