Turbulence closures in neutral boundary layers over complex terrain

In this work, three turbulence closure models, Mellor and Yamada level 2.5, E - l and E - ε implemented in a circulation model, are compared in neutral conditions over complex terrain. They are firstly applied to a one-dimensional case on flat terrain and then to a schematic two-dimensional valley. The simulation results, in terms of wind field and turbulent kinetic energy, are tested against measurements from a wind-tunnel experiment. The empirical constants defining the characteristic length scales of the closures are modified based on turbulence parameters estimated in the experiment. The formulation of the diffusion coefficients is analysed to explain the differences among the various closures in the simulation results. Regarding the mean flow, both on flat and complex terrain, all the closures yield satisfactory results. Concerning the turbulent kinetic energy, the best results are obtained by E - l and E - ε closures.