Influences of two types of El Niño events on wintertime aerosols over eastern China

After removing the aerosol optical depth (AOD) disturbance caused by long-term trend of anthropogenic emissions, the modulation effect of two types of El Niño on wintertime aerosol pollution and transport from the perspective of climatology is analyzed based on MERRA-2 reanalysis AOD and meteorological observation data. The results show that the EP El Niño events lead to positive AOD anomalies in most regions, and aggravate aerosol pollution especially from North China to Northeast China. And the CP El Niño events lead to significant "+-" bipolar distribution of AOD anomalies from south to north. Further analysis shows that although both types of El Niño event have the effect of weakening the wintertime wind and reducing aerosol transport from north to south, the weakening effect of CP El Niño events on horizontal flow field is not significant, especially in the northeastern region, where the significance level is lower than 90%. Furthermore, the effects of the two types on atmospheric vertical disturbance and wet removal of aerosols in the north are opposite, specifically, the EP El Niño events weaken convective available potential energy (CAPE), reduce precipitation, and weaken wet removal of aerosols; in contrast, the CP El Niño events enhance CAPE, increase precipitation and strengthen wet removal. In the south, heavy precipitation caused by significant EP El Niño events may be the main reason for the variation in regional aerosol pollution. The CP El Niño events aggravate local aerosol pollution in the middle and lower reaches of the Yangtze River mainly through weakening the wind speed.