1970—2013年中国东北地区强冷空气活动特征

利用1970-2013年NCEP-NCAR再分析资料以及中国基本基准825站地面气温均一化数据集,采用改进后的三维风速轨迹倒推方法,追踪了冬半年(10月至次年4月)入侵中国东北的强冷空气路径.结果表明:有西北路径230次,偏西路径75次,偏北路径101次.临近爆发前的环流演变导致三类冷气团大幅增温,削弱了不同源地的位温差异.偏西路径年频次减少幅度为0.26次/10a,而其他两类年频次没有明显变化趋势.相比之下,偏西路径强冷空气主要影响中国东北地区;西北路径强冷空气在东北地区能持续2.4d以上,并且对中国中东部以及南方地区的影响强于偏西路径;偏北路径强冷空气更易于在东北地区以及中国中东部地区造成异常低温事件,在南方地区可以形成持续2.8d以上的冷害.

Characteristics of Strong Cold Air Outbreaks in Northeast China During 1970 to 2013

With NCEP/NCAR reanalysis datasets and China basic data 825 station ground-temperature-homogenization datasets,an improved "three-dimensional wind speed trajectory inverse method"was adopted to trace cold air intrusion tracks that occurred during the winter half-years(i.e.,October to April)for the northeast China during the 43-year span between 1970 and 2013.The results showed that there were a total of 230 northwest tracks,75 west tracks,and 101 north tracks.The imminent circulation evolution pattern prior to outbreaks essentially caused three categories of cold air masses to undergo dramatic temperature increases,thereby reducing the impacts of source regional differences on the subject air masses.The measure of the annual frequency reduction in west tracks was determined to be 0.26 incidents every ten years,while there was no apparent trend for other tracks' annual frequencies.By contrast,west tracks mainly impacted Northeast China;northwest tracks could last more than 2.4 days in Northeast China,and it had more influence over the East and South China than the west tracks;north tracks probably brought abnormal low temperatures to Northeast and East China,and a temperature decreased to the southeast regions for over 2.8 consecutive days.