Impacts of forest inhomogeneities in edge flow: a momentum and turbulent kinetic energy budget analysis

Forest landscapes are often characterized by multiple forest edges modifying the airflow exchanges with the atmosphere. Most of our knowledge on edge flow comes from numerical and wind tunnel experiments from which the canopy was approximated horizontally homogeneous. To investigate the impacts of tree-scale inhomogeneities on the wind dynamics along a forest edge, large-eddy simulations have been perfomed over inhomogeneous canopies. The three-dimensional forest structure is prescribed in the model from high resolution helicopter-based LiDAR scans of the Falster island forest in Denmark. Several simulations were performed to study the effect of different spatial configurations of the canopy structure on the flow. The simulations show that inhomogeneities induce significant dispersive fluxes at the forest leading-edge. These fluxes result from the spatial-variability of the flow as it penetrates through the sparsest regions of the edge. We show how the inhomogeneities change the momentum and energy transfers along the edge by performing a detailed momentum and turbulent kinetic energy budget analysis. The magnitude of the dispersive fluxes is then compared following the degree of inhomogeneities of the canopy.