Measurement of turbulence energy dissipation rate by a standalone high-resolution Doppler lidar

Abstract. A second-order structure function model for the lidar line of sight (LOS) velocities is proposed. This structure function model corrects for the turbulence filtering due to the probe volume averaging effect using a Gaussian weighting function. It takes advantage of the high range gate resolution of the BEAM 6x pulsed lidar used in this study, i.e., 3 m, to effectively resolve the inertial subrange. The structure function model is then used to obtain the turbulence energy dissipation rate (ε) by fitting the model over lidar measurements in the inertial subrange. Unlike previously presented structure function methods to evaluate ε in the literature, this method has a weaker dependence on the turbulence length scale. The estimated ε values obtained from the lidar are compared with the values obtained from ultrasonic anemometers at three heights: 103 m, 175 m, and 241 m. The comparison results show excellent correlation between the two sets, with a Pearson correlation coefficient (ρ) value of more than 0.9 at all three heights. The observed bias was also found to be very small, i.e., more than 50 % of all the lidar-measured ε values were found within ±20 % of the sonic-measured values. This method relies on the proper detection of the inertial subrange; hence, during very stable atmospheric conditions, the model fitting on the measurements produced relatively larger errors, due to the difficulty in detecting the inertial subrange. Applications of this method include, but are not limited to, quantifying turbulence in the wake of aircraft, understanding pollutant dispersion in urban environments, and wind resource and turbulence assessment in areas where erecting a meteorological mast is not possible.