Investigating links between turbulence anisotropy and TKE budget by means of Large Eddy Simulations.

Monin-Obukhov Similarity Theory (MOST) is the workhorse for parametrizing first and second-order statistics in the atmospheric surface layer (ASL). First developed for homogeneous, stationary flows without subsidence. Later, it has been used for a wider range of flow conditions. However, it has been shown to break down in flows over complex topography and dense canopies. Recent developments have shown that turbulence anisotropy can be used to generalize MOST formulations for flows over all types of complex surface conditions. Additionally, MOST has been shown to work well in instances where a balance exists between turbulence production and dissipation. Thus, this work investigates the relation between production-dissipation imbalance and turbulence anisotropy in the ASL. For this, we use a suite of Large Eddy Simulations over different terrain configurations. Initial results indicate a relation between the anisotropy invariant y_B and the imbalance in the TKE budget. A threshold value of y_B ≈ 0.37 seems to separate between those instances in which the TKE imbalance is significant and positive from those in which it is close to zero. A considerable negative correlation is found between the decreasing percentage in the TKE residual and increasing anisotropy invariant y_B. Finally, we investigate the meaning of the y_B threshold value in relation to the return to isotropy and its meaning as a global scaling variable for first and second-order statistics of different turbulent flows.