冬季北大西洋风暴轴的东西变化及其能量诊断

Zonal variations and its energy budget analysis of North Atlantic storm track in winter

利用NCEP/NCAR再分析资料,定义一个风暴轴经度指数,基于这个指数做合成分析,对冬季北大西洋风暴轴63 a(1948—2010年)的东西变化特征及其能量平衡差异进行了诊断。主要结论如下:(1)北大西洋风暴轴存在明显地东扩和西退。当风暴轴向东扩展时,天气尺度瞬变波可以向下游发展至乌拉尔山以东的亚洲上空;风暴轴西退时,天气尺度瞬变波活动范围向西收缩到15°W以西的大洋上空。(2)能量诊断表明,当风暴轴向东扩展时,涡动动能在高纬度的大西洋东部及西欧上空明显增强。在0°以西的区域,涡动动能的增强主要归因于能量斜压转换过程的增强;而在0°以东区域,涡动动能的增强可能与涡动非地转位势通量引起的"下游发展效应"增强有关。风暴轴向西收缩时,变化相反。

Based on NCEP/NCAR reanalysis data and a self-defined storm track longitude index （Ix） , a syn- thetic analysis was made to conduct an investigation on zonal variability of Atlantic storm track （AST） and its ener- gy budget difference during boreal winters of the past 63 years （1948-2010）. Results show that （ 1 ） the AST swings markedly in the east-west direction. When it expands eastward, the synoptic transient waves extend from At- lantic to Asia over the east of the Ural in the sky ; while it retreats westward, the synoptic transient waves draw back to the west of 15° W over the ocean. （2） The energy budget analysis shows that the remarkable increase of the eddy kinetic energy over eastern Atlantic and western Europe at high latitudes corresponds to the eastern enlargement of the storm track. The intensification of eddy kinetic energy in the west of 0° is largely attributed to the strengthening of barotropic conversion, while in the east of 0°, the ＂ downstream development effect＂ caused by the eddy ageostrophic geopotential fluxes may play the most crucial role. Vice versa while the AST retreats.