黑龙江省冬季异常冷事件环流型和时序演变分析OA

Using daily mean temperature data from Heilongjiang Province and the NCEP/NCAR and ERA-Interim reanalysis datasets,the circulation patterns and temporal characteristics of 51 abnormal cold events that occurred in Heilongjiang Province during winters spanning 1961 to 2020 are analyzed.The key findings are as follows:When cold events occurred,the 500 hPa circulation was dominated by a"one-ridge-one-trough"pattern.Blocking circulation in the downstream region slowed the movement of the system,creating favorable conditions for the initiation and persistence of cold events.Hierarchical cluster analysis identified three distinct circulation patterns associated with these abnormal cold events.Among the total 428 days on which abnormal cold events occurred,Type 1,Type 2,and Type 3 circulation patterns accounted for 35.7%,52.8%,and 21.5%of the days,respectively.The three circulation patterns shared a common feature:in the 500 hPa geopotential height field,Heilongjiang Province lay within an area of negative anomalies,while an anomalous positive anomaly center was present in the downstream Pacific region.However,they differed in one critical aspect:the Western Siberian re-gion(upstream of Heilongjiang Province)exhibited anomalous circulation centers with opposite polarities(posi-tive and negative).This suggests that the intensified East Asian Trough and downstream blocking circulation were the dominant drivers of abnormal cold events in Heilongjiang Province,whereas the upstream circulation system played a secondary role.In terms of intensity,Type 2 circulation pattern featured a stronger high-pressure ridge in the upstream Western Siberian region;Type 3 was characterized by a more robust downstream blocking circulation;and Type 1 had weaker anomalous circulation centers overall.Of the 51 abnormal cold events,28 were dominated by a single circulation pattern,20 experienced one circulation pattern transition,and 3 underwent two transitions.Additionally,during 43 of these events(representing 84.3%of the total),one circulation pattern corresponded to one cold center.Temporal analysis of the three circulation patterns revealed that anomalous cir-culation signals emerged relatively early.Specifically,the earliest anomalous signals for Type 1,Type 2,and Type 3 patterns appeared 6 days,9 days,and 12 days prior to the onset of the respective patterns.This finding provides valuable insights for short-term to medium-term weather forecasting and extended-range climate prediction.