2009年冬季平流层爆发性增温期间行星波活动特征

利用2008年12月至2009年4月的MERRA再分析数据资料，对2009年1月下旬北半球高纬平流层发生的强增温事件以及与之相关的行星波活动进行了研究.谱分析发现，SSW发生前后极区平流层内准16天行星波活动显著.利用二维谐波拟合法分别拟合温度场准16天波4个波模（W1，W2，E1，E2）的振幅和相位，结果表明:背景西风减弱时四个波模的振幅均有不同程度的增大，且都在50°-80°N范围内的平流层中上层达到最大值；准16天W2波的增幅最大且辐合最强烈，其引起的背景流最大西风减速超过4m·-1·d-1，说明准16天W2波在该次增温事件中占主导地位；行星波传播与零风线移动关系密切，准16天W2波在中高纬地区垂直向上传播并近似呈现经向驻波结构，然后分别向极点和赤道两个方向传播，这表明中高纬地区可能是行星波的一个源区. 

Characteristics of Planetary Wave Activity during the Stratospheric Sudden Warming in the Winter of 2009

Based on MERRA reanalyzed data from December 2008 to April 2009,the major SSW event and the relevant Planetary Wave(PW) activities are investigated.Spectral analyses show that the stratosphere over Northern Hemispheric polar region is dominated by quasi-16-day PW during this SSW event.The corresponding amplitudes and phases of its four wave modes,i.e.W1,W2,E1,and E2,have been fitted by using the two-dimensional harmonic fitting method.The results show that all the modes display increasing amplitudes in varying degrees when the westerly wind weakens,and reach their peaks from 50°N to 80°N in the middle and upper stratosphere finally.Particularly,the W2 mode shows the largest increment and the strongest convergence among them,leading to the maximum westerly deceleration of background wind which is more than 4 m·s-1·d-1.The W2 mode of quasi-16-day PW exhibits the most important contribution to this SSW event.Furthermore,the results also demonstrates that the propagation of PWs is closely related to the movement of zero wind line.The W2 mode propagates vertically upward and shows longitudinally quasi-standing structure in mid-high latitudes,and then propagates to the pole and equator respectively.The midhigh latitudes are likely to be a source region of PWs.