平流层极涡异常下传影响东亚天气和气候的环流条件与机理

On the relation between stratosphere and troposphere, the traditional view is that stratosphere is a passive recipient of waves, energy and substances from weather systems in the underlying troposphere. While data analyses in the past two decades showed that the stratosphere can also influence the circulation and substances in the stratosphere, and can even be the dominant factor in the extreme events. For East Asian weather and climate system, the influences from stratosphere are also evident. Currently, the mechanism of the downward propagation of stratospheric anomalies is still not clear, especially, we don't know why some stratospheric anomaly events can have downward propagation and influence tropospheric circulation, while other anomaly events can't have downward propagation. Therefore, it has important scientific significance to study the circulation condition and mechanism of the downward propagation, and the downward influence of the climate and weather in East Asia by stratospheric polar vortex anomalies. By using data diagnosis, theory analysis and the new general circulation model with high resolution in the mid atmosphere, this study will help to understand the dynamical linkage between stratosphere and troposphere, and the mechanism of atmosphere teleconnection between high and mid-latitudes. This study will enrich the conception of East Asian monsoon system, and have important application values as it helps to select the key stratospheric factors and provides new perspective and predictors for the extended weather forecast in East Asia.

21世纪初以来的观测分析表明，在平流层和对流层的关系中，平流层不仅接受源自对流层的波动、能量和物质，而且会影响对流层的大气环流和化学成分，在极端情况时，还会成为影响对流层环流异常的主要因子。对于东亚天气气候而言，这种来自平流层的影响也非常明显。目前对平流层极涡异常下传的机理还不是很清楚，特别是并不清楚在什么样的环流条件下平流层异常会发生下传，从而影响东亚天气气候。因此本研究将利用国际上最新发展的平流层高分辨率的大气环流模式，结合数据诊断和理论分析，揭示平流层极涡异常下传影响东亚天气气候的环流条件和机理，从而形成一个全新的认识平流层和对流层之间关系的视角。这将为这一地区的天气气候预报提供全新的思路，对于了解上下层之间的动力联系，探索大气遥相关的发生机理，丰富东亚季风系统的内涵、以及提高东亚季风区天气气候预报的水平和时限，都有重要的科学意义和应用价值。

21世纪初以来的观测分析表明，在平流层和对流层的关系中，平流层不仅接受源自对流层的波动、能量和物质，而且会影响对流层的大气环流和化学成分，在极端情况时，还会成为影响对流层环流异常的主要因子。对于东亚天气气候而言，这种来自平流层的影响也非常明显。目前对平流层极涡异常下传的机理还不是很清楚，特别是并不清楚在什么样的环流条件下平流层异常会发生下传，从而影响东亚天气气候。因此本研究利用国际上最新发展的平流层高分辨率的大气环流模式，结合数据诊断和理论分析，分析了平流层极涡异常下传影响东亚天气气候的环流条件和机理，结果表明下传与不下传事件的过程中环流有较大差别，下传事件过程中，异常首先出现在平流层上层，随后异常加强并向极向下移动，不下传的过程中异常多首先出现在平流层中上层，异常加强并有向上移动的特点。下传事件和不下传事件中低层环流场的变化不一致。下传事件前后期有与北极涛动位相转变一致的特征出现；异常下传后东亚地区季风和温度有异常出现。两种不下传事件低层环流异常没有一致的变化形势。动力场上，下传过程和不下传过程前期折射指数达到零值后有反向变化，强极涡异常不下传事件前期折射指数减小而下传事件增加，不下传事件纬向流场更利于波动反射。不下传过程与下传过程相比而言折射指数变化更加平稳。本研究有助于形成一个全新的认识平流层和对流层之间关系的视角。这将为这一地区的天气气候预报提供全新的思路，对于了解上下层之间的动力联系，探索大气遥相关的发生机理，丰富东亚季风系统的内涵、以及提高东亚季风区天气气候预报的水平和时限，都有重要的科学意义和应用价值。