基于实测资料的南海北部台风“海鸥”致近惯性振荡研究
作者简介:黄妍丹(1992—), 女, 广东省汕头市人, 硕士研究生, 从事近惯性内波研究。
收稿日期: 2018-01-25
网络出版日期: 2018-12-24
基金资助
国家自然科学基金项目(41430964、41521005、41776005);中国科学院前沿科学重点研究计划(QYZDJ-SSW-DQC034)
A study of near-inertial oscillations in the northern South China Sea based on in-situ observations during the passage of Typhoon Kalmaegi
Received date: 2018-01-25
Online published: 2018-12-24
Supported by
Natural Science Foundation of China (41430964, 41521005, 41776005);Key Research Program of Frontier Sciences, Chinese Academy of Sciences (QYZDJ-SSW-DQC034)
Copyright
文章利用2014年9月南海东北部附近海域的A、B两个相距约20km的潜标数据, 分析了台风“海鸥”在南海东北部激发的近惯性振荡的垂向分布特征。结果表明, 台风过境在两站点激发了强烈的近惯性振荡, 其能量由海表向海洋内部传播; 近惯性能量在表层随着深度增加而增大, 最大值出现在次表层, 此后随着深度增加迅速衰减。但是两个观测站点的近惯性振荡垂向分布特征有较大的差别: A站点的近惯性振荡在不同深度上存在三个不同的垂向相速度, 而B站点的垂向相速度没有变化; 两站点的最大近惯性动能的大小及其所在深度不同, B站点比A站点的最大近惯性动能大15%左右。台风过后两个站点均出现由近惯性波f和半日内潮波D2非线性相互作用产生的次级波动fD2, 但其强度存在差异。台风后A站点fD2在不同深度上有不同的变化, f和D2相互作用较弱; 而B站点的fD2在整个近惯性振荡影响深度内都是增强, 其fD2和f频带的动能和流速在时空分布以及变化趋势上有较好的相关性。两站点的近惯性振荡垂向相速度以及次级波动fD2的不同可能是水体层结的差异和涡旋的影响所导致的。
黄妍丹 , 许洁馨 , 刘军亮 , 陈植武 , 蔡树群 . 基于实测资料的南海北部台风“海鸥”致近惯性振荡研究[J]. 热带海洋学报, 2018 , 37(6) : 16 -25 . DOI: 10.11978/2018014
In this study, the vertical characteristics of near-inertial oscillations (NIOs) induced by Typhoon Kalmaegi are analyzed by using data from two moorings about 20 km apart in the northeastern South China Sea in Sept. 2014. The results show that the energy of typhoon-induced NIOs, which propagates downward into the ocean interior, increases with depth in the upper layer and becomes maximum in the mid layer before dissipating with depth. However, we find that there is a large difference in vertical characteristics of typhoon-induced NIOs between the two moorings. The NIOs at mooring A had three different vertical phase velocities at different depths while the NIOs at mooring B showed invariable phase velocity. The value and depth of the maximum near-inertial kinetic energy (NIKE) are also different at the two moorings. The maximum NIKE was 15% greater at mooring B than at mooring A. After the passage of Kalmaegi, fD2 via nonlinear wave interaction between f and D2 occurred at the two moorings, except that the intensities of fD2 at the two moorings were different. At mooring A, fD2 changed with depth and its interaction between f and D2 was weak. The energy of fD2 at mooring B enhanced at the full depth, and the kinetic energy and velocities of fD2 and f had a good correlation for their time-space distributions and variations. The difference of vertical phase velocity of NIOs and fD2 at the two moorings may be caused by the effects of eddy and different stratifications.
Fig. 1 Locations of moorings A and B (+) and the track of Typhoon Kalmaegi (line with dots). |
Fig. 2 Continuous wavelet power spectra of u (a-c) and v (d-f) components of total observed currents at depths of 150 m (a, d), 200 m (b, e), and 250 m (c, f) at mooring A. |
Fig. 3 Same as |
Fig. 4 Wave number rotary spectra of the three main frequencies of baroclinic currents at moorings A (a-c) and B (d-f). Cm is the clockwise rotary spectrum, and Am is the anticlockwise rotary spectrum. |
Fig. 5 u in the upper 600 m observed at moorings A (a) and B (b). |
Fig. 6 Power spectra of u before (Sep. 5~14) and after (Sep. 15~24) Typhoon Kalmaegi at depths of (a) 150 m, (b) 200 m and (c) 250 m at mooring A. |
Fig. 7 Same as |
Fig. 8 Vertical distributions of amplitude of vertical nonlinear terms at moorings A (a) and B (b) before and after Typhoon Kalmaegi. |
Fig. 9 Vertical distributions of kinetic energy of f, D2 and fD2 before (the black line) and after (the red line) Typhoon Kalmaegi at moorings A (a-c) and B (d-f)图9 站点A (a—c)、B (d—f)台风前(黑色实线)和台风后(红色实线)f动能 (a、d), D2动能(b、e)和fD2动能 (c、f)垂向分布 |
Fig. 10 Distributions of the east-west components of currents at frequencies f (a, d), D2 (b, e) and fD2 (c, f) at moorings A (a-c) and B (d-f)图10 站点A(a—c)、B(d—f)的f频带(a、d), D2频带(b、e)和fD2频带(c、f)滤波的东西向流速分量分布 |
Fig. 11 Distribution of sea level anomaly on Sep. 22图11 9月22日海面高度异常值分布 |
The authors have declared that no competing interests exist.
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