Effects of refractive turbulence on ground-based verification of coherent Doppler lidar performance

Retrieval of Microscale Wind and Temperature Fields from Single- and Dual-Doppler Lidar Data

Dual-Doppler lidar observations are used to assess the accuracy of single-Doppler retrievals of microscale wind and temperature fields in a shear-driven convective boundary layer. The retrieval algorithm, which is based on four-dimensional variational data assimilation, is applied by using dual- and single-Doppler lidar data that are acquired during the Joint Urban 2003 field experiment. The velocity field that was retrieved using single-Doppler data is compared directly with radial velocities that were measured by a second noncollocated lidar. Dual-Doppler retrievals are also performed and then compared with the single-Doppler retrieval. The linear correlation coefficient and rms deviation between the single-Doppler retrieval and the observations from the second lidar are found to be 0.94 and 1.2 m s−1, respectively. The high correlation is mainly the result of good agreement in the mean vertical structure as observed by the two lidars. Comparisons between the single- and dual-Doppler retrieval indicate that the single-Doppler retrieval underestimates the magnitude of fluctuations in the crossbeam direction. Vertical profiles of horizontally averaged correlations between the single- and dual-Doppler retrievals also show a marginal correlation (0.4–0.8) between one of the horizontal velocity components. Again, this suggests that the retrieval algorithm has difficulty estimating the crossbeam component from single-Doppler data.

Comment on "Heterodyne lidar returns in the turbulent atmosphere: performance evaluation of simulated systems"

The explanation proposed by Belmonte and Rye [Appl. Opt. 39, 2401 (2000)] for the difference between simulation and the zero-order theory for heterodyne lidar returns in a turbulent atmosphere is incorrect. The theoretical expansion the authors considered is not developed under a square-law structure-function approximation (random-wedge atmosphere). Agreement between the simulations and the zero-order term of the theoretical expansion is produced for the limit of statistically independent paths (bistatic operation with large transmitter-receiver separation) when the simulations correctly include the large-scale gradients of the turbulent atmosphere.