The temperature of the middle atmosphere is of great significance in the coupled study of the upper and lower layers. A pure rotational Raman–Rayleigh scattering LiDAR system was developed for profiling the middle atmospheric temperature at daytime and nighttime continuously by employing an ultra-narrow band interferometer. The comparisons between LiDAR detections and radiosonde data show that the LiDAR system has temperature detection capabilities of 80 km and 60 km at night and during the day, respectively. The results demonstrate that our method can reliably detect the atmospheric temperature in the middle atmosphere. The significant non-uniformity in the horizontal distribution of temperature in the middle atmosphere and the vertical gradient of atmospheric temperature could be observed by using the developed LiDAR.

Single-mode, frequency-stabilized laser is a key component of a resonance fluorescence Doppler lidar, and the frequency of the laser emitting should be steadily locked on the resonance line of the metal atom. Here, a new Nd:YAG-based frequency-tripled source operating at 372 nm, which integrates an all-fiber-coupled seeder laser and an all-solid-state Nd:YAG laser, is developed for an iron resonance fluorescence Doppler lidar (Fe lidar). The saturation absorption spectrum of iodine near 558 nm is carried out for the first time, to our knowledge, to frequency stabilization, and the optical phase lock loop technique is used to realize the shift of seeder laser between three different frequencies. The seeder laser is injected into diode side-pumped Nd:YAG laser to generate a pulsed laser. An injection-seeded technique combined with an active cavity control technique (Ramp-fire) is applied to maintain resonance with the seeder laser and frequency stability of 864 kHz root mean square over 2 h is obtained. Laser power of about 1 W (∼16 mJ, 60 Hz) can be output after amplification and nonlinear frequency conversions. Lidar observation demonstrates that the developed source can be employed to profiling temperature and wind with high resolution and accuracy, and it can be a new choice for Fe lidar to observe atmospheric dynamics phenomena.

Integrated systems are facing complex and changing environments with the wide application of atmospheric LiDAR in civil, aerospace, and military fields. Traditional analysis methods employ optical software to evaluate the optical performance of integrated systems, and cannot comprehensively consider the influence of optical and mechanical coupling on the optical performance of the integrated system, resulting in the unsatisfactory accuracy of the analysis results. Optical–mechanical integration technology provides a promising solution to this problem. A small-field-of-view LiDAR system with high repetition frequency, low energy, and single-photon detection technology was taken as an example in this study, and the Zernike polynomial fitting algorithm was programmed to enable transmission between optical and mechanical data. Optical–mechanical integration technology was employed to obtain the optical parameters of the integrated system under a gravity load in the process of designing the optical–mechanical structure of the integrated system. The experimental validation results revealed that the optical–mechanical integration analysis of the divergence angle of the transmission unit resulted in an error of 2.586%. The focal length of the telescope increased by 89 μm, its field of view was 244 μrad, and the error of the detector target surface spot was 4.196%. The continuous day/night detection results showed that the system could accurately detect the temporal and spatial variations in clouds and aerosols. The inverted optical depths were experimentally compared with those obtained using a solar photometer. The average optical depth was 0.314, as detected using LiDAR, and 0.329, as detected by the sun photometer, with an average detection error of 4.559%. Therefore, optical–mechanical integration analysis can effectively improve the stability of the structure of highly integrated and complex optical systems.

Through theoretical calculations and field experiments, the setting of gate width in distance gating technology has been optimized in DIM LiDAR. The mathematical relationship between gate width and detection distance has been derived. The relationship curves between gate width and image signal-to-noise ratio(SNR), as well as gate width and atmospheric refractive index structure constant \(C_n^2\) were obtained. The results indicate that at a constant detection distance, there is a gradual increase in the SNR of the image with increasing gate width, followed by a saturation point. The higher the SNR, the closer the inverted $C_n^2$ is to the ultrasonic anemometer. Meanwhile, if the SNR is similar, the inverted $C_n^2$ is similar. Finally, the appropriate gate width for this system is given.

