摘要:本文总结了近年来关于我国冬季大范围持续性极端低温事件（EPECE）及其对应的欧亚大陆大型斜脊斜槽系统的研究成果。EPECE和普通寒潮是冬季影响我国的两类不同时间尺度大型冷空气活动，对它们的异同点进行梳理和深入理解是非常必要的。最新研究进展可概括为如下：（1）基于极端低温站点的范围和极端低温过程的持续性特点，客观界定了我国冬季EPECE。近年来的研究表明，欧亚大陆大型斜脊斜槽系统是冬季EPECE形成和维持的主要关键环流系统。同时，鉴于大型斜脊斜槽系统的重要应用意义，建立了客观识别方法。（2）从前兆信号、环流演变、阻塞高压和反气旋式波破碎活动的角度，揭示了EPECE和普通寒潮事件之间的关键区别。全国类EPECE的发生具有一周之前的前兆信号，而普通寒潮并不存在这么早的前兆信号。EPECE以从乌拉尔山到东北亚的广阔区域的阻塞高压活动为关键特征，而普通寒潮则主要以区域性阻塞高压为其主要特征。这两类事件对应的阻塞高压活动的差异可由天气尺度波破碎活动的差异加以解释。（3）最新的研究解释了大型斜脊斜槽系统形成和维持的动力学机理。基本流场对位涡扰动的正压作用是大型斜脊斜槽系统的形成和维持最重要的动力学机制。基本流场通过变形场作功和线性平流使大型扰动维持和向下游发展。与阻塞高压不同，非线性作用并非大型斜脊斜槽系统维持的主要原因。
关键词:大范围持续性低温事件/
大型斜脊斜槽/
寒潮/
阻塞高压/
波破碎
Abstract:In this paper, studies on the wintertime extensive and persistent extreme cold event (EPECE) in China and the corresponding large-scale tilted ridge and trough (LSTRT) systems over the Eurasian continent are systematically reviewed. The EPECE and the ordinary cold wave events are two types of large-scale cold air activity influencing China in winter, but with different time scales. It is necessary to sort out and understand their similarities and differences. The latest research progresses in this area can be summarized as follows:(1) Based on the scope of extremely low temperature stations and the persistence characteristics of low temperature processes, the winter EPECEs in China are objectively defined. It has been revealed that the LSTRT is the key circulation system of the EPECE over the Eurasian continent. Due to the operational importance, an objective identification method of the LSTRT has been proposed in a recent study. (2) Key differences between the EPECE and ordinary cold wave events are revealed in recent studies from the perspectives of precursory signals, circulation evolutions, blocking activities and synoptic scale wave breaking features. The occurrence of a countrywide EPECE has a precursor signal about one week in advance, but an ordinary cold wave event does not have such an early precursor signal. An EPECE is characterized by the blocking activity over a broad region from the Ural Mountains to Northeast Asia, while an ordinary cold wave is usually characterized by regional blocking activity. The difference in blocking activities between these two types of cold event can be explained by differences in their corresponding synoptic scale wave breaking activities. (3) The underlying mechanism for the formation and maintenance of LSTRT system is revealed. The barotropic effect of the basic flow field on the potential vorticity disturbances is the most important dynamic factor for the formation and maintenance of LSTRT. Through deformation effect, the basic flow field works on the large-scale disturbance to keep its amplitude and simultaneously extend it to downstream region through linear advection effect. In contrast to the situation of regional blocking, the nonlinear effect is not the main factor for the maintenance of the LSTRT system.
Key words:Extensive and persistent extreme cold events (EPECE)/
Large-scale tilted ridge and trough (LSTRT)/
Cold wave/
Blocking/
Wave breaking
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