两类厄尔尼诺事件对中国东部冬季气溶胶的影响

Influences of two types of El Ni?o events on wintertime aerosols over eastern China

利用MERRA-2再分析气溶胶光学厚度及气象观测资料,在剔除人为排放长期变化产生的气溶胶光学厚度扰动的基础上,从气候学角度探讨了两类厄尔尼诺事件对中国东部冬季气溶胶的影响。结果表明,东部型厄尔尼诺事件使绝大部分区域气溶胶光学厚度呈正异常分布,尤其对华北至东北的气溶胶污染加剧作用显著;而中部型厄尔尼诺事件使气溶胶光学厚度异常由南至北呈显著的"+-"双极型分布。进一步成因分析发现,虽然两类厄尔尼诺事件都具有削弱冬季风从而减弱北方气溶胶向南传输的作用,但中部型对水平流场的削弱作用不显著,尤其是东北地区没有通过90%的显著性检验。同时二者对北方大气垂直扰动和气溶胶的湿清除作用相反,其中东部型表现为大气垂直扰动和对流有效位能减弱,降水减少,湿清除减弱;而中部型则表现为垂直扰动和对流有效位能增强,降水增多,湿清除增强。对于南方,强东部型事件引发的强降水可能是产生该区域气溶胶污染影响不稳定的主因,而中部型则主要通过气流削弱作用加剧长江中下游地区气溶胶的局地污染。

After removing the aerosol optical depth （AOD） disturbance caused by long-term trend of anthropogenic emissions, the modulation effect of two types of E1 Nino 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 E1 Nino e- vents lead to positive AOD anomalies in most regions, and aggravate aerosol pollution especially from North China to Northeast China. And the CP E1 Nino events lead to significant ＂ ＋ - ＂ bipolar distribution of AOD anomalies from south to north. Fur- ther analysis shows that although both types of E1 Nino event have the effect of weakening the wintertime wind and reducing aerosol transport from north to south, the weakening effect of CP E1 Nino events on horizontal flow field is not significant, es- pecially 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 Nino events weaken convective available potential energy （CAPE）, reduce precipitation, and weaken wet removal of aerosols; in contrast, the CP E1 Nino events enhance CAPE, increase precipitation and strengthen wet removal. In the south, heavy precipitation caused by significant EP El Nino events may be the main reason for the variation in regional aerosol pollution. The CP El Nino events aggravate local aerosol pollution in the middle and lower reaches of the Yangtze River mainly through weakening the wind speed.