Near-surface ocean kinetic energy spectra and small-scale intermittency from ship-based ADCP data in the bay of Bengal

Sukhatme, J and Chaudhuri, D and Mackinnon, J and Shivaprasad, S and Sengupta, D (2020) Near-surface ocean kinetic energy spectra and small-scale intermittency from ship-based ADCP data in the bay of Bengal. In: Journal of Physical Oceanography, 50 (7). pp. 2037-2052.

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Abstract

Horizontal currents in the Bay of Bengal were measured on eight cruises covering a total of 8600 km using a 300-kHz acoustic Doppler current profiler (ADCP). The cruises are distributed over multiple seasons and regions of the Bay. Horizontal wavenumber spectra of these currents over depths of 12�54 m and wavelengths from 2 to 400 km were decomposed into rotational and divergent components assuming isotropy. An average of across-and along-track spectra over all cruises shows that the spectral slope of horizontal kinetic energy for wavelengths of 10�80-km scales with an exponent of-1.7 ± 0.05, which transitions to a steeper slope for wavelengths above 80 km. The rotational component is significantly larger than the divergent component at scales greater than 80 km, while the ratio of the two is nearly constant with a mean of 1.16 ± 0.4 between 10 and 80 km. The measurements show a fair amount of variability and spectral levels vary between cruises by about a factor of 5 over 10�100 km. Velocity differences over 10�80 km show probability density functions and structure functions with stretched exponential behavior and anomalous scaling. Comparisons with the Garrett�Munk internal wave spectrum indicate that inertia�gravity waves account for only a modest fraction of the kinetic energy between 10 and 80 km. These constraints suggest that the near-surface flow in the Bay is primarily balanced and follows a forward enstrophy transfer quasigeostrophic regime for wavelengths greater than approximately 80 km, with a larger role for unbalanced rotating stratified turbulence and internal waves at smaller scales. © 2020 American Meteorological Society.

Item Type:	Journal Article
Publication:	Journal of Physical Oceanography
Publisher:	American Meteorological Society
Additional Information:	The copyright for this article belongs to American Meteorological Society.
Keywords:	Doppler effect; Kinetics; Probability density function, Acoustic doppler current profiler; Horizontal currents; Kinetic energy spectra; Rotational component; Small-scale intermittency; Stratified turbulence; Stretched exponential; Velocity difference, Kinetic energy, Acoustic Doppler Current Profiler; decomposition analysis; flow velocity; internal wave; kinetic energy; oceanic current; probability density function; vessel; wave spectrum; wavelength, Bay of Bengal; Indian Ocean
Department/Centre:	Division of Mechanical Sciences > Divecha Centre for Climate Change Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	15 Nov 2021 09:23
Last Modified:	15 Nov 2021 09:23
URI:	http://eprints.iisc.ac.in/id/eprint/66156

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