福建省冬季持续低温事件多尺度特征及影响因子

Multi-scale Features and Impact Factors of Winter Persistent ColdEvents in Fujian Province

利用1960~2020年福建省66个国家气象站逐日观测资料、太平洋年代际振荡(PDO)及厄尔尼诺和南方涛动(ENSO)月指数、美国国家气象环境预报中心和国家大气研究中心(NCEP/NCAR)逐日再分析数据,采用功率谱分析、小波分解、合成分析等方法,讨论了福建省冬季持续低温事件的多尺度特征及影响因子,结果表明:(1)1961~2020年福建省冬季共出现114次持续低温事件,20世纪80年代中期以前为持续低温多发期,其后为少发期,持续低温的强度亦呈现前强后弱的分布;持续时间以5~11天居多,最长可达40天。(2)福建省冬季低温指数存在显著的10~20天和30~60天低频周期,年际尺度上以2~8年为显著周期。(3)福建省冬季持续低温事件和PDO、ENSO、热带大气季节内振荡及冷空气活动密切相关;PDO和ENSO为冷位相时,有利于持续低温的出现和持续时间偏长;当热带对流位于海洋大陆至西太平洋时,福建省冬季易出现持续低温事件;强盛的西伯利亚高压的存在,使得偏北气流可贯穿至华南南部,引发持续低温事件的发生。(4)对比不同持续时长低温事件的冷空气影响路径,“偏短型”“中等型”和“偏长型”事件分别以西路、东路和中路路径为主要特征。

Based on the daily observation data of 66 weather stations in Fujian Province from 1960 to 2020,namely,the Pacific Decadal Oscillation(PDO)monthly index,El Niño/Southern Oscillation(ENSO)monthly index,and National Centers for Environmental Prediction/National Center for Atmospheric Research daily reanalysis data,the multi-scale features and impact factors of winter persistent cold events are discussed using the power spectrum analysis,wavelet decomposition,and composition analysis.The results were as follows:(1)114 persistent cold events occurred between 1961 and 2020.These events frequently occurred with stronger mean intensity before the mid-80s;however,they decreased significantly with weaker mean intensity after that period.The prevalent duration was 5–11 days,even up to 40 days.(2)The winter cold index exists substantially in 10–20-day and 30–60-day low-frequency periods and in 2–8 years on the interannual scale.(3)The persistent cold events in winter are closely related to the ENSO events,atmospheric intraseasonal oscillations,and cold air activities.PDO and ENSO in the negative phases were favorable for the occurrence and duration of persistent cold events.When tropical convection prevailed in maritime continents and the western Pacific Ocean,persistent cold events occurred frequently.Furthermore,the cold northerly airflow guided by the strong Siberian High could reach the southern region of South China,which triggered the persistent cold event in Fujian Province.(4)By comparing the persistent cold events by different durations,the“short”,“medium”,and“long”events are characterized by the west,east,and middle cold air paths,respectively.