| 摘要: |
| 采用TOPEX/POSEIDON(T/P)卫星高度计1993年1月—2000年12月海面高度数据, 研究包含了整个南极绕极流流系(40°—60°S)的海面高度低频变化。首先采用EOF分解方法获取南大洋时空分布的主要模态, 前3个EOF模态分别占总方差的24.8%、13.8%和10.7%。然后采用EMD方法分别分析了各个EOF模态的时间系数曲线的组成成分, 对南极绕极流海域的各种时间尺度变化给出了清晰的描述, 对于不同尺度变化所占的比例得到了定量的结果。研究结果明, EOF的各个模态不仅在形态上存在差异, 而且具有相互独立的物理背景。EOF的第一模态主要体现了以太阳辐射冬夏差异形成的年周期变化, 另一个显著的特征就是南极绕极流从1993—2000年海面的整体上升趋势。EOF的第二模态体现了陆地地形对南极绕极流的约束作用, 同时也显示了ENSO过程对南极绕极流, 特别是对南太平洋的海面高度变化的影响。EOF的第三模态则体现了南极绕极流对南大洋表面风场东西方向不均匀变化的响应。同时, 本文的研究也证明了EOF与EMD方法联合使用对揭示大范围时空变化有重要的实际意义。
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| 关键词: 南极绕极流, Topex/Poseidon卫星高度计, 经验正交函数, 经验模态分解 |
| DOI：10.11693/hyhz200303004004 |
| 分类号: |
| 基金项目:中国科学院知识创新项目,KZCX2-202号;国家“十五”社会公益研究专项,2001DIA50040号;国家重点基金项目,49634140号 |
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| LOW-FREQUENCY VARIABILITY OF THE ANTARCTIC CIRCUMPOLAR CURRENT SEA LEVEL DETECTED FROM TOPEX/POSEIDON SATELLITE ALTIMETER DATA |
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ZHOU QIN1, ZHAO Jin-Ping2, HE Yi-Jun1
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1.Institute of Oceanology, The Chinese Academy of Science;2.First Institute of Oceanography, state Oceanic Administration
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| Abstract: |
| The sea surface variability of Antarctic Circumpolar Current (ACC) is investigated from 8 years of merged Topex/Poseidon data (January 1993 to December 2000). The study area is a torus from 40°S to 60°S and covers most of the mean axis of ACC.The spatial and temporal variabilities of sea level are discussed through empirical orthogonal function (EOF) analysis. The first three EOFs account for 24.8%, 13.8%, 10.2% of the total variance, respectively. Because of the complexity of the amplitude time series, the physical interpretation of each mode in conventional EOF analysis is primarily qualitative, even of the lower modes. In this study, empirical mode decomposition (EMD) method is introduced to decompose time coefficients of the modes for interpreting them intensively and quantitatively. The first EOF describes variability over the annual time scale and arising trend of sea level from 1993 to 2000. The heat variability of the sun is responsible for the former. The second EOF not only describes the influences of the land of three continents to the north on the sea surface height variability, but also shows that the ENSO has a notable influence on ACC, especially in the south Pacific sector. The third EOF indicates sea surface height of ACC in response to the wind stress field variability, which is not zonally symmetric. The combination of EOF and EMD is an effective method in analyzing large-scale spatial and temporal variabilities.
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| Key words: Antarctic Circumpolar Current, Topex/Poseidon altimeter, Empirical orthogonal function, Empirical mode decomposition |
