Modulation of the ENSO on Winter Aerosol Pollution in the Eastern Region of China

The modulation of the El Nino/Southern Oscillation (ENSO) on winter aerosol pollution (WAP) in the eastern region of China (ERC) was investigated from a climatological perspective. The results show that the weakened East Asian winter monsoon during El Nino events has an important influence on increased WAP in ERC, especially over northern China. The enhancement of the East Asian winter monsoon related to La Nina events reduces WAP in northeast, east, and south China but increases it in central and western China. Compared to northern China, anomalies in dynamic and thermodynamic conditions related to ENSO lead to more uncertainties in its effect on aerosol pollution over southern China. El Nino (La Nina) events tend to cause southwesterly (northeasterly) wind anomalies in winter southern China, along with the blocking effect of Nanling Mountains on southward (northward) air pollution, which is not (is) beneficial for the transport outside or dilution in local aerosols over southern China. Meanwhile, positive (negative) water vapor convergence and rainfall anomalies caused by El Nino (La Nina) are (are not) beneficial for the local removal of aerosols. The dominance of both factors determines the ENSO modulation on aerosols over southern China. An atmospheric global climate model largely reproduces the observed findings. Consistent with the observation, El Nino events exacerbate WAP in most of ERC, whereas La Nina ones reduce it except for western China. Plain Language Summary As a source of large-scale ocean-atmosphere interactions originating from the tropical Pacific, ENSO not only leads to anomalies in atmospheric circulation locally but also arouses global climatological anomalies. In this study, from a climatological perspective, the modulation of ENSO on winter aerosol pollution over Eastern China was investigated by diagnosis analysis and CAM5 simulation.