Scanning coherent Doppler lidar is ideally suited for boundary layer measurements of the mean and turbulent velocity statistics. A 3D volume scan using a stack of PPI scans provides timely updates over a region of interest which is critical for producing the largest number of independent samples of the atmospheric processes which is difficult for other measurement systems such as towers and aircraft. However, to accurately estimate turbulent statistics, especially in regions of low turbulence, careful removal of the estimation error is critical [6]. There are critical lidar design issues since estimation error is smaller for a long lidar pulse but better spatial resolution is produced with a shorter pulse. For the CTI WindTracer system, the 66 m pulse width and 72 m range gate typically produces an estimation error σ_e ≈ 0.05 - 0.1 m/s which results in a correction to structure function estimates of 2σ_e~2 ≈ 0.005 - 0.02 which is feasible with current algorithms and 20 minutes of data [6] as indicated by the agreement to theoretical fits in Fig. 1. A shorter pulse system may require more accurate estimation error correction for these low turbulence conditions or a modification of the lidar operating parameters to reduce the estimation error with pulse accumulation [2].
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