Influence of synoptic weather on aerosol variability over East Asia: Present and future

Aerosol variability is influenced by changes in emissions and atmospheric dynamics. The aim of this study is to identify the role of synoptic weather systems in affecting the aerosol variation over East Asia under future changes in atmospheric dynamics. First we investigate the influence of synoptic weather on aerosol optical depth (AOD) spatiotemporal variability using long-term observations from Moderate Resolution Imaging Spectroradiometer (MODIS). We demonstrate that the major synoptic weather patterns of each season are among the dominant factors that affect AOD variations. During spring and autumn, AOD variability is significantly influenced by dynamic transport under northeasterly (winter monsoon) or southwesterly (summer monsoon) conditions. In summer, the maximum anomaly of the AOD variability was associated with the occurrence of fronts and tropical cyclones near Taiwan. While in winter, cold surge was the major event controlling the AOD variability. As atmospheric dynamics are well connected with AOD interannual variability, the AOD predictability over East Asia is associated with the predictability of synoptic weather systems. We apply the high-resolution atmospheric model (HiRAM) to identify these weather systems in present climate and under future warming scenarios. Under future climate based on HiRAM, the occurrence of summer tropical cyclones decreases by 32%, and the autumn southwesterly pattern increases by 50%. Considering the frequency change in summer tropical cyclones and autumn southwestlies under future scenarios, this may lead to the accumulation of AOD over China during summer and autumn through dynamic transport. The results suggest that AOD variations in East Asia may change along with future changes in the large-scale circulation under global warming.