The impact of turbulence closure schemes on predictions of the mixed spectral finite-difference model for flow over topography

Impacts of different closure schemes in the Mixed Spectral Finite-Difference model (Beljaars et al., 1987) for neutrally stratified atmospheric surface-layer flow over complex terrain are studied. Six different closure schemes, Kappa (Z +z sub(0) ), Mixing Length, E- Kappa (Z +z sub(0) ), E- epsilon , E- epsilon - tau and q super(2) l are compared. Model results for flow over an infinite series of sinusoidal ridges are examined in the context of the inner and outer layers defined by Jackson and Hunt (1975). results are compared with rapid distortion estimates of the changes in normal stresses. The effects of streamline curvature are also examined in a qualitive sense.