A IMPROVED PARAMETERIZATION SCHEME OF VERTICAL TURBULENT DIFFUSION

The parameterization problem of vertical turbulent diffusion in a Numerical Weather Prediction (NWP) model was addressed in this paper. Based on the turbulent scheme of Bougeault and Lacarrere (1989, referred as BL-89 scheme hereafter),the method for dealing with Turbulent Mixing Length (TML) was modified so that the dynamic TML and thermodynamic TML depend respectively upon the atmospheric static stability and wind shear. The basic idea of the new scheme is to combine the dynamic turbulent approach (wind shear) of Von Karman (1930) and the thermodynamic approach (static stability) of BL-89 scheme. It emphasis the comprehensive impacts of the atmospheric dynamic structure. thermodynamic structure and turbulent energy on the turbulent mixing. In comparison of the new scheme with the BL-89 scheme. it was concluded that under the conditions of stronger atmospheric static stability and wind shear. the new scheme has a better capability of representation of turbulent activities.