El?Ni?o–Southern Oscillation (ENSO), a phenomenon of periodic changes in sea surface temperature in the equatorial central-eastern Pacific Ocean, is the strongest signal of interannual variability in the climate system with a quasi-period of 2–7?years. El?Ni?o events have been shown to have important influences on meteorological conditions in China. In this study, the impacts of El?Ni?o with different durations on aerosol concentrations and haze days during December–January–February (DJF) in China are quantitatively examined using the state-of-the-art Energy Exascale Earth System Model version 1 (E3SMv1). We find that PM 2.5 concentrations are increased by 1–2? μg?m ?3 in northeastern and southern China and decreased by up to 2.4? μg?m ?3 in central-eastern China during El?Ni?o events relative to the climatological means. Compared to long-duration (LD) El?Ni?o events, El?Ni?o with short duration (SD) but strong intensity causes northerly wind anomalies over central-eastern China, which is favorable for aerosol dispersion over this region. Moreover, the anomalous southeasterly winds weaken the wintertime prevailing northwesterly in northeastern China and facilitate aerosol transport from southern and southeast Asia, enhancing aerosol increase in northeastern China during SD El?Ni?o events relative to LD El?Ni?o events. In addition, the modulation effect on haze days by SD El?Ni?o events is 2–3 times more than that by LD El?Ni?o events in China. The aerosol variations during El?Ni?o events are mainly controlled by anomalous aerosol accumulation/dispersion and transport due to changes in atmospheric circulation, while El?Ni?o-induced precipitation change has little effect. The occurrence frequency of SD El?Ni?o events has been increasing significantly in recent decades, especially after the 1940s, suggesting that El?Ni?o with short duration has exerted an increasingly intense modulation on aerosol pollution in China over the past few decades.
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