自20世纪90年代以来，冬季北半球中纬度地区极寒天气事件频发，研究其机制和物理过程具有重要科学和社会意义。本项目基于北大西洋涛动（NAO）和阻塞环流之间的协同作用特征，从天气尺度角度揭示欧亚地区和北美地区低频模态间的协同作用对极寒天气的影响机制。拟利用观测和再分析资料，从辨识NAO和阻塞环流之间协同作用特征入手，探讨形成这种协同作用特征的大气背景条件，并对主要的协同环流进行归类并分析其对应的天气气候效应。进一步，通过对极寒天气事件进行统计和归类，找出其与NAO和阻塞协同环流之间可能的联系，探讨协同环流对极寒天气的可能影响。最后，结合背景西风条件以及特定协同环流的形成机制和物理过程，揭示NAO和阻塞协同环流对中纬度地区极寒天气的影响机制和物理图像。上述研究获得的有关物理过程和图像有利于我们从天气尺度角度系统认识NAO和阻塞的协同作用对极寒天气的影响。

The increasing frequency of wintertime extreme weather in the Northern Hemisphere have been observed since 1990s.It has great scientific and social significances to study their mechanisms and physical processes. Based on the collaborative interaction between North Atlantic Oscillation (NAO) and blocking over Eurasia and North America, this research project plans to reveal the physical processes that the collaborative interaction circulation motivates the extreme weather from the perspective of synoptic scale. By using observational and reanalysis dataset, the characteristics of the collaborative interaction between NAO and blocking as well as the corresponding background westerly condition will be identified. In addition, the collaborative interaction events will be further classified according to their components and characteristics. The extreme events at mid-latitude in the Northern Hemisphere are identified and then try to find out the possible relationship between extreme events and collaborative interaction system. Moreover, by examining the background westerly condition and the physical process that hides behind the collaborative interaction events, the physical image and mechanism that the collaborative interaction events affect the extreme events will be discussed.