赤道太平洋温度、流场距平EOF分析及与厄尔尼诺的关系

The EOF analysis of temperature and zonal flow in the equatorial Pacific Ocean and the study of the El Nino forecasting

利用EOF分析方法,讨论了最近20a赤道太平洋次表层温度、纬向流距平与厄尔尼诺的关系.结果表明:赤道太平洋海温距平EOF分析第一、二主分量占总量的近80％,其中第一主分量类似于厄尔尼诺模态,第二主分量类似于暖池模态;后一模态存在着突变和渐变两种过程,其中由冷位相变暖位相过程为渐变过程,而暖位相变冷位相过程为突变过程.厄尔尼诺事件是赤道西太平洋暖池突变过程的结果.赤道太平洋纬向流距平EOF的第二主分量代表赤道西太平洋潜流和东太平洋南赤道流的变化,这个模态存在着半年左右的振荡和与厄尔尼诺同位相的年际振荡两种频率.另外,它还存在明显的年代际变化.赤道西太平洋潜流和东太平洋南赤道流减弱是产生厄尔尼诺的必要条件.统计回归分析表明,赤道太平洋海温距平和纬向流距平EOF的第二特征向量的时间系数对厄尔尼诺和拉尼娜均有一定的预报意义.

The data of temperature and zonal flow anomaly in the equatorial Pacific Ocean which are meaned in 5°N -5°S with 5-430 m from 1980 to 2001 are analyzed with EOF method. The relation between the EOF main components of the temperature and zonal flow anomaly and El Nino is discussed. It is found that EOF first and second components of the temperature take about 80% among total amount. There are two processes in the second component. One is slow process and the other is quick process. The process from warm to cold is quick and the process from cold to warm is slow. The quick process results in El Nino. The first mode means the variation of Nino3 temperature and the second mode means the variation of warm pool in the equatorial western Pacific Ocean. The EOF second component of the zonal flow means the variation of the undercurrent in the western Pacific Ocean and the sea surface current in the eastern Pacific Ocean. There are two processes in the EOF second component of the zonal flow. One which takes an half year is slow and the other which is simarlar to E1 Nino is quick. It is necessary for the undercurrent to strongen in the western Pacific Ocean and for the sea surface current to weaken in the eastern Pacific Ocean. E1 Nino can been forecasted using EOF second components of the temperature and zonal flow anomaly in advence 8 to 12 months to some extent.