热带太平洋上层洋流异常的复EOF分析-海洋预报

热带太平洋上层洋流异常的复EOF分析

单位：1. 中国人民解放军61741部队, 北京 100094;
2. 中国人民解放军东海舰队海洋水文气象中心, 浙江宁波 315122

分类号：P732.6

出版年·卷·期（页码）：2014·31·第二期（56-66）

摘要：

采用复EOF分析方法,对全年热带太平洋海域的上层洋流异常做了统计动力诊断,主要结论有:热带太平洋上层洋流异常复EOF分解第一、二模态的空间场均为赤道所俘获,并在赤道南北方向均呈迅速衰减的态势,其表现为赤道陷波的形式。第一、二模态时间系数为复数,其辐角均集中在两个状态,其模则表示了流场异常的大小。该时间系数均有年际变化和年代际变化,其年际变化的周期均与ENSO相同;在冬季,其年代际变化周期分别与北太平洋主要气候模态PDO和NPGO,以及热带外北太平洋流场异常复EOF分解前两模态的周期相同或相近,这反映了热带与中纬度各大气、海洋系统之间的相互耦合。由各模态流场异常可得相应的垂直运动异常,从而可估计SSTA的动力变化;第一模态在赤道东、西太平洋处呈现东西向的跷跷板变化;第二模态则在西太平洋赤道上以及其北侧的西太平洋暖池处,呈现南北向的跷跷板变化。第一模态的性质为海洋赤道Kelvin波的异常,可称之为ENSO的主要模态;第二模态的性质为海洋混合Rossby-重力惯性波的异常,可称之为ENSO的次要模态。

In this paper, the dynamic statistic diagnosis has been done to analyze the upper abnormal circulation of tropic Pacific Ocean by using CEOF analysis. The results are: the first and second spatial modes of the current anomalies are captured by equator, which are appearing to be the equatorial capture wave and decaying rapidly from equator to north and south polewards. The time coefficients of the first two modes are all complex numbers, their arguments concentrate on two equilibrium states and the two modes' numeric values decide the magnitude of the deviation of flow fields. There are obvious inter-annual and inter-decadal variations of both time coefficients. The period of their inter-annual variation is similar to that of ENSO. In winter, the period of inter-decadal variation is same or similar as PDO and NPGO respectively, and the periods of the first and second modes about complex EOF decomposition of the North Pacific circulation are also similar, which reflect the mutually coupling between atmosphere and ocean system in tropic and mid-latitude. The abnormal vertical movement can be calculated from the corresponding circulation anomalies of each modes, which can estimate the dynamic changes of SSTA. The first mode presents the east-west seesaw change in the eastern and western equatorial pacific; the second mode presents the south-north seesaw change in the western equatorial Pacific and the Western Pacific warm pool. The nature of the first mode is the equatorial Kelvin ocean wave anomalies, which can be referred to the main mode of ENSO; the nature of the second mode is the mixed Rossby-gravity inertia wave anomalies, which can be referred to the secondary mode of ENSO.

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