Sources and paths of extreme cold surges over China and their associated atmospheric circulations

Abstract

AbstractThe extreme cold surges (ECSs) are among the extreme weather events that affect China. Here, a total of 31 ECSs that occurred from 1962 to 2018 in China were identified using observed temperature data. In addition, we used the hybrid single‐particle Lagrangian integrated trajectory (HYSPLIT) model to trace their sources. And the atmospheric circulation of ECSs with different paths were investigated. The ECSs were classified to K‐type, B‐type and S‐type ECSs (which was subdivided into the S1‐type, S2‐type and S3‐type) according to their origins and entry locations into China. The S‐type ECSs occurred the most, accounting for 58.06%. The duration and temperature drop of the K‐type ECSs were higher than those of others. And K‐type and S1‐type ECSs mainly affected Northeast China, S2‐type ECSs mainly affected the regions east of 105° E. For decadal variation, Since the 1980s, ECSs frequency has decreased (especially only one ECS occurred in the 1980s), and K‐type and S2‐type ECSs disappeared. Different types of cold surges have different atmospheric circulation characteristics. The “positive–negative–positive” wave train structures of geopotential height anomalies at 500 hPa were very conducive to the formations of K‐type, B‐type and S3‐type ECSs. For K‐type and S1‐type ECSs, the cold high gradually moved south to Siberia, and combined with the cyclone anomalies, causing the cold air to enter China. Before the B‐type ECSs occurred, cold high appeared in the west of Xinjiang, which made the southeast cold air invade China. Regarding S1‐type and S2‐type ECSs, the negative anomalies over Eurasia from day −6 to day −4 and the subsequent cyclone anomalies at 850 hPa accompanied by the southeastward extension of cold high led to ECSs.