Latitudinal Variation and Nonlinear Behavior of Internal Tides in the East China Sea

Author(s):  
Weidong Wang ◽  
Robin Robertson

<p>We present four sets of concurrent ADCP data obtained from the East China Sea shelf, and it suggests that near-inertial waves induced by parametric subharmonic instability (PSI) associated with harmonic transfer beyond diurnal critical latitude (O<sub>1</sub>:27.6°, K<sub>1</sub>:30°). Two type different nonlinear behavior (harmonic transfer and subharmonic transfer) occur varying with the latitude on different location. The velocity data indicated a transfer of diurnal internal tidal energy poleward of the diurnal critical latitude. Kinetic energy and shear spectra analysis at these moorings reveals that the prominent peaks enhance and appear at not only at the even order of diurnal tide such as semidiurnal band, 4cpd, 6cpd and even 8cpd, but also some unfamiliar odd harmonics 3cpd and 5cpd. Furthermore, additional energy is converted to higher mode locally through continuum internal wave spectrum. Besides the harmonic transfer, on the critical latitude for D<sub>2</sub>/2 wave(28.9°), D<sub>1</sub> wave is extracted from a D<sub>2</sub> tidal driven model output current. PSI conversion of semidiurnal internal tidal energy was confirmed by spectra analysis and bi-spectra, because of the distinguish of M<sub>2</sub>/2 separated from the diurnal tidal (O<sub>1</sub>, K<sub>1</sub>).</p>

2006 ◽  
Vol 33 (5) ◽  
Author(s):  
Jae-Hun Park ◽  
Magdalena Andres ◽  
Paul J. Martin ◽  
Mark Wimbush ◽  
D. Randolph Watts

2020 ◽  
Vol 50 (4) ◽  
pp. 907-920
Author(s):  
Wei Yang ◽  
Hao Wei ◽  
Liang Zhao

AbstractOn the basis of measurements from an observing mooring system, the observational evidence of parametric subharmonic instability (PSI) that transfers energy from semidiurnal internal tides (ITs) to the subharmonic waves at the East China Sea continental shelf slope is presented for the first time. Although the mooring station is very close to the energetic semidiurnal IT generation site, about 76% of the observed shear variance is contained in the near-inertial band, which is found to have comparable upward- and downward-propagating energy components. Bispectra and bicoherence estimates further confirm the occurrence of PSI transferring energy from the low-mode M2 ITs (vertical wavelength of ~1000 m) to high-mode subharmonic waves (vertical wavelength of ~200 m). The calculated energy transfer rate reveals an averaged net value of ~5 × 10−9 W kg−1. Strong temporal variation of is found that is not exactly in phase with the semidiurnal energy flux. After looking into the local vorticity fields, it is strongly suggested that the varying background relative vorticity associated with the evolving Kuroshio has modified the efficiency of PSI at the mooring location through changing the local effective inertial frequency.


2013 ◽  
Vol 71 (1) ◽  
pp. 151-185 ◽  
Author(s):  
Ren-Chieh Lien ◽  
Thomas B. Sanford ◽  
Sen Jan ◽  
Ming-Huei Chang ◽  
Barry B. Ma

Author(s):  
Huiping Xu ◽  
Changwei Xu ◽  
Rufu Qin ◽  
Yang Yu ◽  
Shangqin Luo ◽  
...  

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