Coherent Wind Lidar Research Articles

Numerical optimization of auxiliary biaxial receiver to detect blind zone of pulsed coherent wind lidar.

The conventional pulsed monostatic coaxial coherent Doppler wind lidar (CDWL) has a blind detection zone of tens of meters, causing the loss of near-field wind field data. While maintaining the long-range detection capabilities of pulsed lidar, we introduce a novel auxiliary biaxial receiver (ABR) aimed at acquiring dependable coherent signals within blind zones. This is achieved by incorporating a receiver in close proximity to the monostatic coaxial transceiver (MCT), thereby mitigating end-face reflections and laser pulse tailing effects. A specific model of multiple aperture coherent wind detection is established for the ABR system without blind zone problem (BZP). The numerical simulations demonstrate that the biaxial receiver with reasonable design can meet the detection needs of the entire range of the blind zone. By using an ABR with a smaller focal length under appropriate transceiver pointing and general pointing accuracy, the BZP can be solved. The study also exhaustively obtained all parameter combinations that can solve the near-field BZP for a specific system. The results provide a new idea and engineering design guidance for the optical system design of pulsed CDWL without BZP.

Real-Time Synchronous Acquisition and Processing of Signal in Coherent Doppler Wind Lidar Using FPGA

Coherent Doppler wind lidar has become a primary remote sensing technique for measuring atmospheric wind fields in recent years. However, the high bandwidth of the time domain echo signal has limited real-time data acquisition and processing. In this work, we propose a real-time data acquisition and preprocessing integrated solution. This approach is implemented using on-chip system field programmable gate array (FPGA) hardware while utilizing a 7-channel base-4 polyphase fast Fourier transform calculation module and a pipelined structure operation. Within a 1 s data collection time, the real-time rapid acquisition and spectral preprocessing of lidar echo signals at a range of 9.9 km can be achieved. We compare the observation data with the measurement data from Windcube100s and radiosondes, and the results indicate that the coherent wind lidar developed in this paper can detect heights above 4.0 km, with effective data acquisition rates of 82% and 61% in the height ranges of 1500–2000 m and 2000–2500 m, respectively. At the height range of 3.5 km, the correlations for horizontal wind speed and direction measured by the lidar were all above 0.99, with the wind speed and direction measurement deviations being better than 0.56 m/s and 8.40∘, respectively.

4.08 mJ, 0.976 μs Er: YAG ring laser oscillator

Er:YAG ring laser with high-energy and wide pulse duration, which is resonantly pumped by a fiber laser at 1532 nm, is reported in this paper. Maximum power 2.62 W was implemented from ring resonator at 1645 nm. By transforming pulse repetition frequency (PRF), pulsed output energy was 4.08 mJ under 100 Hz PRF with a pulse width of 0.976 μs under the Q-switching regime. Since the wind measurement accuracy of coherent wind lidar is determined by the pulse width of the emission laser, this 1.6 µm single-frequency laser with high energy and wide pulse width is an ideal laser source for coherent wind lidar.

Performance simulation of space-based coherent wind LIDAR system under various meteorological conditions

Performance simulation of space-based coherent wind LIDAR system under various meteorological conditions

Research on high resolution range-gate adaptive technology of coherent wind lidar

Research on high resolution range-gate adaptive technology of coherent wind lidar

相干测风激光雷达的数值建模和仿真分析

相干测风激光雷达的数值建模和仿真分析

Performance Optimization and Experimental Research of Continuous Wave Coherent Wind Lidar

Performance Optimization and Experimental Research of Continuous Wave Coherent Wind Lidar

A high signal-to-noise ratio balanced detector system for 2 μm coherent wind lidar

A balanced detector system with a high signal-to-noise ratio (SNR) is the key technology for 2 μm coherent wind lidar, which can enhance the ability for the digital receiver to detect extremely weak signals. The photodiode is the main detection component of a balanced detector system. The variance of junction capacitance of different photodiodes will cause the degradation of SNR. Based on the linear relationship between the junction capacitance of a photodiode and the reverse voltage in the double logarithmic coordinates, a balanced detector system is designed to have the ability to adjust the reverse voltage by using the external digital-to-analog converter. An optimization of the circuit performance can be achieved by adjusting the junction capacitance, which significantly affects the circuit noise and signal bandwidth in the design of the high bandwidth transimpedance amplifier, which is sensitive to parasitic capacitance and component error. A simplified optical system is built to test the performance of the designed balanced detector system. The results show that the SNR of the detector system is ∼10% higher than that of the commercial product, which can further increase the detection distance of the wind lidar by ∼1.5 km for the detection limit of 10 km.

