一个北半球冬季大气低频流型的形成和维持机制

申请人最近揭示了北半球冬季一个新的大气低频流型C2（Bao and Wallace 2015 JAS)；C2流型对冬季从北美到欧洲的大范围天气气候异常有重要影响，而不同于以往所认识的遥相关型。本项目拟研究的关键科学问题是C2流型的形成和维持机制。我们将基于大气动力学基本理论，利用1957-2015年ERA再分析资料、海温强迫的全球大气环流模式和一个全球正压大气模式分析热带热源强迫及其敏感性、副热带急流的动力效应、中纬度定常波和天气尺度波传播、平流层与对流层动力耦合在C2流型的形成和维持上所起的作用和机制。本项目将试图解释新发现的大气低频流型是如何形成和维持的，这对我们认识北半球冬季大尺度气候变率有重要科学意义，对延伸期预报和短期气候预测具有潜在应用价值。

Bao and Wallace (2015) identified four Northern Hemisphere wintertime flow regimes using SOM cluster analysis. One of them, C2 pattern, has significant impacts on the weather and climate over most North America and western Europe. The key issue of this project is to investigate the formation and maintenance mechanism of the C2 flow regime. Based on the atmospheric dynamic basic theory, ERA datasets during 1957-2015, a global atmospheric circulation model along with a baratropic atmospheric model, we intend to analyze the tropical thermal forcing and its sensitivity. We will study the dynamical effects of subtropical jet, stationary waves and synoptic waves propagation in mid-latitude on the formation and maintenance of the C2 pattern. The potential role of stratosphere-troposphere dynamical coupling is also to be considered. The project aims at explaining how the C2 pattern is formed and maintained which is important for us to understand the large scale climate variability of the Northern Hemisphere in boreal winter and has potential value for dynamical extended-range forecast and climate prediction.