Teleconnection between Summer NAO and East China Rainfall Variations: A Bridge Effect of the Tibetan Plateau
Teleconnection between Summer NAO and East China Rainfall Variations: A Bridge Effect of the Tibetan Plateau
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DOI：
10.1175/jcli-d-17-0413.1
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发表时间：
2017-12
影响因子：
4.9
通讯作者：
Ziqian Wang;Song Yang;N. Lau;A. Duan
中科院分区：
文献类型：
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作者：
Ziqian Wang;Song Yang;N. Lau;A. Duan
尽管北大西洋涛动(NAO)，特别是冬春季前期NAO对东亚夏季气候的影响已经得到了广泛的研究，但夏季NAO(SNO)和青藏高原(TP)与中国东部夏季降水的可能联系仍不清楚。研究表明，在年际尺度上，SNO与中国东部夏季降水的变化有显着的相关关系，而TP的热力强迫在这种欧亚遥相关中起到了中间桥梁作用。Snao主要通过大尺度波列来调节TP上的降水变率，而TP降水异常又导致局地非绝热加热的变化，从而激发Rossby波向下游地区传播。在对流层东北方向，几乎整个对流层都形成了一个异常的正压气旋，在中国北部产生了低层偏北气流异常。同时，TP加热也在中国南部诱发了低层偏南气流异常。异常的南北风在对流层低层汇合，加强了中国东部中部的夏季降水。与SNAO相比，TP热力强迫对欧亚遥相关区中国东部夏季降水的影响更为直接。
Although the impact of the North Atlantic Oscillation (NAO), especially the antecedent NAO in winter and spring, on East Asian summer climate has been studied extensively, the possible connection from the summer NAO (SNAO) and then the Tibetan Plateau (TP) to East China summer rainfall remains unclear. This study reveals that on interannual time scales the SNAO is significantly correlated with the variations of East China summer rainfall and the thermal forcing of the TP provides an intermediate bridge effect in this Eurasian teleconnection. The SNAO primarily regulates the rainfall variability over the TP through large-scale wave trains and the TP rainfall anomalies in turn lead to a change in local diabatic heating, which excites Rossby waves to the downstream regions. To the northeast of the TP, an anomalous barotropic cyclone is formed in the nearly entire troposphere, generating low-level northerly flow anomalies over northern China. Meanwhile, the TP heating also induces low-level southerly flow anomalies over southern China. The anomalous northerly and southerly winds converge in the lower troposphere, enhancing the summer rainfall over central East China. Compared to the SNAO, the TP thermal forcing exerts a more direct impact on the variations of East China summer rainfall in the Eurasian teleconnection discussed.