Cospectral similarity in the atmospheric surface layer

Abstract There are two asymptotic cases where the four parameters which determine surface layer turbulence structure reduce to three. In the unstable limit, which we call local free convection, the surface stress is no longer important. In the stable limit z no longer enters; we propose the name ‘local z ‐less stratification’ for this state. In both cases explicit predictions result for various properties of the cospectra of stress and heat flux. Although the predictions are based on asymptotic arguments and therefore might be expected to hold only at large ∣ z / L ∣ values, data from the 1968 Kansas experiments show that most predictions are valid fairly close to neutral.