2017年冬季北京霾日极少的大尺度气候和环流背景:兼论“霾气候”预测研究

Unusually clear sky in Beijing during winter 2017 and the underlying large-scale climatic anomalies: With implication for “haze-climate” study

中文关键词:  北京霾  东亚冬季风  极端南风异常  关键区海温  “霾气候”预测

英文关键词:Beijing haze  East Asian winter monsoon  Extreme anomalous southerly  Sea surface temperature anomaly in the Northwestern Pacific  “Haze-climate” prediction

中文摘要:

      近年北京霾问题受到广泛关注。2017年冬季北京霾日显著偏少，同样令人瞩目。Pei等2018年提出一种影响北京持续性霾事件多寡的大尺度气候和环流背景机制，指出西北太平洋关键区（K区）海表温度距平起重要作用。文中据此对比分析2017和2016年冬季情形发现：2016年冬季K区偏暖，东亚冬季风系统偏弱，华北地区多异常偏南风距平，低层大气偏稳定，导致霾日偏多；而2017年情形恰好相反。这说明北京霾也受制于大尺度气候异常。进而简述现有研究存在的问题，就如何推进“霾气候”预测研究提出若干建议。

英文摘要:

      Haze over Beijing has received widespread attention in recent years. However, Beijing notably witnessed unusually few haze days in the winter 2017. In 2018, Pei et al proposed an observation-based mechanism linking the number of persistent haze events (PHE) in Beijing with large-scale climatic anomalies in surrounding regions, suggesting an important role of the sea surface temperature anomalies (SSTA) in a key region in the northwestern Pacific (K-region). This letter accordingly compares the large-scale winter climatic anomalies in 2017 with those in 2016, when Beijing encountered with the most serious haze in the observational history. In the winter 2016, the K-region was warmer than usual, giving rise to more frequent anomalous southerlies in North China and more stable atmospheric vertical structure, and hence more haze in Beijing. In the winter 2017, the K-region was cooler than usual with opposite atmospheric anomalies around, and hence less haze in Beijing. The analysis demonstrates that haze over Beijing is influenced by large-scale climatic anomalies. Current status of "haze-climate" studies in China is discussed and future research priorities are highlighted.