COHERENT DOPPLER LIDAR SIGNAL COVARIANCE INCLUDING WIND SHEAR AND WIND TURBULENCE

The performance of a coherent Doppler lidar is determined by the stati stics of the coherent Doppler signal. The derivation and calculation o f the covariance of the Doppler lidar signal for random atmospheric wi nd fields and wind shear are presented. The signal parameters are defi ned for a general coherent Doppler lidar system in terms of the atmosp heric parameters. There are two distinct physical regimes: one in whic h the transmitted pulse determines the signal statistics and the other in which the wind field and the atmospheric parameters dominate the s ignal statistics. When the wind fields dominate the signal statistics, Doppler lidar data are nonstationary and the signal correlation time is proportional to the operating wavelength of the lidar. The signal c ovariance is derived for signal-shot and multiple-shot conditions. For a single shot, the parameters of the signal covariance depend on the random, instantaneous atmospheric parameters. For multiple shots, vari ous levels of ensemble averaging over the temporal scales of the atmos pheric processes are required. The wind turbulence is described by a K olmogorov spectrum with an outer scale of turbulence. The effects of t he wind turbulence are demonstrated with calculations for a horizontal propagation path in the atmospheric surface layer.