Radar Wind Profiler Radial Velocity: A Comparison with Doppler Lidar

Abstract

The accuracy of the radial wind velocity measured with a radar wind profiler will depend on turbulent variability and instrumental noise. Radial velocity estimates of a boundary layer wind profiler are compared with those estimated by a Doppler lidar over 2.3 h. The lidar resolution volume was much narrower than the profiler volume, but the samples were well matched in range and time. The wind profiler radial velocity was computed using two common algorithms [profiler online program (POP) and National Center for Atmospheric Research improved moments algorithm (NIMA)]. The squared correlation between radial velocities measured with the two instruments was R2 = 0.99, and the standard deviation of the difference was about σr = 0.20?0.23 m s?1 for radial velocities of greater than 1 m s?1 and σr = 0.16?0.35 m s?1 for radial velocities of less than 1 m s?1. Small radial velocities may be treated differently in radar wind profiler processing because of ground-clutter mitigation strategies. A standard deviation of σr = 0.23 m s?1 implies an error in horizontal winds from turbulence and noise of less than 1 m s?1 for a single cycle through the profiler beam directions and of less than 0.11?0.27 m s?1 for a 30-min average measurement, depending on the beam pointing sequence. The accuracy of a wind profiler horizontal wind measurement will also depend on assumptions of spatial and temporal inhomogeneity of the atmosphere, which are not considered in this comparison. The wind profiler radial velocities from the POP and NIMA are in good agreement. However, the analysis does show the need for improvements in wind profiler processing when radial velocity is close to zero.