南海海面高度年际变化的S-EOF分析

Analysis of interannual variability of sea-surface height in the South China Sea

应用依赖于季节的经验正交函数(S-EOF)分析,探讨了最近15a南海海面高度随季节演变的年际变化。S-EOF分析得出南海海面高度异常各模态不同季节的空间结构以及时间演变过程,证实了季风强盛期冬季和夏季基本模态的结构,还分离出了季风转换期(春季和秋季)海面高度的分布格局。结果表明,南海海面高度随季节演变的年际变化与厄尔尼诺和拉尼娜事件密切相关。S-EOF1的结果表明,南海海面高度的变化具有明显而稳定的季节振荡,但在ENSO年海面高度的季节振荡相对减弱;S-EOF2模态显示了1998—2001年间冬季吕宋岛西侧存在一个较强的正异常,且能一直持续到春季;S-EOF3模态主要体现了南海西部一系列中尺度涡状结构的年际差异,包含1997/1998年厄尔尼诺对南海环流的影响。

Fifteen years of interannual variability of the sea-surface height in the South China Sea（SCS） was discussed through the Seasonal-reliant Empirical Orthogonal Function（S-EOF） analysis.The S-EOF analysis illustrates spatial patterns of different seasons and the same temporal variations of the surface circulation in the SCS,not only confirming the winter and summer patterns during monsoons but also presenting new patterns in spring and fall.The result shows that the interannual variability of the sea-surface height in the SCS was closely related to the El Ni？o and La Ni？a events.The S-EOF1 shows that the variability of the sea-surface height in the SCS had obvious seasonal oscillation,and this seasonal oscillation was almost steady and relatively weaker during ENSO years.The S-EOF2 shows that there existed a comparatively strong positive anom-aly west of the Luzon in the winters of 1998？2001,and it lasted until the spring.The S-EOF3 is mainly characterized by the interannual variability of a series of meso-scale eddies in the western SCS and the strong impact of 1997/1998 El Ni？o on the circulation in the SCS.