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Journal Articles Journal of marine research Year : 2015

Distinguishing turbulent overturns in high-sampling-rate moored thermistor string observations

Abstract

Turbulent overturns are distinguished from salinity-compensated intrusions in high-resolution moored thermistor string observations. The buoyancy frequency N is used to make the time dimensionless, "t*." This results in a primary, visual means to easily compare the duration of overturns with N, the natural frequency that separates internal waves from turbulent overturns. As a secondary means, the shapes of overturns are investigated. Above various sloping topography between 500 and 1,000 m water depth where the buoyancy period varies between ∼1,300 and 2,600 s, vertical overturns of ∼40 m last Δt* =0.2–0.4. This corresponds with the timescale of growth of model-stratified turbulence in the wake of a grid. Smaller-scale, weaker-turbulent, shear-induced Kelvin-Helmholtz overturns of ∼5 m are observed to last approximately Δt* = 0.03, whereas the passage of their train of multiple consecutive overturns lasts up to approximately Δt* = 0.95. Although the shape of overturns can distinguish salinity-compensated intrusions from turbulent overturns, the present observations from internal wave breaking above sloping topography show complex results of mixed features.
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Dates and versions

hal-01230894 , version 1 (16-09-2016)

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Hans van Haren, Louis Gostiaux. Distinguishing turbulent overturns in high-sampling-rate moored thermistor string observations. Journal of marine research, 2015, 73 (1), ⟨10.1357/002224015815782661⟩. ⟨hal-01230894⟩
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