@book{e1db40c46063444a84bf70b7230d8526,

title = "Investigation of turbulence measurements with a continuous wave, conically scanning LiDAR",

abstract = "LIDAR systems are getting more and more accurate and reliable. It has been shown many times that the mean horizontal wind speed measured by a lidar over flat terrain compares very well with that measured by a cup anemometer. But can a lidar measure turbulence? Here we investigate the case of a continuous wave, conically scanning Zephir lidar. First, the wind speed standard deviation measured by such a lidar gives on average 80{\%} of the standard deviation measured by a cup anemometer. This difference is due to the spatial averaging inherently made by a cw conically scanning lidar. The spatial averaging is done in two steps: 1) the weighted averaging of the wind speed in the probe volume of the laser beam; 2) the averaging of the wind speeds occurring on the circular path described by the conically scanning lidar. Therefore the standard deviation measured by a lidar resolves only the turbulence structures larger than a length scale depending on the circle diameter and the mean wind speed (range of magnitude: 100m). However, the Zephir lidar gives another turbulence quantity, the so-called turbulence parameter, which can resolve turbulence structures with a smaller length scale. In this paper, we suggest a volumetric filtering of the turbulence to represent the effect of the spatial averaging operated by a lidar when measuring the wind speed. We then evaluate this model by comparing the theoretical results to experimental data obtained with several Zephir systems, for both turbulence quantities.",

keywords = "Wind energy, Test and measurements, Ris{\o}-R-1682, Ris{\o}-R-1682(EN), Test og m{\aa}linger, Vindenergi",

author = "Rozenn Wagner and Torben Mikkelsen and Michael Courtney",

year = "2009",

language = "English",

isbn = "978-87-550-3736-6",

series = "Denmark. Forskningscenter Risoe. Risoe-R",

number = "1682(EN)",

publisher = "Danmarks Tekniske Universitet, Ris{\o} Nationallaboratoriet for B{\ae}redygtig Energi",

}