厄尔尼诺（El Nino）是发生在热带太平洋最显著的气候异常信号，对我国夏季降水异常有重要的指示意义。但是，由于赤道太平洋El Nino海温异常的复杂多样性，由此带来的气候效应也存在显著差别。这启示我们应该分型研究厄尔尼诺影响次年夏季东亚降水的机理。

大气科学学院温娜副教授团队的研究结果表明：不同型厄尔尼诺对我国次年夏季降水的影响存在显著差异，其根本原因是在不同型厄尔尼诺后延效应中起桥梁作用的关键海温不同。对东部型厄尔尼诺来说，长江中下游的异常降水是热带印度洋海盆一致模，北大西洋中部暖海温异常及Nino1,2区遗留暖海温异常共同作用的结果（图1a）；而混合型厄尔尼诺，其关键‘桥梁’海区:副热带东北太平洋的暖海温异常，热带太平洋初步发展的La Nina海温异常和热带南大西洋冷海温异常(图1b)造成了对华北和江淮流域偶极型降水异常；对中部型厄尔尼诺，它通过关键‘桥梁’海区热带北大西洋暖海温异常对我国长江和华南降水造成影响(图1c)。利用平衡反馈分析方法（EFA）和CESM模式热带太平洋海温异常的Pacemaker实验，我们进一步论证了这些不同型El Nino关键海温在其后延效应中‘桥梁’作用的可靠性。这为我们进一步认识不同型厄尔尼诺影响次年夏季东亚气候的物理机理提供参考。

Figure 1 Schematic showing different types of winter El Niño impacts on the following summer East Asian precipitation through their associated intermediate SST anomalies. a) EP El Niño. Excedent rainfall along the Yangtze River valley and its associated key circulation of the anomalous anticyclone over the western subtropical Pacific (the dark red dashed oval) are mainly caused by the winter EP El Niño – induced basin warming of the tropical Indian Ocean, the residual SST anomaly over the Niño1, 2 regions and the warm SST over the central North Atlantic in the following summer (pink shadings). b) MP El Niño. Precipitation anomalies show a dipolar pattern with dry conditions in the Jianghuai region and wet conditions in northern and northeastern China, which is mainly attributed to the anomalous cyclone over Northeast Asia (blue dashed oval) and the weak anomalous anticyclone over east-central China (dark red dashed circle). These precipitation and circulation anomalies are fundamentally caused by the MP El Niño’s intermediate SST anomalies in the following summer, such as the warm SST in the northeast subtropical Pacific (pink shading), the emerging La Niña in the eastern equatorial Pacific and the Niña-like anomaly in the southern tropical Atlantic (blue shadings). c) CP El Niño. Precipitation anomalies show wetness in the Yangtze-Huaihe River valley and dryness in southeast China, due to the weak low pressure over Northern China (blue dashed oval) and the westward shifted western Pacific subtropical high (dark red dashed circle). They are mainly caused by the winter CP El Niño – induced warm SST anomaly over the northern tropical Atlantic (pink shading). In the upper panels, the red and blue arrows indicate warm and cold advections. In the bottom panels, the red shadings indicate the different types of winter El Niño, and the yellow shadings denote the target area of this study.

Reference：

Wen N, Laurent Li, Yongsheng Hao. 2022, Response of East Asian Summer Precipitation to Intermediate SST Anomalies while El Niño Decays and Dependence on Type of Events[J]. Journal of Climate 35(12): 3845–3860. DOI: 10.1175/JCLI-D-21-0335.1