The critical frequency of the large-scale vortices and the background turbulence in desert area

• This study investigated the critical frequency discriminating the large-scale vortices and the background turbulence.
• The critical frequency decreased with the reciprocal of the wall-normal distance.
• The critical frequency increased linearly with the inflow velocity.
• This study gave an empiricalformula of the critical frequency varying with wall-normal distance and inflow velocity.

Based on the analysis of the experimental data obtained in a desert area, this study investigated the variations of the critical frequency discriminating the large-scale vortices and the background turbulence with the distance above the ground surface and the inflow velocity. The results show that the critical frequency decreases with the reciprocal of the wall-normal distance and increases linearly with the inflow velocity. The effect of the surface properties were also considered in this study, and finally the fitting formula of the critical frequency with respect to the wall-normal distance and the inflow velocity was given.