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. ORCID: 2015 Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons. Acta Oceanologica Sinica, 34 (1). 38-43.

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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).

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 0253-505X
Additional Keywords: near-inertial motions, typhoon, South China Sea
Date made live: 05 Feb 2015 11:29 +0 (UTC)

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