In this study, integral turbulent statistics obtained in the roughness sublayer over a Midwestern deciduous forest (canopy height ~ 22 m) are examined for deviations from the Monin-Obukhov similarity. Correlation- and structure functions are used to estimate integral turbulent time and length scales, and to identify periods of weak and non-stationary turbulence when eddy-covariance fluxes are unlikely to represent net ecosystem sinks or sources. In addition to the typical diurnal course, we examine the effects of seasonal changes of forest morphology (LAI). The influences of local landscape (small topography, lakes, forest heterogeneity) are inferred from the variations in turbulence characteristics from different upwind directions. The effects of commonly applied coordinate rotations on covariance and correlations of "vertical" velocity and scalars are also discussed.
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