On the Velocity Gradient in Stably Stratified Sheared Flows. Part 2: Observations and Models

摘要

Observations of the dependence of the dimensionless wind speed gradient [graphic removed] as a function of the Monin-Obukhov stability parameter z/L o under strong stability diverge from results of large-eddy simulation (LES) modelling. A kinetic energy budget analysis indicates that it is likely caused by violations of the assumptions of stationarity and/or homogeneity of turbulence in the field experiments rather than in imperfections of the LES. This confirms the validity of the widely used linear approximation for [graphic removed] not only at weak to moderate stability, but also under strong stability. The new interpretation of the linear approximation of [graphic removed] is given in terms of turbulent scales, which gives hope for its applicability to the free atmosphere as well.