Predominant types of regional cold waves in North China and their historical changes

Abstract

Cold wave (CW) events in East Asia have a significant impact on the social economy, ecosystems, and human health. Based on daily CW records from October to March during 1980–2019 and K-means clustering, this study identified two types of regional CW (T1 and T2) in China. T1 regional CWs mainly struck Northeast China, whereas T2 regional CWs primarily affected the northern and eastern regions of China. Compared to T1, T2 regional CWs were more intense, lasted longer, and had a broader region of influence. During 1980–2019, there was a significant increase in the frequency of T1 regional CWs, while the frequency of T2 regional CWs showed no trend. Although amplification of the Siberian high was observed in both T1 and T2 regional CW events, there were differences in the wave train patterns in the middle troposphere between the two regional CWs. During T1 regional CW events, a wave train with negative–positive 500-hPa geopotential height anomalies over Siberia–Mongolia weakened the East Asian trough, causing an eastward movement of cold air from Siberia. The increasing trend of T1 regional CW frequency may be attributable to the linear trends of 500-hPa geopotential height caused by global warming. The wave train associated with T2 regional CW events formed ridge–trough–ridge circulation anomalies over the Ural Mountains, Mongolia, and North China. This led to a southeastward intrusion of the cold air. The conclusions of this paper indicate that the Siberian high amplification and mid-tropospheric wave train pattern should be jointly considered in forecasting regional CW events in China.摘要寒潮事件对东亚地区的社会经济, 生态系统和人体健康影响巨大. 根据1980−2019 年间10月至次年3月的每日寒潮记录和K-means聚类, 本文识别出了中国两种不同类型的区域性寒潮(T1 和 T2). T1区域性寒潮主要影响东北地区, T2区域性寒潮则主要影响华北和东部地区. 与T1区域性寒潮相比, T2区域性寒潮强度更强, 持续时间更长, 影响范围更广. 1980–2019年期间, T1区域性寒潮的频率显著增加, 而T2区域性寒潮的频率则没有趋势变化. T1和T2区域性寒潮事件均与西伯利亚高压增强有关, 然而与它们相关的对流层中层波列明显不同. 在T1区域性寒潮事件发生期间, 西伯利亚-蒙古上空出现负-正模态的500-hPa位势高度异常波列, 削弱了东亚大槽, 导致西伯利亚冷空气东移. T1区域寒潮频次增加趋势可能与全球变暖引起的500-hPa位势高度的线性趋势变化有关. 与T2区域寒潮事件相关的波列则在乌拉尔山脉, 蒙古和华北地区形成了脊-槽-脊环流异常, 导致冷空气向东南方向入侵. 本文得出结论, 由于两类区域寒潮影响不同, 西伯利亚高压增强和对流层中层波列模态在我国区域性寒潮事件的预报中应综合考虑.