THE TURBULENT KINETIC-ENERGY BUDGET IN THE ATMOSPHERIC SURFACE-LAYER - A REVIEW AND AN EXPERIMENTAL REEXAMINATION IN THE FIELD

The one-dimensional equation for the turbulent kinetic energy budget in steady. horizontally-homogeneous flow near the ground is reviewed, and some of the many experimental evaluations of its stability-dependent terms obtained during the last twenty years are compared. Uncertainties attributable to instrument error and inadequate sites are discussed, and it is demonstrated that improved equipment makes it possible to evaluate contributions to the budget with comparatively simple experiments. A preliminary field study finds a von Karman constant of k = 0.387 +/- 0.016 and a wind shear function for the unstable surface layer phi(m) = (1 - 22.6z/L)-1/4; the form (1 - 15.1z/L)-1/3 fits equally well over the limited range of instability observed. Turbulence dissipation is found to be 15 to 20% too small to balance the production of energy by wind shear in the neutral surface layer, and this deficit appears to remain approximately constant relative to the total rate of energy production as instability increases to z/L = -0.12. Renormalized dissipation rates originally measured by others are shown to exhibit similar behavior beyond this narrow range. Combining these results with those of the present study suggests a dissipation function of the form phi(epsilon) = phi(m) - z/L + c in which c = -0.16 represents a near constant, net negative contribution made by the sum of the divergent transport terms.