Observations of near-inertial waves induced by parametric subharmonic instability -- Journal of Oceanology and Limnology,2018,36(3):641-650

	Cite this paper:
	LI Bingtian, CAO Anzhou, LÜ Xianqing. Observations of near-inertial waves induced by parametric subharmonic instability[J]. Journal of Oceanology and Limnology, 2018, 36(3): 641-650

Observations of near-inertial waves induced by parametric subharmonic instability

LI Bingtian¹, CAO Anzhou^1,2, LÜ Xianqing¹

1 Physical Oceanography Laboratory/CIMST, Ocean University of China and Qingdao National Laboratory for Marine Science and Technology, Qingdao 266200, China;
2 Ocean College, Zhejiang University, Ministry of Education, Zhoushan 316021, China

Abstract:

Near-inertial waves (NIWs), which can be generated by wind or the parametric subharmonic instability (PSI) of internal tides, are common in the South China Sea (SCS). Moored current observations from the northern SCS have revealed that the PSI of semidiurnal (D₂) internal tides is another source of NIWs. The objective of this study was to examine the energy variance in the PSI of D₂ tides. The PSI of D₂ internal tides generated NIWs and waves with frequencies around the difference frequency of D₂ and f. The observed NIWs induced by PSI could be distinguished clearly from those elicited by typhoon Krosa. Shortly after Krosa entered the SCS, NIWs began to intensify on the surface and they propagated downward over subsequent days. The near-inertial currents were damped quickly and they became relatively weak before the waves were reinforced beneath the mixed layer when wind stress was relatively weak. Rotation spectra indicated an energy peak at exactly the difference frequency D₂-f of the NIWs and D₂, indicating nonlinear wave-wave interaction among D₂, f, and D₂-f. Depth-time maps of band-pass filtered velocities of D₂-f showed the waves amplified when the NIWs were reinforced, and they intensified at depths with strong D₂ tides. The energies of the NIWs and D₂-f had high correlation with the D₂ tides. The PSI transferred energy of low-mode D₂ internal tides to high-mode NIWs and D₂-f waves. For the entire observational period, PSI reinforcement was observed only when mesoscale eddies emerged and when D₂ was in spring tide, revealing a close connection between mesoscale eddies and NIWs. Mesoscale eddies could increase the energy in the f-band by enhancing the PSI of D₂ internal tides. Thus, this represents another mechanism linking the energy of mesoscale eddies to that of NIWs.

Key words: near inertial waves (NIWs)|parametric subharmonic instability (PSI)|South China Sea (SCS)

Received: 2016-11-17 Revised:

