Similarity of structure-function parameters in the stably stratified boundary layer

The structure-function parametersC _T ² andC _v ² of temperature and velocity, respectively, from the 1973 Minnesota experiments and from large-eddy and direct numerical simulations show a smooth transition from M–O similarity to the local scaling hypothesized by Nieuwstadt for the outer regions of the stable boundary layer. Under that hypothesis, turbulence statistics aloft depend on the local vertical fluxes of momentum and temperature, so these results suggest that remote-sensing measurements ofC _T ² andC _v ² could be used to infer vertical profiles of those fluxes. We argue that the sensitivity of the fluxes to unsteadiness, baroclinity, terrain slope, and breaking gravity waves precludes the universality of the vertical profiles of structure-function parameters in the stable PBL. We find that theC _T ² profile is particularly sensitive to these effects, which is consistent with observations that it varies considerably from case to case.