黑龙江省冬季极端寒冷指数的构建及年代际变化研究

The Construction of Extreme Cold Index of Winter and its Interdecadal Variation Analysis in Heilongjiang Province

利用1961—2020年黑龙江省冬季逐日气温资料,以连续5 d日平均气温低于一个标准差来判定极端冷事件,进而利用冷事件的持续天数和气温累计距平构建冬季极端寒冷指数(Extreme Cold Index of Winter,ECIW)。在此基础上深入研究了ECIW的年代际变化特征及其环流差异。结果表明:近60 a来黑龙江省ECIW呈显著上升趋势,且在1987年前后发生了年代际突变,突变后冬季冷事件强度显著减小。回归分析表明,突变前的1961—1985年,当ECIW强度偏强时,环流呈现北极涛动负位相和弱的欧亚遥相关型正位相分布特征,西北高东南低的环流配置下东亚中高纬环流经向度加大,影响黑龙江省的冷空气较强。而突变后的1991—2020年,环流呈现典型的欧亚遥相关型正位相分布,东亚温带急流显著偏弱,北高南低的配置下黑龙江上空低值系统活跃。对北极涛动、欧亚遥相关型、西伯利亚高压、东亚冬季风等指数与ECIW的相关和偏相关分析表明,北极涛动和欧亚遥相关型是影响ECIW的重要环流因子,1961—1985年北极涛动是主导因子,1991—2020年欧亚遥相关型是主导因子。

Based on the daily temperature data in Heilongjiang Province from 1961 to 2020,the extreme cold events are judged with the average temperature of consecutive 5 days being lower than one standard deviation,and then the Extreme Cold Index of Winter(ECIW)is constructed by using the duration and the cumulative temperature anomalies of cold events.On this basis,the interdecadal variation characteristics of the ECIW and its circulation differences are deeply studied.Results show that the ECIW in Heilongjiang Province is of a significant upward trend in the past 60 years,and an interdecadal abrupt change occurred around 1987,and the intensity of winter cold events decreased significantly after the abrupt change.Regression analysis reveals that before the abrupt change(1961—1985),when the ECIW intensity was stronger,the circulation showed a negative Arctic Oscillation phase and a weak Eurasian atmospheric teleconnection type positive phase distribution characteristics,under the circulation configuration of high northwest and low southeast,the meridional degree of the circulation in the middle and high latitudes of East Asia increases,and the cold air that affects Heilongjiang Province is stronger.After the abrupt change(1991—2020),the circulation showed a typical positive phase of Eurasian atmospheric teleconnection type,the East Asian temperate jet was significantly weaker,and the low-value system over Heilongjiang was active under the configuration.The correlation and partial correlation analysis of Arctic Oscillation,Eurasian atmospheric teleconnection type,Siberian high index,East Asian winter monsoon index with ECIW showed that Arctic Oscillation and Eurasian atmospheric teleconnection type are important circulation factors affecting ECIW,Arctic Oscillation is the dominant factor before the abrupt change,and Eurasian atmospheric teleconnection type is the dominant factor after the abrupt change.