Distinguishing turbulent overturns in high-sampling-rate moored thermistor string observations
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.
van Haren, Hans, and Louis Gostiaux. 2015. "Distinguishing turbulent overturns in high-sampling-rate moored thermistor string observations." Journal of Marine Research 73, (1). https://elischolar.library.yale.edu/journal_of_marine_research/402