Intercomparison of wind observations from the European Space Agency's Aeolus satellite mission and the ALADIN Airborne Demonstrator

Abstract. Shortly after the successful launch of the European Space Agency's wind mission Aeolus, co-located airborne wind lidar observations were performed in central Europe; these observations employed a prototype of the satellite instrument – the ALADIN (Atmospheric LAser Doppler INstrument) Airborne Demonstrator (A2D). Like the direct-detection Doppler wind lidar on-board Aeolus, the A2D is composed of a frequency-stabilized ultra-violet (UV) laser, a Cassegrain telescope and a dual-channel receiver to measure line-of-sight (LOS) wind speeds by analysing both Mie and Rayleigh backscatter signals. In the framework of the first airborne validation campaign after the launch and still during the commissioning phase of the mission, four coordinated flights along the satellite swath were conducted in late autumn of 2018, yielding wind data in the troposphere with high coverage of the Rayleigh channel. Owing to the different measurement grids and LOS viewing directions of the satellite and the airborne instrument, intercomparison with the Aeolus wind product requires adequate averaging as well as conversion of the measured A2D LOS wind speeds to the satellite LOS (LOS*). The statistical comparison of the two instruments shows a positive bias (of 2.6 m s−1) of the Aeolus Rayleigh winds (measured along its LOS*) with respect to the A2D Rayleigh winds as well as a standard deviation of 3.6 m s−1. Considering the accuracy and precision of the A2D wind data, which were determined from comparison with a highly accurate coherent wind lidar as well as with the European Centre for Medium-Range Weather Forecasts (ECMWF) model winds, the systematic and random errors of the Aeolus LOS* Rayleigh winds are 1.7 and 2.5 m s−1 respectively. The paper also discusses the influence of different threshold parameters implemented in the comparison algorithm as well as an optimization of the A2D vertical sampling to be used in forthcoming validation campaigns.

Performance of Continuous-wave Coherent Doppler Lidar for WindMeasurement

A system for continuous-wave coherent Doppler lidar (CW lidar), made up of all-fiber structures and a coaxial transmission telescope, was set up for wind measurement in Hefei (31.84 N, 117.27 E), Anhui province of China. The lidar uses a fiber laser as a light source at a wavelength of 1.55 μm, and focuses the laser beam on a location 80 m away from the telescope. Using the CW lidar, radial wind measurement was carried out. Subsequently, the spectra of the atmospheric backscattered signal were analyzed. We tested the noise and obtained the lower limit of wind velocity as 0.721 m/s, through the Rayleigh criterion. According to the number of Doppler peaks in the radial wind spectrum, a classification retrieval algorithm (CRA) combining a Gaussian fitting algorithm and a spectral centroid algorithm is designed to estimate wind velocity. Compared to calibrated pulsed coherent wind lidar, the correlation coefficient for the wind velocity is 0.979, with a standard deviation of 0.103 m/s. The results show that CW lidar offers satisfactory performance and the potential for application in wind measurement.

相干测风激光雷达研究进展和应用

相干测风激光雷达研究进展和应用

连续相干探测激光风速仪设计与测试

In order to implement measurement of the close wind field accurate and real-time, a laser anemometer based on CW coherence detection was designed with eye-safe band 1.55 m. The system optical path employed the all-fiber structure to enhance the operational stability. The telescope adopted a coaxial transmission structure with effective aperture of 70 mm and focusing distance of 80 m. The backscattered signals were processed by using the on-board programmable gate array chip on the A/D capture card and spectral centroid algorithm was also designed for wind velocity estimation. The anemometer realized high real-time and reliability. The long-term radial wind speed measurement results proved that the laser anemometer output signal was stable with a time resolution of 1 s and the lower limit of the wind measurement range was about 0.915 m/s. Compared with a calibrated pulsed coherent wind lidar, the correlation coefficient of wind speed data measured by the two devices was 0.997, the standard deviation was 0.090 m/s, and the maximum difference was 0.480 m/s.

