A Motion-Correction Method for Turbulence Estimates from Floating Lidars

Abstract

Estimates of atmospheric turbulence performed by both fixed and floating vertically profiling, conically scanning wind lidars are affected by the measurement volume and turbulence structure, among others. We study this phenomenon by simulating the lidar measurements within synthetic fields of atmospheric turbulence. We use the simulations’ framework to assess the impact of buoy motions on turbulence estimation. Simulation results show that the buoy’s translational motions impact turbulence estimates the most. We also apply the simulation framework to analyze measurements from a floating lidar measuring nearby an offshore meteorological mast for a period of six months. The analysis of measurements is presented both without and with motion compensation. In general, we find from both simulations and measurements that the buoy motions do not impact the mean horizontal wind speed significantly, in agreement with previous studies. However, both simulations and measurements show that the standard deviation of the horizontal velocity is overestimated by the floating lidar. When we correct the measurements based on compensation factors derived from the simulations, the mean bias of the horizontal wind speed standard deviation changes from 18–19% to 5–21%, with large reductions at the first four heights closest to the surface and a slight increase at the highest vertical level.

Keywords

• atmospheric flow
• floating lidar
• motion correction
• turbulence
• velocity spectra
• velocity variances