北太平洋风暴轴的气候特征及其变化的初步研究

本文使用ECMWF再分析网格点资料(ERA-40),分析了不同季节和不同高度层上北太平洋风暴轴(天气尺度瞬变扰动活动)的气候特征及其时间演变规律。分析表明,气候平均而言,北太平洋风暴轴冬季强且偏西南,夏季弱且偏东北。在近45 a里,冬季及夏季风暴轴在整个对流层、尤其是对流层中上层具有整体一致的年际和年代际变化特征。在各个高度层上冬季风暴轴于1985年前后一致性地发生了由弱至强的年代际跃变;夏季风暴轴发生年代际由弱至强跃变的时间在各个高度层上略有不同,对流层中高层的跃变时间与北太平洋大气海洋系统1970年代的跃变时间一致。在冬季风暴轴活动偏强年里,中纬度天气尺度瞬变扰动增强的同时,位置也有所北抬,反之亦然。夏季风暴轴活动偏强(弱)年则主要表现为瞬变扰动在气候平均位置上的增强(减弱)。

PRIMIARY ANALYSIS OF THE CLIMATIC CHARACTERISTICS AND VARIABILITY OF THE NORTH PACIFIC STORM TRACK

The climatic characteristics and temporal evolution of North Pacific storm track at different levels in different season are analyzed by using ECMWF reanalysis grid data(ERA-40).The results show that the North Pacific storm track is stronger in winter and locates southwestward.It is weaker in summer and locates northeastward.In recent 45 years,the storm track in the whole troposphere,especially at the mid and upper troposphere,has consistent interannual and decadal variability.The winter storm track at different levels goes through an abrupt change around 1985 from negative anomaly to positive anomaly.Meanwhile,the times of the abrupt change for summer storm track are different for different level.The time at mid and upper troposphere is the same as the North Pacific air-sea system around 1970s.When the winter storm track activity is stronger,the midlatitude transient eddy activity is stronger and shifts northward,vice versa.When the summer storm track is stronger,transient eddy activity is stronger at its climatologically location.