Atmospheric water vapor is a crucial factor in the Earth's water cycle. As an important greenhouse gas, changes in the spatio-temporal distribution of atmospheric water vapor can contribute to the occurrence of various extreme weather phenomena. Lidar, with its high spatial and temporal resolutions, has great potential for applications in water vapor profile detection. Raman lidar and differential absorption lidar (DIAL) have been successfully used to detect atmospheric water vapor. System calibration is crucial to ensure that the measured profile accurately represents the concentration profile of atmospheric water vapor. Choosing an effective system calibration method can ensure the accuracy of long-term lidar measurements. This paper reviews the latest progress and applications of atmospheric water vapor lidar calibration in recent years. The basic principles of Raman lidar and DIAL calibration are introduced. Various methods and benefits of system calibration are discussed. Raman lidar has three commonly used calibration methods: external calibration, internal calibration, and hybrid calibration methods. The most commonly used method is external calibration based on radiosondes. DIAL is usually implemented with an advantageous self-calibration method. Finally, potential development directions for atmospheric water vapor lidar and calibration technology are discussed.This article is categorized under: Science of Water > Methods Engineering Water > Methods Human Water > Value of Water

A denoising method applied to atmospheric coherent length lidar is proposed. Wavelet decomposition (WD) and the adaptive median filter (ADMF) are combined in this method. In this research, the effectiveness of the WD-ADMF has been verified through simulation and measurement. The results show that this filter algorithm, when applied to lidar data, improves the average peak signal-to-noise ratio (PSNR) and centroid error while maintaining data integrity such that the measurement of coherence length or the inference of C n 2 from coherence length more closely matches simulated truth and measured data.

In the study of atmospheric wind fields from the upper troposphere to the stratosphere (10 km to 50 km), direct detection wind LiDAR is considered a promising method that offers high-precision atmospheric wind field data. In 2020, Xie et al. of the Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, developed an innovative rotating Rayleigh Doppler wind LiDAR (RRDWL). The system aims to achieve single-LiDAR detection of atmospheric wind fields by rotating the entire device cabin. In 2022, the feasibility of the system was successfully validated in laboratory conditions, and field deployment was completed. Due to the structural differences between this system and traditional direct-detection wind LiDAR, performance tests were conducted to evaluate its continuous detection capability in outdoor environments. Subsequently, based on the test results and error analysis, further analysis was carried out to identify the main factors affecting the system’s detection performance. Finally, the error analysis and traceability of the detection results were conducted, and corresponding measures were discussed to provide a theoretical foundation for optimizing the performance of RRDWL.

An integrated LiDAR system has been reported, which can be used for simultaneous detection of atmospheric transmittance, turbulence, and wind along the same path. Through the integrated design of optics and mechanics, the size and weight of the system were effectively reduced. The comprehensive detection distance of atmospheric transmittance, atmospheric coherence length, and radial wind had also been achieved at least 4 kilometers. Comparative experiments have demonstrated that the detection results of the integrated LiDAR system and the near-surface meteorological observation system have standard deviations of less than 0.03 km-1 for extinction coefficient, 0.2 m/s for wind velocity, and 7.15 x 10-14 m-2/3 for C 2 n (atmospheric refractive index structure parameter), thus verifying the accuracy of the system detection. The reliability of the integrated LiDAR system was validated through six consecutive nights of continuous detection experiments, measuring three parameters simultaneously. Through analysis, the influence laws among atmospheric transmittance, coherence length, and wind were preliminarily explored. Significant variations in wind velocity can induce substantial fluctuations in atmospheric coherence length, and it is positively correlated with atmospheric transmittance. The integrated LiDAR system can provide a variety of reliable real-time detection data for further research on the laser transmission process in the atmosphere.

Through theoretical calculations and field experiments, the setting of gate width in distance gating technology has been optimized in DIM LiDAR. The mathematical relationship between gate width and detection distance has been derived. The relationship curves between gate width and image signal-to-noise ratio(SNR), as well as gate width and atmospheric refractive index structure constant C_n^2 were obtained. The results indicate that at a constant detection distance, there is a gradual increase in the SNR of the image with increasing gate width, followed by a saturation point. The higher the SNR, the closer the inverted C_n^2 is to the ultrasonic anemometer. Meanwhile, if the SNR is similar, the inverted C_n^2 is similar. Finally, the appropriate gate width for this system is given.

Due to weak echo signals that become progressively overwhelmed by noise, measurement accuracy and effective detection range of the Coherent Doppler wind LiDAR (CDL) are often compromised. While increasing the optical local-oscillator power (OLP) can amplify the echo signal, it is constrained by the nonlinear effects of the detector. This paper introduces a method for optimizing the OLP in CDL systems. Theoretical analysis has been proposed to explore the amplification effect of OLP on echo signals, and the nonlinear effects of detectors have been studied. Simulations are performed to explore the influence of varying OLP on the signal-to-noise ratio (SNR) across different detector alpha (quadratic nonlinear coefficient) values. The spectral analysis method is used to directly compute the SNR of actual atmospheric wind field signals under various OLP settings. