Mechanism |
Parameterizations |
BOUNDARY LAYER TURBULENCE
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Isotropic turbulence generated by wind stirring, bottom friction, negative buoyancy fluxes, inhibated by stable stratification, and destroyed by dissipation. This type of turbulence occurs in boundary layers (surface mixed layer and bottom layer). |
The eddy coefficient involves the product of :
- "k": the TKE (Turbulent Kinetic Energy).
- "L": a master length scale related to eddies' size.
- "S": a stability function which represents the effects of stratification & velocity shear.
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INTERNAL MIXING
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Internal Wave Breaking
Gravity waves moving along the interior pycnocline can grow to unstability. The breaking of waves generate mixing in the cross-isopycnal direction.
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Observations indicate that the intensity of mixing is directly related to the Brunt-Vaisalla frequency which measures the vertical gradient of density.
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Shear Instability
Shear instability occurs in the thermocline when the destabilizing effect of the vertical shear of velocity overcomes the stabilizing effect of the buoyancy gradient. |
The tendancy for unstability is measured by the Richardson number "Ri" which is the ratio of the Prandtl frequency "M" (measure of shear) and the Brunt Vaisalla frequency "N" (measure of stratification) and occurs when Ri overcomes a critical Richardson number "Ri_c".
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