Cite this paper:
Shengming YUAN, Xiaomei YAN, Linlin ZHANG, Bing YANG, Chongguang PANG, Dunxin HU. The near-inertial waves observed east of the Philippines[J]. Journal of Oceanology and Limnology, 2022, 40(5): 1889-1908

The near-inertial waves observed east of the Philippines

Shengming YUAN1,4, Xiaomei YAN1,2,3, Linlin ZHANG1,2,3, Bing YANG1,2,3, Chongguang PANG1,2,3, Dunxin HU1,2,3
1 Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;
2 Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China;
3 Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China;
4 College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China
Based on mooring observations from Aug. 1, 2016 to Dec. 14, 2017, the characteristics and underlying mechanisms of near-inertial waves (NIWs) observed east of the Philippines were studied. Three strong NIW events were investigated in detail. The NIWs in Event Ⅰ were induced by typhoon Lan and had the strongest magnitudes of 0.35 m/s. The maximum near-inertial kinetic energy (NIKE) was shown at the ocean surface. The NIW in Event Ⅱ was stimulated by a moderate cyclonic wind with the extreme NIKE located at about 110-m depth. The existence of a cyclonic eddy during Events Ⅰ and Ⅱ led to a blue shift of near-inertial frequencies. For Event Ⅲ, the surface near-inertial signals were also induced by local weak wind, whereas the real generation mechanisms for the subsurface NIWs remain unclear. In particular, during Event Ⅲ, there was a nonlinear wave-wave interaction between NIWs and semidiurnal (D2) tides, which further induced strong D2±f waves. Overall, the NIWs in the three events exhibited distinct vertical structures. The NIWs in Events Ⅰ and Ⅱ were dominated by lower modes with elevated NIKE well confined to the upper 250 m and 270 m, respectively. In contrast, the NIW Event Ⅲ was dominated by higher modes and the NIWs penetrated downward beyond 360 m. Such deep penetration of NIWs could be attributed to the weak wind stress curl and positive sea level anomalies associated with an anticyclonic eddy. In addition, the three NIW events had e-folding timescales of less than 7 days.
Key words:    near-inertial wave (NIW)    generation mechanism    dynamic characteristic   
Received: 2021-06-10   Revised: 2021-08-18
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