Numerical generation of inflow turbulence by cell perturbation technique in WRF simulation

This paper discusses the applicability of a cell perturbation technique to generation of micro-scale wind speed fluctuations in nested Weather Research and Forecasting (WRF) simulation. Multi-scale nesting simulations are conducted with different treatments for turbulence at different scale resolutions. Three outer and three inner nested domains adopt a Planetary Boundary Layer (PBL) scheme and Large Eddy Simulation (LES) model, respectively. Artificial cell perturbation of potential temperature is imposed at the innermost domain to accelerate turbulence development. In addition, five perturbation amplitudes and three perturbation cell sizes of potential temperature are examined at two wind speed levels to investigate the sensitivity of cell perturbation parameters in generating turbulence. The present study shows that the cell perturbation technique works to increase micro-scale wind speed fluctuation energy. Both perturbation amplitude and perturbation cell size play an important role in reproducing the power spectra at higher frequencies and turbulence intensities. It also shows that optimization of cell perturbation parameters is necessary to achieve specified turbulence statistics. The advantage of modeling various turbulence intensity profiles makes the cell perturbation technique adaptable to complex typhoon processes. •Artificial cell perturbation of potential temperature is imposed to accelerate turbulence development.•Micro-scale turbulence can be generated by cell perturbation with appropriate perturbation parameters.•Optimization of cell perturbation parameters is necessary in order to achieve specified turbulence statistics.