COVID-19 Pandemic Reveals Distinct Impact of Aerosols on Surface Solar Radiation in China

With the abrupt and significant drop of PM2.5 concentrations during the lockdown in 2020, hourly direct radiation (R-dir) at surface substantially increased in East China, such as Zhengzhou, Wuhan and Baoshan, with the maximum enhancement of 86% at Wuhan. Most of these stations had decreased diffuse radiation (R-dif) except Zhengzhou. Zhengzhou had both enhanced R-dir and R-dif, as well as reduced but still high PM2.5 concentrations, indicating atmospheric particles were more scattering in this region. At Beijing and Harbin in North and Northeast China, intensification of aerosol pollution led to hourly R-dir (R-dif) falling (rising) up to -28% (59%) and -23% (40%), respectively. By contrast, surface solar radiation (SSR) in West China was also greatly influenced by the elevated dust/smoke layers, revealed by aerosol layer vertical distribution and the reduction of SSR and PM2.5 concentrations. This study highlighted the importance of aerosol optical properties and vertical structures in aerosol-radiation interactions.