摘要
2013年以来中国实施了一系列减排政策,大气污染物浓度明显下降,但由于气象条件的年际变化,中国PM_(2.5)(空气动力学直径小于_(2.5)µm的颗粒物)污染仍然存在.厄尔尼诺–南方涛动(ENSO)是调节大气–海洋系统年际变化的最强信号.本文研究了2014–2021年四次ENSO事件期间,中国四个特大城市群冬季PM_(2.5)浓度的变化.结果表明,在京津冀和汾渭平原地区,由于厄尔尼诺(拉尼娜)期间的偏南风(偏北风)异常有利于PM_(2.5)的积累(扩散),冬季PM_(2.5)浓度在厄尔尼诺年高于拉尼娜年.在珠三角地区,由于厄尔尼诺冬季水汽通量和降水的增加有利于大气中PM_(2.5)的湿清除,冬季PM_(2.5)浓度在厄尔尼诺年低于拉尼娜年.在环流和降水异常的综合作用下,ENSO对长三角地区PM_(2.5)浓度的影响难以预测,应逐案分析.
China has implemented a series of emission reduction policies since 2013,and the concentration of air pollutants has consequently decreased significantly.However,PM_(2.5)(particulate matter with an aerodynamic diameter less than_(2.5)μm)pollution still occurs in China in relation to the interannual variations in meteorological conditions.Considering that El Nino-Southern Oscillation(ENSO)is the strongest signalmodulating the interannual variation in the atmosphere-ocean system,in this study the authors investigate the variations in PM_(2.5)concentrations in four megacity clusters of China during the winter season associated with four individual ENSO events from 2014 to 2021.Results show that the wintertime PM_(2.5) concentrations in the Beijing-Tianjin-Hebei and Fenwei Plain regions during El Nino years are higher than those during La Nina years,which can be explained by the anomalous southerly(northerly)winds during El Nino(La Nina) favoring PM_(2.5) accumulation(diffusion).In the Pearl River Delta region,PM_(2.5)concentrations decrease in El Nino relative to La Nina years owing to the enhanced water vapor flux and precipitation,removing more PM_(2.5)from the atmosphere.The comprehensive effects of wind and precipitation anomalies lead to the unpredictability of the impacts of ENSO on PM_(2.5)over the Yangtze River Delta region,which should be analyzed case by case.
基金
This study was supported by the National Natural Science Foundation of China[grant number 41975159]
the National Key Research and Development Program of China[grant numbers 2020YFA0607803 and 2019YFA0606800].
