中国东北与西北地区寒潮开始和结束的变化特征和影响机制

Characteristics and Influence Mechanisms of the Start and End of Cold Waves in Northeast and Northwest China

摘要: 全球变暖背景下，影响我国的寒潮发生了显著的变化，然而对于寒潮开始与结束区域特征和影响因子的认识仍显不足。本文基于1972~2021年站点资料，首先给出了一个刻画我国西北和东北地区寒潮开始和结束早晚的指数，进而分析了影响寒潮开始和结束的关键因子。结果表明，西伯利亚地区高空的环流异常是影响寒潮开始和结束早晚的重要因子。当秋季(春季)存在高压异常时，寒潮开始(结束)较晚(早)。异常高压的位置决定了其影响区域：当高压异常位于我国西北(东北)以北时，西北(东北)地区寒潮开始较早和结束较晚。秋季和春季异常高压的形成可分别归因于北太平洋和北大西洋海表面温度(SST)的异常。大气对上述区域SST异常的响应所形成的稳定环流异常作为波源激发纬向异常波列调制西伯利亚高空环流。并且，SST异常偏西或偏东伴随西伯利亚异常环流偏西或偏东，分别造成西北或东北寒潮开始、结束的早晚。由于上述海区SST存在明显的增暖趋势，因此我国东北和西北地区寒潮存在开始延后，结束提前的趋势。

Abstract: Under global warming, cold surges (CS) affecting China have significant changes; however, understanding of the regional characteristics of their start and end, as well as the influencing factors, remains limited. Based on station data from 1972~2021, this study first proposes an index to characterize the CS start date and end date in Northwest and Northeast China, and then investigates the key factors influencing these timings. The results show that upper-level geopotential height anomalies over Siberia play a crucial role in modulating the start and end of CS. The presence of a high-pressure anomaly in autumn (spring) is associated with a later start (earlier end) of CS. The location of the anomalous high determines the affected region: when the high-pressure anomaly lies to the north of Northwest (Northeast) China, CS in that region tend to start earlier and end later. The formation of the anomalous high pressure in autumn and spring can be attributed to sea surface temperature (SST) anomalies in the North Pacific and North Atlantic, respectively. The atmospheric response to SST anomalies in these regions generates quasi-stationary circulation anomalies that act as wave sources, exciting zonally oriented wave trains that modulate the upper-level circulation over Siberia. Moreover, when SST anomalies shift westward or eastward, the corresponding anomalous circulation over Siberia also shifts westward or eastward, resulting in earlier start and later end of CS in Northwest or Northeast China, respectively. Due to the significant warming trend in SST over the aforementioned oceanic regions, CS in Northeast and Northwest China exhibit a trend toward later start and earlier end.