西伯利亚高压对南海冷涌的影响在1990s末的减弱及其机理

南海冷涌是北半球冬季典型的灾害性天气之一，是东亚冬季风重要的组成部分，对南海及周边地区的天气气候有重要的影响。西伯利亚高压是南海冷涌发展的主要影响因子，两者之间存在显著的负相关关系。但申请人初步分析的结果表明，这种相关性在1990s末前后发生了显著的年代际转变：在1990s末以前，西伯利亚高压对南海冷涌的影响较强；而在此之后，西伯利亚高压的影响显著减弱。本项目拟在此基础之上，首先对两者关系发生年代际变化的具体特征展开分析，从动力和热力过程诊断西伯利亚高压经向范围的年代际转变及其影响南海冷涌的物理机制；其次，阐述前后两个时段内影响南海冷涌环流因子的年代际差异，特别是热带环流（如：海温、对流等）对西伯利亚高压与南海冷涌关系的调制作用。因此，从内因和外因两个角度，揭示西伯利亚高压与南海冷涌的关系在1990s末以后显著减弱的原因。项目成果将有助于加深对东亚冬季风变异规律的认识。

Cold surge over the South China Sea (SCS) is one of the typical but severe weather phenomena during the boreal winter. As a crucial part of East Asian winter monsoon, cold surge has a great impact on weather and climate over the surrounding areas. Siberian high is the major factor and exhibits a prominent negative correlation with cold surges over the SCS. However, our preliminary results indicate that this relationship experiences a decadal change around late-1990s, i.e., the correlation coefficient is strong and significant before late-1990s, but becomes weak and insignificant after then. Based on this phenomenon, this project will investigate the features of this decadal change. Then, the underlying physical mechanisms would be explored by analyzing the dynamic and thermal processes associated with the meridional ranges of Siberian high. Further, the decadal changes of other factors, especially tropical circulations, e.g., sea surface temperature and convection, affecting cold surges over the SCS, would also be identified. The results of this project would be helpful for a better understanding of variability of East Asian winter monsoon.