| 摘要: |
| 通过对1985年1月1日–1986年12月31日沿赤道5个锚定浮标站表层流速资料的分析，发现在140°W与108°W之间表层流速v存在一周期约为20d的显著振荡。该振荡是由波长约2000km、以1.15–1.23m/s的波速向西传播的波动引起的。该波动被推断为第二斜压模态混合Rossby惯性重力波。带通滤波和低通滤波结果表明，以110°W测站为例,20d振荡流速构方根为21.8cm/s（纬向）和22.1cm/s（经向）；单一流速振幅的特征值为30–50cm/s，最大振幅可达70cm/s；u季节变化的均方根小于17cm/s，v无明显季节变化。年平均流速通常小于5cm/s。以上各统计量表明，20d周期波动引起的v振荡在赤道东太平洋表层流速变化中非常显著。 |
| 关键词: 20d振荡 表层流速 混合Rossby惯性重力波 斜压模态 赤道太平洋 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金资助项目，49576276号 |
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| ANALYSIS ON THE CHARACTERISTICS OF 20-DAY PERIOD CURRENT OSCILLATIONS IN THE UPPER CENTRAL AND EASTERN EQUATORIAL PACIFIC OCEAN |
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WANG Fan1, WU De-xing2
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1.Institute of Oceanology, The Chinese Academy of Sciences, Qingdao, 266071;2.Marine Environmental College, Ocean University of Qingdao, Qingdao, 266003
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| Abstract: |
| Data from satellites, islands and buoys showed that there existed waves with 15–45 day period and 600–1600km wave length in the upper layer in the central and eastern Pacific. In the present study 2 year (Jan. 1, 1985–Dec. 31, 1986) velocity data gathered from 5 buoys (165°E, 140°W, 124°W, 110°W, 108°W) on the equator in the central and eastern equatorial Pacific were used to examine characteristics of the surface current in both and frequency domains.
Variations of current velocity at 10m depth were characterized by a 20-day period oscillation which was much more significantly revealed in the meridional component of velocity and between 140°w and 108°w. The oscillating and propagating features of the oscillation were revealed from the cross spectra between time series of velocity at different locations, from which the oscillation was identified to result from a westward-propagating wave with about 2000km wave length and 1.15–1.23m/s wave speed and mainly composed of the second baroclinic made of the mixed Rossby-inertia gravity wave, as the dispersive relationship of the equatorial trapped wave suggested.
The 7-to 30-day band-pass filtered r.m.s. (root of mean square) of velocity at the 10m depth were about 20cm/s at 165°E, 140°W,124°W, 110°W, 108°W on the equator. For example, the r.m.s. of zonal and meridional velocities at 0°, 110°W were 21.8cm/s and 22.1cm/s, respectively. Values of the oscillation amplitude were usually 30–50cm/s with maximum of 70cm/s. The r.m.s. of zonal velocities after 6-month low-passing filtering were 8–17cm/s, and the annual mean less than 5cm/s at 140°W, 124°W, 110°W, 108°W on the equator, suggesting that the 20-day period oscillation was quite significant in comparison with the annual mean.
Obtaining energy from the shear instability of the background currents, the oscillation amplitude between 140°W and 124°W showed a tendency increasing in direction of the group speed and eastward. |
| Key words: 20-d period oscillation, Surface current velocity, Mixed Rossby-inertia gravity wave, Baroclinic mode, Equatorial Pacific Ocean |
