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利用1979-2015年的NCEP/NCAR逐日再分析资料,分析了2009年冬季北半球平流层强爆发性增温事件(Stratospheric Sudden Worming,SSW)爆发期间的环流演变、动力特征以及增温事件爆发前对流层的前期信号.结果表明,平流层极夜急流于1月中旬开始快速减弱,同时,平流层极区温度快速上升,10 hPa极夜急流核心纬度带(60°N-70°N)纬向平均纬向风于1月24日转变为东风,标志着此次强SSW的爆发.对行星波活动异常的诊断表明,从增温事件爆发前10天开始,中高纬度10 hPa平流层2波分量快速增强,同时1波分量出现减少;Eliassen-Palm(EP)通量2波分量在SSW爆发前5天达到最强,表明此次SSW是典型的2波主导的极涡分裂型增温事件.此次强事件引起2009年冬季平均2波EP通量异常,此异常几乎是37年来最强的.对对流层500 hPa环流的分析表明,增温事件爆发前,位于东北太平洋-北美大陆西部的正位势高度异常与气候态定常波的阿拉斯加高压脊呈同位相叠加,从而有效加强了对流层行星波2波向平流层中高纬地区的传播,成为指示此次增温事件爆发的最强的对流层前期信号.“,”Based on 1979-2015 NECP/NCAR daily reanalysis data,this paper analyzed the evolution of circulation and the dynamical characteristics during the major Stratospheric Sudden Warming (SSW) in the winter of 2009,and revealed the precursory signal in troposphere before the occurrence of this SSW.The results showed that the stratospheric polar night jet quickly weakened in mid-January,meanwhile the polar stratospheric temperature rapidly increased.On 24 January,the 10 hPa zonal mean zonal wind averaged over 60°N-70°N reversed from westerly to easterly wind,indicating the onset of this major SSW.The easterly wind lasted until the end of February.By diagnosing planetary wave anomalies,it is found that the extratropical planetary wavenumber 2 component of geopotential height anomalies on 10 hPa rapidly increased from 10 days before the SSW onset.But the planetary wavenumber 1 component reduced in the corresponding period.The magnitude of the increase of planetary wavenumber 2 overwhelms the decrease of the planetary wavenumber 1.The vertical component of Eliassen-Palm (EP) flux anomalies by planetary wavenumber 2 reached the maximum value 5 days before the SSW onset.All these indicate that this SSW is a typical vortex splitting event driven by planetary wavenumber 2.This major SSW caused the strongest planetary wavenumber 2 EP flux anomalies in the winter of 2009 during the period 1979-2015.Further analyses on geopotential height anomalies on 500 hPa showed that the positive anomalies that located in the northeastern Pacific and western North America were highly in phase with the Alaska ridge of the climatological stationary waves before SSW onset.This distribution strongly enhanced the propagation of planetary wavenumber 2 from extratropical troposphere to stratosphere and thus acted as the strongest tropospheric precursory signal for the occurrence of this SSW.It is noted that although there are some other anomalous height centers that interfere with climatological stationary waves,they do not have significantly positive impacts on the SSW occurrence.For example,the negative height center that locates in the north Atlantic and eastern North America is in phase with the climatological trough over eastern North America and out of phase with the climatological ridge over Western Europe.It enhances the planetary wavenumber 2 but weakens planetary wavenumber 1 simultaneously.The net effect of this anomalous center on the stratospheric planetary wave activities is less obvious than that of the positive anomalies that locate in the northeastern Pacific and western North America.