, Volume 36, Issue 1-2, pp 53-70

A comparative assessment of mixing-length parameterizations in the stably stratified nocturnal boundary layer (NBL)

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Abstract

A one-dimensional model based on the equations of mean motion and turbulent kinetic energy (TKE) with a mixing-length closure scheme has been developed to simulate the turbulence structure of the evolving stably stratified nocturnal boundary layer (NBL). The model also includes a predictive equation for the surface temperature with parameterization of longwave radiational cooling.

Sensitivity tests, including a comparative study of the various mixing-length schemes found in the literature, have shown that variations in those formulations affect the turbulent flux profiles to a much larger extent than they affect the mean profiles. Heat and momentum fluxes when normalized by their surface values and represented as functions of z/h are not so sensitive to the mixing-length formulation; however, normalized TKE, eddy viscosity and energy dissipation strongly depend on the mixing-length formulation used.

Detailed comparisons between model predictions and a limited number of measurements taken on the Cabauw tower have shown that Delage's (1974) formulation performed better than the other schemes in describing vertical profiles and temporal behavior of the mean and turbulent variables. Since there are only very few experimental studies of the NBL, recommendations are made for a comprehensive field study of the same.