The effects of El Niño–Southern Oscillation on the winter haze pollution of China

Abstract. It has been reported in previous studies that El Niño–Southern Oscillation (ENSO) influenced not only the summer monsoon, but also the winter monsoon over East Asia. This contains some clues that ENSO may affect the winter haze pollution of China, which has become a serious problem in recent decades, through influencing the winter climate of East Asia. In this work, we explored the effects of ENSO on the winter (from December to February) haze pollution of China statistically and numerically. Statistical results revealed that the haze days of southern China tended to be fewer (more) than normal in El Niño (La Niña) winter, whereas the relationships between the winter haze days of northern and eastern China and ENSO were not significant. Results from numerical simulations also showed that ENSO influenced the winter atmospheric anthropogenic aerosol content over southern China more obviously than it did over northern and eastern China. Under the emission level of aerosols for the year 2010, winter atmospheric anthropogenic aerosol content over southern China was generally greater (less) than normal in El Niño (La Niña) winter. This was because the transport of aerosols from South and Southeast Asia to southern China was enhanced (weakened), which masked the better (worse) scavenging conditions for aerosols in El Niño (La Niña) winter. The frequency distribution of the simulated daily surface concentrations of aerosols over southern China indicated that the region tended to have fewer clean and moderate (heavy) haze days, but more heavy (moderate) haze days in El Niño (La Niña) winter.