冬季东北冷涡对北太平洋风暴轴的可能影响

Possible influence of the northeast cold vortex on North Pacific storm track in winter

利用NCEP/NCAR逐日再分析资料及由吉林省气象局科研所提供的东北冷涡日历表,以1951/1952—2008/2009年58 a冬季为代表,分析了东北冷涡对北太平洋风暴轴产生的影响及其可能原因。结果表明:1)冬季东北冷涡发生天数变化与北太平洋风暴轴强弱变化呈显著的负相关关系,即当东北冷涡发生天数偏多(偏少)时,北太平洋风暴轴强度减弱(增强)。2)通过Morlet小波交叉谱分析发现,冬季东北冷涡发生天数的年际变化与北太平风暴轴强度变化存在准3 a尺度上的相关关系。3)在冬季,当东北冷涡发生天数偏多时,从东亚到西北太平洋沿岸低层温度降低,低层冷空气位于副热带急流和北太平洋风暴轴上游,且经向上处于两者之间,加之冷平流的作用,给副热带急流与北太平洋风暴轴活动区域带来了正好相反的局地斜压性的改变:副热带急流区域斜压性增加,变得强而窄,位置南压;而北太平洋风暴轴区域斜压性减小,同时由于西北太平洋区域低层温度降低,使得有利于涡动形成的波源效应减弱,风暴轴强度减弱。当东北冷涡发生天数偏少时,则反之。

Based on NCEP/NCAR daily reanalysis data and the northeast cold vortex（NECV） calendar from Meteorological Research Institute of Jilin province, this paper analyzes the influence of NECV on North Pacific storm track in winter of 1951/1952--2008/2009.Results show that： 1 ）There is a significantly negative relationship between the change in days of NECV and the intensity of North Pacific storm track in winter,i.e. ,the more（less） days of NECV appearance, the weaker（stronger） the storm track over North Pacific will be. 2 ）The wavelet cross spectrum analysis shows that the above relationship is most prominent on the quasi-three-year period.3）In the winter of more NECV years,the low level temperature is falling from East Asia to North Pacific, and the major lower level cooling is located in the upper-stream of both subtropical jet and storm track, and between them latitudinally, which may induce a reverse effect on the jet and track, i. e., a more southward, stronger and narrower jet because of the enhanced baroclinicity there, but a weaker storm track since the reduced baroclinicity and the lower level cooling in northwestern Pacific may weaken the wave seeding responsible for the eddy generation from East Asia to North Pacific;and vice versa.