A review of turbulence measurements using ground-based wind lidars

Abstract

Abstract.A review of turbulence measurements using ground-based wind lidars is carried out. Works performed in the last 30 yr, i.e., from 1972-2012 are analyzed. More than 80 % of the work has been carried out in the last 15 yr, i.e., from 1997-2012. New algorithms to process the raw lidar data were pioneered in the first 15 yr, i.e., from 1972-1997, when standard techniques could not be used to measure turbulence. Obtaining unfiltered turbulence statistics from the large probe volume of the lidars has been and still remains the most challenging aspect. Until now, most of the processing algorithms that have been developed have shown that by combining an isotropic turbulence model with raw lidar measurements, we can obtain unfiltered statistics. We believe that an anisotropic turbulence model will provide a more realistic measure of turbulence statistics. Future development in algorithms will depend on whether the unfiltered statistics can be obtained without the aid of any turbulence model. With the tremendous growth of the wind energy sector, we expect that lidars will be used for turbulence measurements much more than ever before.

Errors in radial velocity variance from Doppler wind lidar

“…Accordingly, uncertainties in lidar-derived mean wind velocity estimates have been well characterized Lindelöw-Marsden, 2009) and methods and procedures have been developed for error reduction and uncertainty control (Clifton et al, 2013;Gottschall et al, 2012). However, use of lidar for turbulence measurements, while possible (Newman et al, 2016;Branlard et al, 2013;Mann et al, 2010), is less established (Sathe et al, 2015;Sathe and Mann, 2013). Two methods are commonly used to derive the second-order moments (i.e., velocity variances and momentum fluxes) of turbulent flow from lidar data (Sathe and Mann, 2013).…”

“…The first method can suffer from cross-contamination errors (biases) due to the correlation between the radial velocities used for wind velocity estimates (Sathe et al, 2011). Therefore, the second method is considered to be more suitable for lidar turbulence measurements (Newman et al, 2016;Sathe et al, 2015;Sathe and Mann, 2013;Mann et al, 2010) Using the second method mentioned above, errors in the estimated variances and momentum fluxes are accumulations of the following three types of errors in the estimated radial velocity variance:…”

“…-attenuation errors due to the volumetric averaging effect of lidar measurement (Sathe and Mann, 2013;Mann4124 H. Wang et al: Errors in radial velocity variance from Doppler wind lidar -sampling errors as a result of estimating the ensemble mean by the time average (Mann et al, 2010;Lenschow et al, 1994).…”

“…However, use of lidar for turbulence measurements, while possible (Newman et al, 2016;Branlard et al, 2013;Mann et al, 2010), is less established (Sathe et al, 2015;Sathe and Mann, 2013). Two methods are commonly used to derive the second-order moments (i.e., velocity variances and momentum fluxes) of turbulent flow from lidar data (Sathe and Mann, 2013). The first method initially estimates the three orthogonal wind components from radial velocities acquired through a scan geometry (e.g., the conical scan) and then uses the eddy covariance method to derive the turbulence statistics.…”

Untitled

“…Turbulence estimation from lidar measurements has received a lot of attention in the literature and a summary is provided by Sathe and Mann (2013). Here, we require a pragmatic and robust method for scaling the Doppler lidar wind gusts independent of meteorological mast measurements.…”