冬季北半球极涡强度对北太平洋风暴轴的影响

利用美国NCEP/NCAR再分析资料和中国国家气候中心北半球极涡强度指数资料,采用相关和合成分析等方法,初步分析了北半球极涡强度对北太平洋风暴轴的影响及其可能机制。研究发现,北半球极涡与北太平洋风暴轴之间有同步的强弱变化特征,在北半球极涡强度的高(低)值年,一般对应着风暴轴强度的增强(减弱),风暴轴区域扰动动能的加大(减弱),天气尺度涡动向极和向上的热量以及西风动量输送的显著增强(减弱)。进一步分析表明,极涡的异常变化可以通过改变欧亚大陆及其下游北太平洋上空的高度场,进而改变东亚西风急流的强度以及风暴轴上游的斜压性,从而对风暴轴产生影响。

Effects of Northern polar vortex intensity on North Pacific storm track during winter

Based on U.S.NCEP/NCAR reanalysis data and Northern polar vortex intensity data from China National Climate Center,with correlation analysis and composite analysis,the effect of Northern polar vortex intensity on North Pacific storm track and its possible physical mechanism are studied.Conclusions are drawn as follows:In the years when Northern polar vortex is stronger(weaker),North Pacific storm track is also stronger(weaker).The stronger(weaker) North Hemisphere polar vortex will enhance(decrease) storm track and disturbance kinetic energy in the storm track area.In the years when Northern polar vortex is stronger(weaker),the synoptic-scale disturbance meridional and vertical heat transports are stronger(weaker) than mean,and the synoptic-scale disturbance transport of westerly momentum is stronger(weaker) significantly.Further investigation shows that the anomalous changes of polar vortex give rise to change in the upper level geopotential heights over the Eurasian continent and its downstream Pacific ocean,then change the East Asia westerly jet and the baroclinicity in the upstream of the storm track,and finally the storm track.