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.

A Machine Learning Approach to Correct Turbulence Intensity measured by Floating Lidars

“…The NOAH site is located at approximately 5.42 km far from the Port of Blyth, England, UK. It hosts a metmast equipped with cup anemometers at 35, 52, 69, 86, and 103 m AMSL [14]. A total of 20 validation campaigns were performed in NOAH from 2017 to 2023.…”

“…In contrast, [11,12,13], have tackled the issue at higher frequency rates, 50Hz. Recently, Peña et al [14] proposed a more comprehensive approach that relies on extensive physical simulations to model the behavior of FLS-measured TI.…”

Experimental Evaluation of the Motion-Induced Effects for Turbulent Fluctuations Measurement on Floating Lidar Systems

“…Ref. [10] utilized simulated lidar profiler measurements within synthetic atmospheric turbulence fields to evaluate how buoy motions affect turbulence estimation. Their simulations revealed that translational motions of the buoy notably influenced the accuracy of turbulence estimates.…”

On the Retrieval of Surface-Layer Parameters from Lidar Wind-Profile Measurements

“…However, despite the abundant wind resource that can be found over the seas, offshore wind farm harvesting remains more expensive than its onshore counterpart. Additionally, the site's feasibility still relies on offshore meteorological masts (metmasts), which are very expensive to install and maintain [4].…”

“…During the last decade, floating Doppler wind lidars (FDWLs) have emerged as the wind-energy-industry preferred solution to replace the metmast because of their accuracy and attractive cost-benefit of installation and maintenance. Many studies have shown that 10 min averaged wind-speed measurements from FDWLs are numerically equivalent to reference observations from anemometers or fixed Doppler wind lidar (DWL) [4][5][6]. However, FDWLs cannot measure a number of the atmospheric parameters that instruments mounted on meteorological masts can, which restrains commercial acceptance of FDWLs as stand-alone sensing instrument.…”