WindScanner measurements of turbulence

In this report we present how to estimate turbulence measures and unfiltered radial velocity variances from long-range WindScanners, which are pulsed scanning lidars. We also show how the radial velocity spectrum, and thus the radial velocity variance, are a function of the turbulence structure and the misalignment of the lidar beam with the mean wind.

Moreover, we show how to optimize scanning strategies for scanning lidars in order to measure turbulence assuming that we are able to estimate the unfiltered radial velocity variance; we illustrate a method to estimate the relative error in turbulence estimates for a given configuration. Further, we show how to estimate the velocity component variances, which are those needed for site assessment, by combining second-order statistics of the radial velocities of multiple scanning lidars.

Results of second-order statistics of radial velocities and velocity components performed at an experimental campaign carried out at the Høvsøre test station, where two WindScanners pointed close to a sonic anemometer during about one month, are illustrated and compared to theoretical computations.