Evaluating the Modulating Effect of Atmospheric Turbulence Anisotropy on Monin-Obukhov Similarity Theory on the Basis of Flux-Variance Scaling Relationships

Monin‒Obukhov similarity theory (MOST) serves as a cornerstone for turbulent parameterization in the atmospheric surface layer. However, its applicability over complex terrain is often limited. On the basis of observational data from an eddy covariance (EC) tower at the Atmospheric Boundary Layer Eco-Environment Shanghuang Observatory (ABLES), the influences of the Reynolds stress tensor properties (yB: the degree of turbulent anisotropy; β: the geometric inclination angle of the Reynolds stress tensor) on the flux‒variance relationships for the wind velocity component temperature, water vapor and carbon dioxide are systematically investigated. The results show that the turbulence anisotropy states in the study area exhibits a largely mixed state but is modulated by the wind direction. Both yB and β exhibit diurnal patterns governed by atmospheric stability. Furthermore, the influence of atmospheric stability on yB and β differs between stable and unstable stratification. With respect to the flux–variance relationships, the scaling relationships for the wind velocity components clearly depend on yB and β. The data corresponding to near-isotropic turbulence align more closely with the traditional MOST relations, whereas strongly anisotropic data exhibit significant deviations. Within the same yB group, the functional curve describing the flux‒variance relationship is observed to exhibit a monotonic upward shift as β. This demonstrates that a generalized scaling framework incorporating the Reynolds stress tensor properties can effectively enhance the applicability of the MOST for wind velocity. However, Due to the complexity of scalar turbulence, the flux‒variance relationships for scalars do not exhibit dependencies on yB and β.