Influence of an abnormally cold stratospheric polar vortex on the sub-regional PM2.5 anomaly in East Asia in March of 2021

This study investigates the critical role of meteorological variability, particularly polar vortex dynamics, in shaping PM2.5 anomaly patterns across sub-regions in East Asia. Following sudden stratospheric warming (SSW) in winter, East Asia experienced significant tropospheric transitions, including cooling-to-warming shifts. The strengthening of the Mongolian high, combined with tropospheric warming, altered lower tropospheric dynamics. Contrasting warming in Mongolia and cooling to the north intensified baroclinic instability, creating anomalous Mongolian cyclones for increased dust storm activity and higher PM2.5 levels. Elevated PM2.5 concentrations in eastern China, driven by substantial anthropogenic emissions, were dispersed by the divergent flow under the Mongolian high. Cyclones with increased baroclinic instability over southern and northeastern China contributed to precipitation, which led to negative anomaly variations of PM2.5 aerosols. Downwind regions like Korea saw elevated PM2.5 anomalies due to stable lower tropospheric conditions driven by the movement of the warmed Mongolian high.