Influence of Arctic Oscillation abnormalities on spatio-temporal haze distributions in China

This study investigates the impact of Arctic Oscillation (AO) abnormalities on the haze days in China for 57 winters from 1961 to 2017. The results reveal that that AO abnormalities mainly affected meteorological conditions and haze pollution in northern and central China, while their impact on the southeast coastal and Guangdong-Guangxi regions is not significant. During years with an abnormally high AO index (AOI) in winter, the number of haze days increased in northern and central China, especially in the Shanxi-Shandong-Hebei-Beijing-Tianjin and Hubei-Hunan-Henan-Jiangxi regions, while the number of haze days decreased during years of abnormally low AOI. When in the years of abnormally high AOI, the weakening of the East Asian trough caused the decrease of the meridional circulation and the increase of zonal winds compared with normal years. Furthermore, the weakening of the Siberian high pressure and the enhancement of the westerly circulation affected several meteorological factors, including the boundary layer height, surface temperature, wind speeds, and precipitations. These changes effectively inhibited the development of low-level vertical motion and the vertical diffusion of pollutants in the air, leading to the accumulation of haze pollution. The situation was the opposite for low AOI years, but the impact on the meteorological conditions was relatively weak compared to that during high AOI years. The impacts of the regional characteristics of AO abnormalities on the haze days are also investigated in this study.