两类ENSO对东亚夏季风环流垂直耦合模态的影响机理

ENSO是热带海气耦合系统最突出的年际信号，是预测东亚夏季风降水变率的重要影响因子之一。南亚高压和西太平洋副热带高压是东亚夏季风高低层环流的主要成员和水汽载体，两者通过垂直“齿轮式”耦合存在相互作用，其年际变化直接影响中国夏季雨带的位置。由于东部型和中部型ENSO的演变机制及其引起的大气遥相关差异，导致其对东亚夏季风环流和降水异常的影响也显著不同。为此，本项目拟围绕两类ENSO对东亚夏季风环流垂直耦合模态的影响差异这一核心问题，利用资料分析、动力诊断和数值模拟等技术手段，系统分析两类ENSO本质差异及其时间稳定性，结合热带印度洋海温“接力”作用，剖析两类ENSO对东亚夏季风环流“齿轮式”耦合模态影响的主要物理过程。通过以上研究揭示中国夏季降水多模态年际变化主要成因，为我国短期气候预测提供新的科学依据。

El Niño-Southern Oscillation (ENSO) is the most robust interannual signal in tropical air-sea interactions, and it has been regarded as the first factor the seasonal prediction of East Asian summer monsoon (EASM) rainfall. Evidences suggest that the Western North Pacific subtropical high (WNPSH) and the South Asian high (SAH) are two important dynamic wheels of the EASM circulations, their vertical coupling may directly modulate summer rain-belts in China. However, the climate impacts of the Eastern-Pacific (EP) and Central-Pacific (CP) ENSO on the EASM are rather distinct, due to their different evolution mechanisms and remote forcings. In this regard, this project intends to address the different climate impacts of the EP and CP ENSO on the vertical coupling mode of EASM. We firstly investigate the essential differences of the two types of ENSO and their time stability, with the help of data analysis, dynamic diagnosis, as well as the numerical simulation. Taking into account of “recharge/discharge” roles of the Indian Ocean sea surface temperature, the linkages between the two types of ENSO and the coupling wheels of the EASM, as well as the possible physical processes will be explored. Finally, we will reveal the interannual diversity of EASM rainfall and their physical mechanisms in the framework of two types of ENSO impacts. We wish this study may deepen the understanding of the EASM, related to the ENSO diversity, and provide some valuable suggestions for the summer climate seasonal prediction in China.