南海的偶极子模式

Bipole mode in South China sea

为了了解南海的海平面变化规律,利用希尔伯特-黄变换(HHT)对南海卫星高度计资料进行了分析.对南海卫星高度计资料进行潮汐校正和空间插值得到时间序列数据,对这些时间序列数据进行HHT,得到了南海海平面高度变化的三维能量-频率-时间谱和海平面高度距平(SSA).结果表明,在南海有一个偶极子存在,它的两极分别位于海南岛西南侧和吕宋岛西侧.冬季海南岛西南的SSA为正值约10 cm,而在吕宋岛的西侧为负值约-10cm;夏季前者具有负的水位距平约-10 cm,而后者为正值约10 cm.春季和秋季为SSA季节变化的过渡季节,东西向SSA梯度很小.

To understand the sea surface height change rule of the South China sea, altimeter data in the South China sea were analyzed with the Hilbert-Huang transform（HHT）. Altimeter data were corrected with tidal model and was interpolated in spatial domain to obtain time series data. 3D energy-frequencytime spectrum and sea surface anomaly （SSA） were obtained by HHT from time series data. The results show that a dipole-model exists in the South China sea with 2 poles in south-west to Hainan island and west to Luzon island respectively. The SSA of the pole south-west to Hainan island is about 10 cm and that of west to Luzon island is about -10 cm in winter, while the former is about --10 cm and the later is about 10 cm in summer. Spring and autumn are transitional seasons of SSA seasonal changes. The transmeridional gradient of SSA is very low.