基于中心轴线的北太平洋冬季风暴轴分类及其机理研究

Classification, Based on the Central Axis, of Storm Tracks in the North Pacific in the Winter Season, and the Possible Underlying Physical Mechanism

利用NCEP/NCAR逐日再分析资料研究了63年（1948~2010年）冬季北太平洋风暴轴的时空演变,提取风暴轴的中心轴线作为研究主体,以风暴轴的经向分布差异为重点,用模糊C均值聚类分析的方法将风暴轴分为平均型、偏北型和偏南型三类,并探讨了各类风暴轴对应的海气异常型及其物理机制。结果表明：（1）三类风暴轴分别显示了风暴轴经向差异的具体物理图像,对应着不同的涡旋移动发展路径,具有明确的天气学意义。通过EOF分解证明本文的分类反映了风暴轴的主要变化特征,物理意义清晰,具有一定的合理性和实用性。（2）三类风暴轴不仅经向差异明显,其北抬南压的纬向位置也存在显著差异,进一步表明该分类方法充分考虑了风暴轴空间分布的经向纬向差异,还揭示了风暴轴多中心的特点。（3）三类风暴轴对应的不同SST异常通过热力过程影响大气的温度场、风场和位势高度场,导致阿留申低压强度位置异常和水平风场异常,进而影响大气斜压性,决定风暴轴的空间分布,是形成不同类型风暴轴的重要原因。

The spatiotemporal evolution of storm tracks in the North Pacific in winter is investigated using NCEP/NCAR reanalysis data from December 1948 to February 2010 and the Fuzzy C-Means method. The storm tracks are divided into three patterns： The Common Pattern（TCP）, The Northern Pattern（TNP）, and The Southern Pattern（TSP）. The air–sea interaction and physical characteristics of the three patterns are also investigated. The results are summarized as follows：（1） The physical meanings of the three patterns are clear. They show distinct differences in storm track meridional location, corresponding to different propagating routes of synoptic-scale eddies.（2） The classification of storm tracks not only shows the meridional and zonal differences, but also exposes the characteristics of multiple centers.（3） The three patterns are related to different Sea Surface Temperature Anomalies（SSTAs）. The SSTAs affect the strength and location of the Aleutian low in the lower troposphere, and the associated wind anomalies. As a result, the baroclinicity of the atmosphere is changed. The difference in the baroclinicity changes therefore causes different storm track spatial patterns.