Subgrid scale modelling of the flux of the motion quantity and heat in isotropic three-dimensional turbulence

Techniques for modelling small-scale motion and heat flux parameters for inclusion in meteorological models for weather forecasting are described. The small-scale processes are assumed isotropic and finite difference equations are used for the calculations, which cover values in Fourier space in order to account for interactions between the small and the large scale processes of the atmosphere. The subgrid transfers of the motion quantity and heat are aided by quantification of the viscosity and turbulent diffusivity in spectral space in terms of the evolution of energy and temperature. Sample simulations reveal that the calculation of the viscosity and turbulent diffusivity yields results similar to those obtained with a -5/3 power law wavenumber cutoff formulation.