Tools

PDF (3593 KB) Free

Print this page

Add to favorites

Email this article to others

Authors

Articles by LI Bingtian

Articles by CAO Anzhou

Articles by LÜ Xianqing

References:
Alford M H, Shcherbina A Y, Gregg M C. 2013. Observations of Near-Inertial Internal Gravity Waves Radiating from a Frontal Jet. Journal of Physical Oceanography, 43(6):1 225-1 239.
Alford M H. 2008. Observations of parametric subharmonic instability of the diurnal internal tide in the South China Sea. Geophysical Research Letters, 35(15):596-598.
Alford M, MacKinnon J, Zhao Z, Pinkel R, Klymak J, Peacock T. 2007. Internal waves across the Pacific. Geophysical Research Letters, 34(24).
Arbic B K, Polzin K L, Scott R B, Richman J G, Shriver J F. 2013. On Eddy Viscosity, Energy Cascades, and the Horizontal Resolution of Gridded Satellite Altimeter Products*. Journal of Physical Oceanography, 43(43):283-300.
Farmer D, Li Q, Park J H. 2009. Internal wave observations in the South China Sea:The role of rotation and non-linearity. Atmosphere-Ocean (Canadian Meteorological& Oceanographic Soc), 47(4):267-280.
Firing E, Lien R C, Muller P. 1997. Observations of strong inertial oscillations after the passage of Tropical Cyclone Ofa. Journal of Geophysical Research Atmospheres, 102(C2):3 317-3 322.
Garrett C. 2001. What is the ‘near-inertial’ band and why is it different from the rest of the internal wave spectrum? Journal of Physical Oceanography, 31(4):962-971.
Gayen B, Sarkar S. 2013. Degradation of an internal wave beam by parametric subharmonic instability in an upper ocean pycnocline. Journal of Geophysical Research Oceans, 118(9):4 689-4 698.
Guan S, Zhao W, Huthnance J, Tian J, Wang J. 2014. Observed upper ocean response to typhoon Megi (2010) in the northern South China Sea. Journal of Geophysical Research Atmospheres, 119(5):3 134-3 157.
Halle C, Pinkel R. 2003. Internal wave variability in the Beaufort Sea during the winter of 1993/1994. Journal of Geophysical Research Oceans, 108(C7):331-351.
Haren H V. 2005. Tidal and near-inertial peak variations around the diurnal critical latitude. Geophysical Research Letters, 32(23):113-133.
Hibiya T, Nagasawa M, Niwa Y. 2002. Nonlinear energy transfer within the oceanic internal wave spectrum at mid and high latitudes. Journal of Geophysical Research, 107(C11):28-1-28-8.
Huang X, Zhang Z, Zhang X, Qian H, Zhao W, Tian J. 2017.Impacts of a mesoscale eddy pair on internal solitary waves in the northern South China Sea revealed by mooring array observations, J. Phys. Oceanogr., https://doi.org/10.1175/JPO-D-16-0111.1.
Jan S, Lien R C, Ting C H. 2008. Numerical study of baroclinic tides in Luzon Strait. Journal of Oceanography, 64(5):789-802.
Korobov A S, Kevin G. 2008. Interharmonics in internal gravity waves generated by tide-topography interaction.Journal of Fluid Mechanics, 611(611):61-95.
Korobov A S, Lamb K G. 2008. Interharmonics in internal gravity waves generated by tide-topography interaction.Journal of Fluid Mechanics, 611(17):61-95.
Kunze E. 1985. Near-inertial wave propagation in geostrophic shear. Journal of Physical Oceanography, 15(5):544-565.
Liang X, Thurnherr A M. 2012. Eddy-modulated internal waves and mixing on a midocean ridge. Journal of Physical Oceanography, 42(7):1 242-1 248.
Mccomas C H, Bretherton F P. 2004. Resonant interaction of oceanic internal waves. Journal of Geophysical Research, 31(82):1 397-1 412.
McComas C H, Müller P. 1981. The dynamic balance of internal waves. Journal of Physical Oceanography, 11(11):970-986.
Price J F, Morzel J, Niiler P P. 2008. Warming of SST in the cool wake of a moving hurricane. Journal of Geophysical Research:Oceans, 113(C7).
Shay L K, Chang S W, Elsberry R L. 1990. Free surface effects on the near-inertial ocean current response to a hurricane. Journal of physical oceanography, 20(9):1 405-1 424.
Tian J, Yang Q, Zhao W. 2009:Enhanced diapycnal mixing in the South China Sea. J. Phys. Oceanogr., 39:3 191-3 203, https://doi.org/10.1175/2009JPO2899.1.
Webster F. 1968. Observations of inertial-period motions in the deep sea. Reviews of Geophysics, 6(4):447-472.
Wright C J, Scott R B, Furnival D, Ailliot P, Vermet F. 2013.Global observations of ocean-bottom subinertial current dissipation. J. Phys. Oceanogr., 43(2):402-417.
Xie X H, Chen G Y, Shang X D, Fang W D. 2008. Evolution of the semidiurnal (M2) internal tide on the continental slope of the northern South China Sea. Geophysical Research Letters, 35(13):344-349.
Xie X H, Shang X D, Chen G Y, Lu S. 2009. Variations of diurnal and inertial spectral peaks near the bi-diurnal critical latitude. Geophysical Research Letters, 36(2):349-363.
Xie X H, Shang X D, Haren H V, Chen G Y, Zhang Y Z. 2011. Observations of parametric subharmonic instabilityinduced near-inertial waves equatorward of the critical diurnal latitude. Geophysical Research Letters, 38(5):132-140.
Yang B, Hou Y, Hu P, Liu Z, Liu Y. 2015. Shallow ocean response to tropical cyclones observed on the continental shelf of the northwestern South China Sea. Journal of Geophysical Research:Oceans, 120(5):3 817-3 836.
Zhai X, Greatbatch R J, Zhao J. 2005. Enhanced vertical propagation of storm-induced near-inertial energy in an eddying ocean channel model. Geophysical Research Letters, 32(18):109-127.
Zhang Z, Tian J, Qiu B, Zhao W, Chang P, Wu D, Wan X. 2016.Observed 3D structure, generation, and dissipation of oceanic mesoscale eddies in the South China Sea. Scientific Reports, 6.
Zhang Z, Zhao W, Qiu B, Tian J. 2017. Anticyclonic eddy sheddings from Kuroshio loop and the accompanying cyclonic eddy in the northeastern South China Sea, J.Phys. Oceanogr., https://doi.org/10.1175/JPO-D-16-0185.1.
Zhang Z, Zhao W, Tian J, Liang X. 2013. A mesoscale eddy pair southwest of Taiwan and its influence on deep circulation. Journal of Geophysical Research:Oceans, 118(12):6 479-6 494.