El Nino的周期变化和空间特征——兼应用PC和CPC分析太平洋海温距平场

本文联合利用实主成分(以下简称PC)分析和复主成分(以下简称CPC)分析,探讨太平洋SST演变的时空特征.结果表明:这两种分析方法得到的第一个主成分都展示El Nino随时间周期性变化,在PC中表现为峰谷的变化,在CPC中表现为振幅和位相的变化;相应的荷载向量主要反映El Nino和La Nina事件时期空间分布特征,大振幅区域位于主要冷暖洋流活动中心.第一个复荷载向量可以认为在驻波上附加一个南北向传播的行波.第二个荷载向量为一驻波,第三个复荷载向量看上去像一个东西向传播的行波,后两个特征型各自强调不同El Nino和La Nina时期的空间特征.驻波峰、谷区域之间呈现反相关关系;这里虽然没有研究波群和群速度,但就行波而言,也初步看出能量传播的路径.与复荷载向量对应的实荷载向量仅显示驻波特征.

Combined PC and CPC Analysis of SST Anomalies over Pacific Ocean in Connection with E1 Ni?o Recurrence Periods

Combined application of principal component (henceforth PC) and complex principal component (henceforth CPC) analysis to the study of temporal and spatial features of sea surface temperature (SST) of the Pacific Ocean gave the following results. The first eigenmode of both PC and CPC appears very well correlated to El-Nino and La-Nina time cycle, and its space distribution shows the peculiarity of these events that their largest amplitudes in areas which are located near the active centres of the main cold and warm ocean currents. This property appears as a standing wave on which a travelling wave is superimposed.The second eigenmode exhibits a space distribution which looks like a standing wave, while the third one seems to be a travelling wave for CPC and a standing wave for PC. PC and CPC of these last two eigenmodes appear correlated to different El-Nino and La-Nina occurrence periods, so they seem to indicate different distinctive features of various El-Nino and La-Nina years.The two travelling waves revealed by this analysis show different propagation directions; the first one moves south-northward, while the second one east-westward.The above results can also be used to get a first sight estimate of energy propagation paths without calculating the wave group velocities.