Role of Subtropical Precipitation Anomalies in Maintaining the Summertime Meridional Teleconnection over the Western North Pacific and East Asia
Role of Subtropical Precipitation Anomalies in Maintaining the Summertime Meridional Teleconnection over the Western North Pacific and East Asia
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DOI：
10.1175/2008jcli2444.1
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发表时间：
2009-04-01
影响因子：
4.9
通讯作者：
Lin, Zhongda
中科院分区：
文献类型：
--
作者：
Lu, Riyu;Lin, Zhongda
西北太平洋和东亚夏季经向遥相关型(WNP-EA)在年际尺度上对东亚气候的影响起着主导作用。热带副热带降水的一种翘翘板模式与经向遥相关有关，而副热带降水异常以前被认为是与经向遥相关相关的异常环流的结果。然而，在这项研究中，作者认为副热带降水异常反过来又能显著影响大尺度环流，并可能是维持经向遥相关的关键。利用观测资料和再分析资料进行诊断分析表明，副热带降水异常较大的夏季，经向遥相关型较为明显。线性斜压模式的模拟结果表明，副热带热源相当于诊断的副热带正降水异常，在温带WNP-EA上空的对流层上部和下部都会产生与诊断的纬向风异常相似的纬向拉长的纬向风异常。模拟结果还表明，环流响应的水平和垂直结构对外加副热带热异常的位置和形状不敏感，这暗示了基本气流在环流响应中的重要作用。这项研究建议，对于东亚地区保密的动力季节预报，应该使用大气环流模式来捕捉WNP-EA的年际副热带降水变率和基本态气流的特征。
The meridional teleconnection patterns over the western North Pacific and East Asia (WNP-EA) during summer have a predominant role in affecting East Asian climate on the interannual time scale. A well-known seesaw pattern of tropical-subtropical precipitation is associated with the meridional teleconnection, and the subtropical precipitation anomaly has been previously viewed as a result of anomalous circulations associated with the teleconnection.In this study, however, the authors suggest that subtropical precipitation anomalies, in turn, can significantly affect large-scale circulations and may be crucial for maintenance of the meridional teleconnection. Diagnosis by using observational and reanalysis data indicates that the meridional teleconnection patterns are clearer in summers when the subtropical rainfall anomalies are greater. The simulated results by a linear baroclinic model indicate that a subtropical heat source, which is equivalent to the diagnosed positive subtropical precipitation anomaly, induces zonally elongated zonal wind anomalies that resemble the diagnosed ones in both the upper and lower troposphere over the extratropical WNP-EA. The simulated results also indicate that the horizontal and vertical structures of circulation responses are insensitive to the locations and shapes of imposed subtropical heat anomalies, which implies the important role of basic flow in circulation responses. This study suggests that, for confidential dynamical seasonal forecasting in East Asia, general circulation models should be required to capture the features of interannual subtropical rainfall variability and basic-state flows in WNP-EA.