Using a pulsed coherent Doppler lidar, the effect of an internal gravity wave (IGW) propagating in a thermally stable atmospheric boundary layer on the shape of the spectral density of the vertical component of the wind velocity vector is experimentally studied. It has been established that the presence of IGW causes a significant change in the shape of the velocity spectrum at frequencies below the frequencies of the turbulence inertial subrange. In this case, between the IGW frequency and the lower frequency boundary of the inertial subrange, the spectrum has a power-law dependence on frequency. By analyzing the data of 700 lidar estimates of the spectral density of the vertical wind speed, it was found that the exponent is on average -3.
The calculation time and the error of the estimates of the horizontal wind velocity from the data of the conical scan are compared. Various implementations of algorithms for direct and filtered sinusoidal wave fitting, and machine learning algorithms based on boosted decision trees (BDT), are being tested. The paper presents the advantages and disadvantages of these algorithms in numerical simulation and experimental data, obtained during measurements with pulse coherent Doppler lidar.
A pulsed coherent Doppler lidar (PCDL) developed at the Wave Propagation Laboratory of the Institute of Atmospheric Optics SB RAS (WPL lidar) was tested in two experiments conducted in 2021 at the Basic Experimental Observatory of the Institute of Atmospheric Optics SB RAS and on the coast of Lake Baikal. In these experiments, the Stream Line PCDL of serial production from HALO Photonics (Great Britain) was also involved. A comparative analysis of estimates of the average horizontal and vertical wind speeds from measurements by Stream Line and WPL lidars showed good agreement between the results (with a 30-minute averaging of the data, the correlation coefficient of the estimates is 0.98).
A comparison is made of the time variations in the height of the turbulent mixing layer, which is determined from the
altitude-time distributions of the dissipation rate of the kinetic energy of turbulence and from the distributions of the
Richardson number Ri . It is shown that qualitatively the time series of the height of the turbulent mixing layer,
calculated according to the threshold value of the dissipation rate Thrɛ= 10-4 м2/с3 and according to the criterion
Ri <0.5, agree with each other.
The paper presents a new approach to implement the method of accumulating real autocorrelation functions on FPGAs to estimate the wind velocity from the signal of a pulsed coherent Doppler wind lidar. The proposed method provides lower resource consumption compared to the implementation of the method accumulation of power spectra.
A method has been developed for estimating the turbulent energy dissipation rate and the variance of the radial velocity from the spectral density of the vertical wind velocity measured by a pulsed coherent Doppler lidar (PCDL). To obtain unbiased estimates of such wind turbulence parameters, the averaging of the radial velocity over the probed volume is taken into account. The method was tested in a numerical experiment, as well as in an experiment on the territory of the Basic Experimental Observatory of the IAO SB RAS using the Stream Line PCDL.
To determine the degree of anisotropy of wind turbulence from measurements by a Stream Line lidar during the experiment, we used a conical scanning by the probing beam, alternately setting the elevation angle of 35.3° and 60° after each scan. An experiment with such measurement geometry was carried out by us at the Basic Experimental Station of the IOA SB RAS in July 2018. Analysis of the measurement results at night in the presence of a low-level jet (LLJ) in the atmosphere showed that the variance (integral scale) of the horizontal component of the wind speed is 2.26 (3.4) times larger than the variance (integral scale) of the vertical component. In the central part of the LLJ, the integral scales of the horizontal and vertical components of wind speed are on average equal to 183 m and 54 m, respectively.
This paper describes a pulsed coherent Doppler lidar, recently created at the Wave Propagation Laboratory of the Institute of Atmospheric Optics SB RAS (WPL lidar). The WPL lidar was tested in atmospheric experiments. Comparison of the results of joint measurements of the radial velocity by the WPL lidar and Stream Line lidar showed their satisfactory agreement. From measurement of radial velocities by the WPL lidar at various azimuth angles (that is, with the use of the conical scanning), the height profiles of wind velocity and wind direction angle in the atmospheric boundary layer have been retrieved.
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