an-empirical-investigation-of-nonlinear-energy-transfer-from-the-m2-internal-tide-to-diurnal-wave

Poster #1344 schou@hawaii.edu Presenting 2/24 (4-5 pm) An Empirical Investigation of Nonlinear Energy Transfer from the M2 Internal Tide to Diurnal Wave Motions in the Kauai Channel, Hawaii Sherry H CHOU, Douglas S LUTHER, Martin D GUILES, Glenn S CARTER, Thomas DECLOEDT Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA Observations: Long records of current profiles from the Hawaii Ocean Mixing Experiment Key Points: ● ● ● Strong semi-diurnal and diurnal internal tide beams are observed in the Kauai Channel Energy at M2 subharmonic (M2/2) is weak at all depths, including within M2 beam Bispectra can falsely indicate nonlinear interactions if diurnal tides are present Resonance conditions for triad of waves with wave numbers kj and frequencies ωj: (HOME) A2 and C2 moorings (Fig 3) show clear internal tide signals (Fig 4) at the semidiurnal frequency, modulated by a strong spring-neap cycle Possible PSI wave triad at 22˚N k1 + k2 = k3 ω1 + ω2 = ω3 Table Frequencies of interest are shown in the first row and column, in cycles per day (cpd); differences shown in matrix Nearest Discrete Fourier Transform (DFT) harmonics for record length T = 163.5 days shown for comparison (bottom rows).1 Fig Wave number diagram of a Parametric Subharmonic Instability (PSI) wave triad.1 Fig Mode-1 M2 internal tide at A2 (see Fig 3) could form PSI triad with secondary waves of vertical wavelengths ~50 m, separated in freq by