Measurements of turbulent energy dissipation rate with a CW Doppler lidar in the atmospheric boundary layer

The results of a theoretical and experimental study of the feasibility of t he turbulent energy dissipation rate epsilon(T) measurements with a continu ous wave (CW) CO, Doppler lidar in the atmospheric boundary layer are prese nted. Three methods of probing epsilon(T) are considered: 1) Doppler spectr um width. 2) the temporal spectrum (temporal structure function) of wind ve locity measured by the Doppler lidar, and 3) spatial structure function. In these methods, information on the dissipation rate is extracted by means o f analysis of thr corresponding statistical characteristics of wind velocit y in the inertial subrange of the turbulence, laking into account the spati al averaging of the measured wind velocity fluctuations over sounded volume . In the first and third methods, the spatial structure of the turbulence is analyzed directly. In the second method, to determine epsilon(T) from the m easured temporal characteristics, it is necessary to use a model for the sp atiotemporal correlation function of wind velocity. As a result of the stud y, it has been shown that in the case of large longitudinal size of sounded volume and weak side wind, Taylor's hypothesis of "frozen" turbulence cann ot he accepted for the correlation function. The strict limitation on the l ongitudinal size of the sounded volume and therefore sounding height is the main restriction of the first method. The third method is free of such lim itations. It allows one to obtain the information on the dissipation rate p rofile throughout the entire boundary layer. Comparison of the developed th eory for statistical characteristics of wind velocity measured by the Doppl er lidar with the obtained experimental data has demonstrated their good ag reement. The vertical profiles of the turbulent energy dissipation rate retrieved fr om Doppler lidar data with the use of the methods described above do not co ntradict the known experimental results. This fact confirms the feasibility of application of lidar remote sensing methods to the study of the small-s cale turbulence in the atmospheric boundary layer.