摘要:利用美国国家环境预报中心和能源部（NCEP/DOE）的逐日再分析资料（NCEP-DOE AMIP-Ⅱ），对2010年12月20日发生在北太平洋一次典型的反气旋式波破碎（AWB）事件进行研究，分析了波破碎过程中等熵位涡场的演变特征，揭示了波破碎过程中高频扰动以及低频信号的逐日演变特征，并对2010年冬季350 K等熵面上逐日高频位涡（PV）扰动和低频变化做经验正交函数（EOF）分析，得到了其主要模态，并从等熵位涡方程出发研究了波破碎过程中位涡高、低频变化的原因。研究表明，波破碎过程中高频低PV空气从北太平洋西部日本附近沿东北方向向对流层上层侵入，而来自阿拉斯加湾附近的高频高PV空气向对流层下层侵入。高频位涡场EOF分解得到的前两个模态共同描述了北太平洋中纬度地区自西向东移动的天气尺度波列；低频位涡场EOF分解的第一模态在北太平洋呈弧形波列结构。天气尺度波在传播过程中受到低频场的平流作用逐渐偏离其传播主要模态的位置，并发生破碎，同时高频流场对高频位涡的平流可以产生低频变化，使得低频变化的空间形态向其冬季主要模态转变。
关键词:Rossby波破碎/
等熵面/
位涡/
高频扰动/
低频变化
Abstract:Based on NCEP-DOE AMIP-Ⅱ (National Centers for Environmental Prediction, U.S. Department of Energy, Atmospheric Model Intercomparison Project Ⅱ) daily reanalysis data, a typical case of Anticyclonic Wave Breaking (AWB) that occurred on 20 December 2010 in the North Pacific region and the characteristics of Isentropic Potential Vorticity (IPV) during this process were studied. Daily high-frequency eddies and low-frequency variabilities were investigated. In addition, research was conducted on the modes of high-frequency eddies and low-frequency variabilities through Empirical Orthogonal Function (EOF) method on 350 K isentropic surface in the winter of 2010. Budget analysis of the IPV was employed to examine the low-frequency and high frequency PV anomalies associated with the primary modes of EOF. The results show that during the process of the Rossby wave breaking, low PV air parcels that emerged over the Northwest Pacific near Japan traveled to the upper troposphere, while high PV air parcels invaded lower troposphere. The first two leading modes of high-frequency PV depict a middle-latitude wave train that propagated from west to east over the North Pacific. The first leading mode of the low-frequency PV spread in the North Pacific as an arched wave train. The track of synoptic waves could be altered by the low-frequency variability, causing the waves to break eventually; meanwhile, the advection of high-frequency flows contributed to the conversion of the primary mode from high-frequency variability to low-frequency variability in the winter.
Key words:Rossby wave breaking/
Isentropic surface/
Potential vorticity/
High-frequency eddy/
Low-frequency variability
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