Data from: A method of separating linear internal wave and vortical mode energies using shipboard ADCP velocity measurements

We present a method to quantify total, horizontal kinetic and available
potential energies of linear internal waves (IW) 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. 2014, 2017, 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. IW total energy spectrum is EIW = 2Kdiv . VM
total energy is EVM=1/Bu[(1+Bu)Krot-Kdiv], where Bu is Burger number with
N and f buoyancy and inertial frequencies, kh horizontal wavenumber
magnitude and kz 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. EVM derived by this new method agrees with
results computed using the Bühler et al. (2014, 2017) method 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=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 (100m) – O (100km) and
vertical scales O (10m) – O (100m).