Since LES provides values of the considered meteorological variables in every point in the simulation domain at every time step, it appears attractive to use LES output data for structure-function parameter calculations. Previous studies estimated structure-function parameters from LES of CBL flow fields using supplementary relations between these parameters and turbulence dissipation/destruction rates. In our study, structure functions are calculated directly from the simulated flow fields.

Calculated structure functions plotted versus separation distance exhibit a 2/3 power slope over an extended range of separations. It is for this range that structure-function parameter definition makes sense. The lower limit of the 2/3 slope range depends on simulation spatial resolution and the subfilter-scale model employed in LES. The behavior of structure-function parameters evaluated from LES in the lower portion of the CBL generally agrees with Monin-Obukhov similarity theory predictions. In the mixed portion of the layer, the temperature structure-function parameter nondimensionalized using mixed-layer scales is found to follow the -4/3 law. The magnitude of the proportionality coefficient is, however, smaller than its previous estimates in the literature. As in previous numerical and observational studies, the nondimensionalized mixed-layer structure-function parameter for humidity is strongly influenced by entrainment. For structure functions of horizontal velocity components, the ratio of transverse and longitudinal structure-function parameters is approximately 4/3. This ratio tends to be larger than 4/3 for structure functions of the vertical velocity component. Shear-induced anisotropy of turbulence structure in the CBL is investigated through comparison of structure functions calculated from sheared and idealized shear-free simulations.