北半球环状模波流相互作用动力学研究进展

Advances on Wave-Flow Interaction Dynamics of NAM

总结了国内外学者对于北半球环状模(NAM:Northern Hemisphere Annular Mode)及其活动中心形成原因的研究成果。主要从NAM的天气、气候影响,波流相互作用原理对NAM形成的解释,NAM在北太平洋、北大西洋和北极3个区域活动中心的天气尺度波和行星尺度波活动等方面论述。NAM在对流层的变化与天气尺度波有关,北太平洋和北大西洋两个活动中心是天气尺度波活跃的区域,其峰值区表现为风暴轴,其中北大西洋天气尺度波破碎过程会使得NAM指数急剧变化。NAM在平流层的变化和准定常行星波关系密切,冬季准定常行星波会上传并与高纬平流层纬向流发生相互作用,从而引起北极极涡发生改变。准定常行星波将NAM 3个活动中心有机联系起来:对流层准定常行星波的纬向传播会影响北太平洋风暴轴的位置,而风暴轴的变化会影响下游北大西洋波破碎过程,同时准定常行星波的上传可以影响极涡活动。

The progresses in the studies in the recent years of NAM/AO （Northern Hemisphere Anuular Mode / Arctic Oscillation） are reviewed, with the emphases on the influences of the NAM/AO on weather and climate, the physical mechanisms of NAM/AO,the waveflow interaction theory, and the baroclinic Rossby wave and quasistationary planetary wave activities on the NAM/AO’s three regional activity centers. During recent years, many studies show that tropospheric fluctuations of NAM/AO are associated with baroclinic waves, while fluctuations are associated with the quasistationary planetary waves in the stratosphere. It is found that the regions where baroclinic wave activities are frequent are the Pacific and Atlantic in the Northern Hemisphere, and the peak value areas are manifested as storm tracks. Besides, the wave breaking is the trigger of NAM/AO events in North Atlantic. On the other hand, the stratospheric zonal winds modify the upwardpropagation of the troposphereoriginated planetary waves, and then these waves refract, reflect and break, which thereby create fluctuations in the strength of the polar vortex in winter. The planetary waves link the NAM/AO’s three regional activity centers： the horizontal propagation and dispersion of quasistationary waves are crucial for the Pacific storm tracks, and the latitudinal position of the Pacific storm track plays an important role for determining the phase of NAO; the propagation of quasistationary planetary waves into the stratosphere over high latitudes can alter the intensity of the polar vortex.