Journal of Tropical Oceanography ›› 2018, Vol. 37 ›› Issue (6): 16-25.doi: 10.11978/2018014CSTR: 32234.14.2018014

Special Issue: 南海专题

• Marine Hydrography • Previous Articles     Next Articles

A study of near-inertial oscillations in the northern South China Sea based on in-situ observations during the passage of Typhoon Kalmaegi

Yandan HUANG1,2, Jiexin XU1, Junliang LIU1, Zhiwu CHEN1, Shuqun CAI1()   

  1. 1. State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China;
  • Received:2018-01-25 Online:2018-11-20 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)

Abstract:

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.

Key words: near-inertial oscillations, wave-wave interaction, typhoon, the northern South China Sea

CLC Number: 

  • P731.24