Investigating the all-sky surface solar radiation and its influencing factors in the Yangtze River Basin in recent four decades

Abstract This study uses the second Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) reanalysis product to analyze the all-sky surface solar radiation (SSR) over the Yangtze River basin (YRB) and the quantitative impact of main factors from 1980 to 2018. Radiation data and multiple atmospheric factors were inputted into a multiple linear regression model. The regression results showed that aerosols and total clouds were the dominant factors affecting annual SSR variation. The aerosol radiative effect (ARE) and cloud radiative effect (CRE) were then calculated to quantify the effects of aerosols and clouds on SSR based on the MERRA-2 dataset. The average ARE and CRE in the YRB was −10.70 ± 2.01 and −47.92 ± 2.31 W/m2, respectively, which means that clouds attenuate SSR more than aerosols. SSR showed a general decline throughout the region (−0.156 W/m2 per year) and decreased significantly in the Sichuan Basin (SB, −0.242 W/m2 per year). The enhanced weakening of the radiative cooling effect of aerosols and clouds determines the decrease in the SSR. In Central China (CC), ARE had significantly enhanced (−0.297 W/m2 per year) and CRE had significantly weakened (0.207 W/m2 per year). From 1980 to 1990, the SSR in the Western Sichuan Plateau (WSP) increased by 0.329 W/m2 per year, affected by the decrease in aerosol and cloud, in which low clouds and dust aerosols played an important role. The SSR in SB was reduced due to the significant increase in sulfate, black carbon, and organic carbon aerosols. And aerosols in Yangtze River Delta (YRD) have important effects on SSR, while clouds were dominant for CC. From 1991 to 2018, the dominant factor influencing the SSR in WSP, SB, and CC was cloud, while the SSR in YRD was mainly determined by aerosols. From 2008 to 2018, the SSR in WSP significantly decreased by −1.188 W/m2 per year, mainly due to the increase in clouds. During this period, the SSR in YRD increases by 0.220 W/m2 per year, largely from the decrease of aerosols.