Near-Surface Stress Profile and Conditional Averaging of Turbulence

Using the conditional average formulation, we suggest a new explanation for why the stress in the atmospheric surface layer is often observed to vary with height. In essence, because turbulence series are always correlated for small lags, the steady-state equations of motion with negligible viscous terms that traditionally require vertical fluxes to be constant with height accordingly now require the vertical fluxes to vary with height. This result has implications for interpreting and validating Monin-Obukhov similarity theory.