Impacts Of Different Types And Intensities Of ENSO Events On Winter Aerosol Concentrations Over China

ENSO is a strong signal of interannual climate variability.The occurrence of an El Ni?o event may have an important impact on atmospheric pollutant concentrations in China through changes to the regional climate.This study quantitatively examines the differences among the effects of different types and intensities of El Ni?o events as well as different types of La Ni?a events on winter mean aerosol concentration and severe haze days in China,using an aerosol-climate coupled model.We also explore the impact of different types of El Ni?o events on haze days in northern China using observations.?1?It is found that the distribution of aerosol concentration in China is crucially affected by the atmospheric circulation anomalies in response to different El Ni?o events in winter.Central Pacific?CP?El Ni?o events lead to larger increases in the aerosol burden over the south of the Yangtze River,with the maximum change exceeding 1 mg m^-2.Moderate El Ni?o events induce large increases in surface aerosol concentrations over the entire eastern China,with the maximum increase reaching 0.5?g m^-3.In addition,A change in the south-north transport of aerosols caused by El Ni?o events play a dominate role in changing aerosol concentration and the occurrence of winter haze days in China.Moderate CP events lead to the largest increases in severe haze days over southern China,with the increase reaching 6.0 days.?2?There are obvious differences among the impacts of different types of La Ni?a events on winter mean aerosol concentrations.Especially in the eastern coast of China,Eastern Pacific?EP?La Ni?a events lead to an increase in aerosol concentration over this area,with the maximum increase exceeding 0.5?g m^-3(0.4 mg m^-2)in surface?column?concentration.However,CP events result in obvious decrease in aerosol concentration over the eastern coast of China,with the maximum value exceeding-0.5?g m^-3(-0.6 mg m^-2)in surface?column?concentration.?3?Statistical results show that two types of El Ni?o events have opposite impacts on the number of winter haze days in northern China.There are more sites,which shows the positive correlation between EP events and winter haze days,in northern China.Iep time series has a correlation coefficient of 0.16 with North China-averaged haze days.Furthermore,such events cause large increases in haze days in northern and northeastern China,with the maximum increase exceeding 2.4 days.Conversely,the sites,which shows the negative correlation between CP El Ni?o events and winter haze days,are dense in northern China and Icp time series has a correlation coefficient of-0.22 with North China-averaged haze days.CP events result in obvious decrease in haze days in northern and northeastern China,with the maximum decrease exceeding-2.4 days.