Open AccessStimulated Imbalance and the Enhancement of Eddy Kinetic Energy Dissipation by Internal Waves
Author(s) -
Roy Barkan,
Kraig B. Winters,
James C. McWilliams
Publication year - 2017
Publication title -
journal of physical oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.706
H-Index - 143
eISSN - 1520-0485
pISSN - 0022-3670
DOI - 10.1175/jpo-d-16-0117.1
Subject(s) - mesoscale meteorology , dissipation , kinetic energy , energy cascade , mechanics , cascade , forcing (mathematics) , physics , wavenumber , internal wave , geology , atmospheric sciences , meteorology , turbulence , thermodynamics , classical mechanics , chemistry , optics , chromatography
The effects of internal waves (IWs), externally forced by high-frequency wind, on energy pathways are studied in submesoscale-resolving numerical simulations of an idealized wind-driven channel flow. Two processes are examined: the direct extraction of mesoscale energy by externally forced IWs followed by an IW forward energy cascade to dissipation and stimulated imbalance, a mechanism through which externally forced IWs trigger a forward mesoscale to submesoscale energy cascade to dissipation. This study finds that the frequency and wavenumber spectral slopes are shallower in solutions with high-frequency forcing compared to solutions without and that the volume-averaged interior kinetic energy dissipation rate increases tenfold. The ratio between the enhanced dissipation rate and the added high-frequency wind work is 1.3, demonstrating the significance of the IW-mediated forward cascades. Temporal-scale analysis of energy exchanges among low- (mesoscale), intermediate- (submesoscale), and high-frequency (IW) bands shows a corresponding increase in kinetic energy E k and available potential energy APE transfers from mesoscales to submesoscales (stimulated imbalance) and mesoscales to IWs (direct extraction). Two direct extraction routes are identified: a mesoscale to IW E k transfer and a mesoscale to IW APE transfer followed by an IW APE to IW E k conversion. Spatial-scale analysis of eddy–IW interaction in solutions with high-frequency forcing shows an equivalent increase in forward E k and APE transfers inside both anticyclones and cyclones.