Turbulence closures in neutral boundary layer over complex terrain

In this work, three turbulence closure models, Mellor and Yamada level 2.5, E - l and E - epsilon implemented in a circulation model, are compared in neutral condition over complex terrain. They are firstly applied to a one-d imensional case on flat terrain and then to a schematic two-dimensional val ley. The simulation results, in terms of wind field and turbulent kinetic e nergy, are tested against measurements from a wind-tunnel experiment. The e mpirical constants defining the characteristic length scales of the closure s are modified based on turbulence parameters estimated in the experiment. The formulation of the diffusion coefficients is analysed to explain the di fferences among the various closures in the simulation results. Regarding t he mean flow, both on flat and complex terrain, all the closures yield sati sfactory results. Concerning the turbulent kinetic energy, the best results are obtained by E - l and E - epsilon closures.