Increased Solar Radiation due to the Clean Air Action in Eastern and Central China during 2014-2019

Abstract:

China has implemented strict air pollution control measures since 2013, resulting in a 30–50% decline in annual mean PM_2.5 concentrations. However, it remains unclear how the recent air quality improvements affect the trends of surface solar radiation (SSR). In this study, we use ground-based and satellite-based observations to quantify the trends of SSR over eastern and central China (ECC), and to identify the aerosol and clouds radiative effect (ARE and CRE) contributing to the SSR trends. We show that the annual mean SSR in ECC has similar upward trends of 0.6–1.2 Wm^-2yr^-1 for 2014-2019 based on both observations from the Chinese Ecosystem Research Network (CERN) and the Clouds and the Earth’s Radiant Energy System (CERES). Besides, the SSR trends show obvious seasonal discrepancy, with a strong increasing trend in summer but a slight decreasing trend in winter. We further find that the trends of annual ARE have larger magnitude than those of CRE, reflecting that the stronger declining trends of ARE plays a dominant role in producing the increasing annual SSR trends. The ARE exhibits decreasing trends in both summer and winter, but the decrease is much stronger in summer mainly because of a larger reduction in summertime aerosol loading. In winter, CRE shows a strong increasing trend, which, together with the weak decreasing trends in ARE, explains the downward trends of wintertime SSR. The SSR, ARE, and CRE trends are consistent in spatial pattern. These results indicate an important role of air pollution control measures in regulating surface radiation, which has important implications for regional hydrology cycle and photovoltaic power generation.