(Abbreviated TKE. ) The mean kinetic energy per unit mass associated with eddies in turbulent flow. A budget equation for TKE can be formed from the Navier–Stokes equations for incompressible fluid flow through Reynolds decomposition and Reynolds averaging. For most meteorological applications it is assumed that buoyancy effects are in the z direction only, that the mean vertical velocity is zero (hydrostatic scaling), and that molecular diffusion is neglected. See Also hydrostatic balance, isotropic turbulence, local isotropy, Reynolds number, Reynolds stresses, turbulence length scales, turbulence spectrum, viscous fluid.