近年来,长三角霾事件频发,对人类和生态系统健康造成了严重危害,结果表明:热带印度洋12月海温与长三角1月霾日数呈显著正相关,特别是1999-2017年.12月,海温正异常加热上层空气,1月在对流层上层激发类似MatSuno-Gill模态和一系列Rossby波列,将信号传输至长三角,随后向下游日本海和阿留申群岛传播.长三角异常气旋中偏东风削弱东亚急流,影响该地气候.在近地面,SAT增加,偏南风盛行,风速减小,并伴有上游地区影响,有利于霾污染发生.上述分析结果在CESM-LE数值实验中得到很好的再现.“,”Haze events in the Yangtze River Delta (YRD) region have recently been occurring more frequently and with dramatic damages inflicted on human and ecosystem health.In this study,observational analyses and numerical experiments are used to investigate the meteorological conditions associated with haze pollution,with the main emphasis on the impacts of the preceding sea surface temperature (SST) in the tropical Indian Ocean (TIO).The results show that the December SST in the TIO has a significant positive correlation with the number of haze days in January over the YRD,especially during 1999-2017.In December,the positive SST anomalies in the TIO heat the overlying air,and then in the following January provoke a Matsuno-Gill-like pattern and a series of Rossby wave-like trains in the upper troposphere,transmitting signals to the YRD and downstream through the Sea of Japan and Aleutian Islands.The cyclonic anomalies in the YRD seem to significantly weaken the East Asian jet stream by means of anomalous easterlies,and subsequently affect the climate in the region.Near the surface,the increased surface air temperature and southerly winds,along with the decreased surface wind speed,accompanied by influences from upstream areas,are conducive to the occurrence of haze.These observational results were also reproduced well in CESM-LE simulations.