Atmospheric turbulence represents a quintessential multiscale, intermittent dynamical system in which energy transfer occurs through complex cascade processes. In atmospheric surface layers (ASLs), these processes are complicated by ground roughness, giving rise to pronounced intermittency and coherent turbulence structures. This study investigates ASL turbulence, characterizes the multifractal features, and examines the coherent structures in intermittency. Wind tunnel experiments unveil how idealized, identical roughness elements affect aerodynamic resistance and transport. Moreover, field measurements are collected by an eddy covariance system over 2 months in a suburban area to complement the experimental results. Multifractal detrended fluctuation analysis and empirical mode decomposition are concertedly adopted to contrast multifractal properties of all sizes. The results reveal consistent multifractal behavior in both streamwise and vertical velocity fluctuations across laboratory and field datasets that consolidate a cascade mechanism regardless of physical dimensions. Aerodynamic resistance plays a critical role, enhancing multifractality due to intensified turbulent mixing and complex energy cascade. Multiscale analysis results demonstrate that the multifractal index exhibits a specific growth pattern: it initially increases, reaches a peak, then stabilizes thereafter with increasing scale. Both laboratory and field results indicate that ASL turbulence exhibits the most notable multifractal behavior at intermediate scales. Asymmetry analysis reveals a consistent transition from positive to negative across a range of surface roughness, indicating growing uniformity in smaller-scale processes. These results clarify how ground configuration influences turbulence intermittency and energy transfer in the urban atmospheric boundary layer, thereby improving the understanding of turbulent transport and multiscale airflow dynamics.
Wang et al. (Mon,) studied this question.