A Method of Separating Linear Internal Wave and Vortical Mode Energies Using Shipboard ADCP Velocity Measurements.

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Title:	A Method of Separating Linear Internal Wave and Vortical Mode Energies Using Shipboard ADCP Velocity Measurements.
Authors:	VLADOIU, ANDA¹ avladoiu@apl.uw.edu, LIEN, REN-CHIEH¹
Source:	Journal of Atmospheric & Oceanic Technology. Jan2026, Vol. 43 Issue 1, p61-75. 15p.
Subjects:	Internal waves, Acoustic Doppler current profiler, Potential energy, Helmholtz equation, Kinetic energy, Rotational flow, Oceanography
Abstract:	We present a method to quantify total, horizontal kinetic and available potential energies of linear internal waves (IWs) and vortical mode (VM) using only two-dimensional (2D) (depth, along-track distance) measurements of horizontal velocity, such as those commonly taken by oceanic shipboard ADCP (SADCP). Previous IW and VM energy decomposition methods (Bühler et al., and their extensions) require both velocity and buoyancy measurements. Applying Helmholtz decomposition, 2D horizontal kinetic energy wavenumber (kx, kz) spectra are projected onto divergent Kdiv and rotational Krot components. IWtotal energy spectrum is EIW 5 2Kdiv. VM total energy is EVM 5 1/Bu[(1 1 Bu)Krot 2 Kdiv], where Bu 5 (N2k2 h)/(f 2k2z) is Burger number with N and f the buoyancy and inertial frequencies, kh the horizontal wavenumber magnitude, and kz the vertical wavenumber. IW and VM horizontal kinetic energy (K) and available potential energy (P) can be inferred from EVM and EIW as functions of Bu. The proposed method, derived directly from IW and VM theoretical polarization relations, is demonstrated using two sets of velocity and density data. The EVM derived by this new method agrees with results computed using the 2014 and 2017 Bühler et al. methods at Bu; O(1) and within a factor of; 2-3 elsewhere, confirming that IW and VM energy can be separated using only velocity data. At Bu, O(0.1), EVM is dominated by PVM, with KVM/PVM 5 Bu, and using K alone to extract EVM through the proposed method is challenging due to inherent uncertainty in spectral measurements. This method could be applied to global SADCP datasets to separate upper-ocean IW and VM energy contributions in different dynamical regions at horizontal scales O(100) m-O(100) km and vertical scales O(10)-O(100) m. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

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Abstract:	We present a method to quantify total, horizontal kinetic and available potential energies of linear internal waves (IWs) and vortical mode (VM) using only two-dimensional (2D) (depth, along-track distance) measurements of horizontal velocity, such as those commonly taken by oceanic shipboard ADCP (SADCP). Previous IW and VM energy decomposition methods (Bühler et al., and their extensions) require both velocity and buoyancy measurements. Applying Helmholtz decomposition, 2D horizontal kinetic energy wavenumber (kx, kz) spectra are projected onto divergent Kdiv and rotational Krot components. IWtotal energy spectrum is EIW 5 2Kdiv. VM total energy is EVM 5 1/Bu[(1 1 Bu)Krot 2 Kdiv], where Bu 5 (N2k2 h)/(f 2k2z) is Burger number with N and f the buoyancy and inertial frequencies, kh the horizontal wavenumber magnitude, and kz the vertical wavenumber. IW and VM horizontal kinetic energy (K) and available potential energy (P) can be inferred from EVM and EIW as functions of Bu. The proposed method, derived directly from IW and VM theoretical polarization relations, is demonstrated using two sets of velocity and density data. The EVM derived by this new method agrees with results computed using the 2014 and 2017 Bühler et al. methods at Bu; O(1) and within a factor of; 2-3 elsewhere, confirming that IW and VM energy can be separated using only velocity data. At Bu, O(0.1), EVM is dominated by PVM, with KVM/PVM 5 Bu, and using K alone to extract EVM through the proposed method is challenging due to inherent uncertainty in spectral measurements. This method could be applied to global SADCP datasets to separate upper-ocean IW and VM energy contributions in different dynamical regions at horizontal scales O(100) m-O(100) km and vertical scales O(10)-O(100) m. [ABSTRACT FROM AUTHOR]
ISSN:	07390572
DOI:	10.1175/JTECH-D-25-0076.1