EFFECTS OF WIND TURBULENCE ON COHERENT DOPPLER LIDAR PERFORMANCE

The effects of wind turbulence on pulsed coherent Doppler lidar perfor mance are investigated theoretically and with computer simulations. Th e performance of velocity estimators is determined for the case of a s ingle realization of a wind field described by a Kolmogorov spatial sp ectrum and for an ensemble average over many realizations. The results are compared with previously published data. The important normalized physical parameters are identified to reduce the parameter space. For a given realization of a random wind field, the mean Doppler lidar ve locity (an ensemble average over the random aerosol particles) is a fu nction of the lidar parameters and the instantaneous radial velocity o ver the sensing volume of the lidar pulse. Various approximations for the mean Doppler lidar velocity are compared using computer simulation s. The best approximation for the mean Doppler lidar velocity is used to calculate the effects of the spatial averaging of the radial veloci ty by the lidar pulse on Doppler lidar estimates of the spatial struct ure function of the velocity and the variance of the velocity. Doppler lidar estimates of point statistics of the wind field (velocity varia nce, spatial velocity structure function, energy dissipation rate) are possible for certain conditions. Using numerical simulations, the sta tistical description of common velocity estimators is determined by pe rforming the ensemble average over many realizations of a stationary w ind field, Velocity estimator error extracted from 2-mu m coherent Dop pler lidar data in the surface layer are shown to be within 5% of simu lation results that include the effects of wind turbulence. For typica l surface-layer measurements, a linear array of in situ wind sensors a long the lidar propagation direction would be required to produce reli able comparison of in situ measurement with coherent Doppler lidar win d measurements. The effects of wind turbulence on the performance of 2 - and 10-mu m coherent Doppler lidars for space-based operation are al so presented.