The suitability of Doppler lidar for characterizing the wind field above forest edges

Abstract

This study focuses on the usage of Doppler lidar to provide information about the turbulence structure above forest edges. Comparison with state-of-the-art laser Doppler anemometry measurements on a physical model in an atmospheric boundary layer wind tunnel shows that the lidar is able to resolve details of the wind field at a change of roughness in an appropriate order of magnitude. Measurements of real wind situations with moderate wind speed directed to and from the forest edge, as well as the investigation of a storm event with wind velocities of up to 45 m s-1, reflect well-known characteristics of the isolines of mean wind speed and its standard deviation and reproduce quantitative values of the wind field found in previous studies. The wide measuring zone of the lidar indicates an extent of the perturbation generated by the change of roughness at the forest edge of more than 30 tree heights in the horizontal and up to 6 tree heights in the vertical. A significant decrease in the integral length scale and an increase in the slope of the velocity spectra above the tree tops reflect the generation of smaller eddies in this region.