Intercomparisons of clear-air vertical air motion measurements from cloud radar, Doppler lidar, and wind profiler

Vertical air motion measurements in clear air (e.g., subcloud layer) are very important for the documentation of the turbulent structure of the convective boundary layer in cloud free and cloud-topped conditions. Active remote sensors such as Doppler cloud radars, Doppler lidars, and wind profilers offers three different scattering mechanisms for unique way of observing the vertical air motions in the lower troposphere. Cloud radars are sensitive to the tracers such as cloud droplets and insect echoes in the boundary layer, thereby mapping the vertical velocities with certain assumptions (e.g., tracers are passive or by correcting for their terminal velocities). The Doppler lidar operating at 1.5 ƒÝm is sensitive to aerosol particle motion, passive tracers of the air motion, thereby providing the accuracy vertical velocity measurements. Radar wind profiler operating at 915 MHz (ƒÜ=33 cm) on the other hand are sensitive to the inhomogeneity in the refractive index (Bragg Scattering), thereby vertical air motion can be retrieved by identifying the turbulent peak in the Doppler spectra. Collocated measurements from all these three platforms are now continuously available at the ARM SGP site and this provides the opportunity for intercomparison. The vertical velocity retrievals from the above three platforms are compared, and the vertical velocity statistics at different sampling volumes are discussed