Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons

CHEN Shengli; HU Jianyu; POLTON Jeff A.

doi:10.1007/s13131-015-0594-y

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Article Navigation > Acta Oceanologica Sinica > 2015 > 34(1): 38-43

CHEN Shengli, HU Jianyu, POLTON Jeff A.. Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons[J]. Acta Oceanologica Sinica, 2015, 34(1): 38-43. doi: 10.1007/s13131-015-0594-y

Citation:

CHEN Shengli, HU Jianyu, POLTON Jeff A.. Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons[J]. Acta Oceanologica Sinica, 2015, 34(1): 38-43. doi: 10.1007/s13131-015-0594-y

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Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons

doi: 10.1007/s13131-015-0594-y

1.
State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen 361102, China;National Oceanography Centre, Liverpool L3 5dA, UK
2.
State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen 361102, China
3.
National Oceanography Centre, Liverpool L3 5dA, UK

Received Date: 2014-04-08
Rev Recd Date: 2014-06-13

Abstract

Abstract

Features of near-inertial motions on the shelf (60 m deep) of the northern South China Sea were observed under the passage of two typhoons during the summer of 2009. There are two peaks in spectra at both sub-inertial and super-inertial frequencies. The super-inertial energy maximizes near the surface, while the sub-inertial energy maximizes at a deeper layer of 15 m. The sub-inertial shift of frequency is induced by the negative background vorticity. The super-inertial shift is probably attributed to the near-inertial wave propagating from higher latitudes. The near-inertial currents exhibit a two-layer pattern being separated at mid-depth (25-30 m), with the phase in the upper layer being nearly opposite to that in the lower layer. The vertical propagation of phase implies that the near-inertial energy is not dominantly downward. The upward flux of the near-inertial energy is more evident at the surface layer (<17 m). There exist two boundaries at 17 and 40 m, where the near-inertial energy is reflected upward and downward. The near-inertial motion is intermittent and can reach a peak of as much as 30 cm/s. The passage of Typhoon Nangka generates an intensive near-inertial event, but Typhoon Linfa does not. This difference is attributed to the relative mooring locations, which is on the right hand side of Nangka's path (leading to a wind pattern rotating clockwise with time) and is on the left hand side of Linfa's path (leading to a wind pattern rotating anti-clockwise with time).
- near-inertial motions,
- typhoon,
- South China Sea

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