A study on new turbulence parameterization with utilization of numerical and wind-tunnel experiments

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An appropriate formulation of parameterized turbulent motions is absolutely essential for reproducing turbulent transfer in the atmospheric boundary layer with a numerical model. The following studies are conducted in order to improve turbulence parameterization schemes used in the Large-Eddy Simulation (LES) and the Reynolds Averaged Numerical Simulation (RANS). First, we perform a set of numerical simulations based on the LES in a moderately stable boundary layer and attempt to evaluate the error of the vertical flux in terms of self-consistency, based on the Germano identity. Second, to solve problems with the Mellor-Yamada-Nakanishi-Niino (MYNN) model, we attempted to modify a relaxation time scale of temperature-pressure correlation for the stable stratification case. In contrast to the original MYNN model, the modified model has no critical Richardson number, and the effect of turbulent motions remains for all Richardson number values in the level 2 model. Lastly, we perform numerical and wind-tunnel experiments to identify dependence of flux Richardson number on atmospheric static stability. These results indicate that flux Richardson number can be over unity.