光源线宽对相干激光测风雷达探测性能的影响分析

光源线宽对相干激光测风雷达探测性能的影响分析

Airborne wind lidar observations over the North Atlantic in 2016 for the pre-launch validation of the satellite mission Aeolus

Abstract. In preparation of the satellite mission Aeolus carried out by the European Space Agency, airborne wind lidar observations have been performed in the frame of the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX), employing the prototype of the satellite instrument, the ALADIN Airborne Demonstrator (A2D). The direct-detection Doppler wind lidar system is composed of a frequency-stabilized Nd:YAG laser operating at 355 nm, a Cassegrain telescope and a dual-channel receiver. The latter incorporates a Fizeau interferometer and two sequential Fabry–Pérot interferometers to measure line-of-sight (LOS) wind speeds by analysing both Mie and Rayleigh backscatter signals. The benefit of the complementary design is demonstrated by airborne observations of strong wind shear related to the jet stream over the North Atlantic on 27 September and 4 October 2016, yielding high data coverage in diverse atmospheric conditions. The paper also highlights the relevance of accurate ground detection for the Rayleigh and Mie response calibration and wind retrieval. Using a detection scheme developed for the NAWDEX campaign, the obtained ground return signals are exploited for the correction of systematic wind errors. Validation of the instrument performance and retrieval algorithms was conducted by comparison with DLR's coherent wind lidar which was operated in parallel, showing a systematic error of the A2D LOS winds of less than 0.5 m s−1 and random errors from 1.5 (Mie) to 2.7 m s−1 (Rayleigh).

相干测风激光雷达VAD风场反演的数据质量控制方法

相干测风激光雷达VAD风场反演的数据质量控制方法

相干测风激光雷达微弱信号的频率估计

相干测风激光雷达微弱信号的频率估计

An Optimization Method of Local Oscillating Beam Power for Coherent Wind Lidar

The working principle and the influence factors of carrier-to-noise ratio of heterodyne detection are analyzed in this paper. The local oscillating beam power optimization method is proposed based on the saturation effect of photoelectric detector. Increasing the local oscillating beam power, the transpose gain can be increased, and then the detection limit of carrier-to-noise ratio can be reached. Too high local oscillating beam power will affect the precision of the photoelectric detector, then the photoelectric detector works in the nonlinear region, therefor the carrier-to-noise ratio is reduced. In this paper, the optimization strategy of carrier-to-noise ratio is proposed via analyzing the relationships between the heterodyne signal and the local oscillating beam power, the noise and the local oscillating beam power. The experimental results show that the optimal power of the local oscillating beam can be obtained for different working wavelengths of local oscillating beam by the optimization method proposed.

Observations of water vapor mixing ratio profile and flux in the Tibetan Plateau based on the lidar technique

Abstract. As a part of the third Tibetan Plateau Experiment of Atmospheric Sciences (TIPEX III) in China, a Raman water vapor, cloud and aerosol lidar and a coherent wind lidar were operated in Naqu (31.48° N, 92.06° E) with a mean elevation of more than 4500 m a.m.s.l. in summer of 2014. During the field campaign, the water vapor mixing ratio profiles were obtained and validated by radiosonde observations. The mean water vapor mixing ratio in Naqu in July and August was about 9.4 g kg−1 and the values vary from 6.0 to 11.7 g kg−1 near the ground according to the lidar measurements, from which a diurnal variation of water vapor mixing ratio in the planetary boundary layer was also illustrated in this high-elevation area. Furthermore, using concurrent measurements of vertical wind speed profiles from the coherent wind lidar, we calculated the vertical flux of water vapor that indicates the water vapor transport through updraft and downdraft. The fluxes were for a case at night with large-scale non-turbulent upward transport of moisture. It is the first application, to our knowledge, to operate continuously atmospheric observations by utilizing multi-disciplinary lidars at the altitude higher than 4000 m, which is significant for research on the hydrologic cycle in the atmospheric boundary layer and lower troposphere in the Tibetan Plateau.

相干测风激光雷达中多核DSP并行风速反演算法的实现

相干测风激光雷达中多核DSP并行风速反演算法的实现

相干测风激光雷达中多核DSP并行风速反演算法的实现

相干测风激光雷达中多核DSP并行风速反演算法的实现