Two Distinct Types of Extratropical Circulation Anomalies Associated with Cold Surges over the South China Sea
Two Distinct Types of Extratropical Circulation Anomalies Associated with Cold Surges over the South China Sea
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DOI：
10.1175/jcli-d-19-0041.1
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发表时间：
2019-07
影响因子：
4.9
通讯作者：
Bo Pang;R. Lu
中科院分区：
文献类型：
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作者：
Bo Pang;R. Lu
本文研究了南海冬季冷潮发生的温带环流异常。在925 hPa沿15°N方向在110°-117.5°E范围内的偏北风强度确定了浪涌事件。东亚两种不同的海平面气压异常模式在诱发南海寒潮中起着关键作用。据此，将寒潮事件分为两类。第一类冷潮主要表现为以中国和日本为中心的一对正距平和负距平，而第二类冷潮主要表现为东亚地区广泛和持续的正距平。第一类冷潮伴随着东亚槽加深和对流层中高层穿越欧亚大陆的罗斯比波前兆列，而后一类冷潮则没有。在这两种类型的冷潮之前，西伯利亚高压明显增强。然而，SLP倾向的诊断表明，增强与不同的物理过程有关。在第一类冷潮中，罗斯比波列有利于负涡度平流和冷平流，引起西伯利亚高压增强。而在第二类冷潮中，由于缺少罗斯比波列，涡度平流可以忽略不计，只有由异常西伯利亚高压引起的异常北风引起的对流层下层冷平流才有助于西伯利亚高压的进一步增强。
This study investigated the extratropical circulation anomalies responsible for cold surges over the South China Sea in winter. The surge events were identified by the intensity of northerly winds over 110°–117.5°E along 15°N at 925 hPa. Two distinct patterns of sea level pressure (SLP) anomalies in East Asia were found to have a crucial role in inducing cold surges over the South China Sea. Accordingly, the cold surge events were classified into two types. The first type of cold surge is characterized by a pair of SLP anomalies with positive and negative ones centered over China and Japan, respectively, whereas the second type of cold surge is characterized by widespread and persistent positive SLP anomalies over East Asia. Furthermore, the first type of cold surge is accompanied by a deepened East Asian trough and precursory Rossby wave trains across the Eurasian continent in the mid- and upper troposphere, but the latter is not. Prior to both types of the cold surges, the Siberian high is significantly intensified. However, diagnosis of the SLP tendency indicates that the intensification is related to different physical processes. In the first type of cold surge, the Rossby wave trains favor negative vorticity advection and cold advection, inducing intensification of the Siberian high. By contrast, in the second type of cold surge, vorticity advection can be ignored due to the lack of Rossby wave trains, and only the lower-tropospheric cold advection induced by anomalous northerly winds, resulting from the anomalous Siberian high, contributes to the further intensification of the Siberian high.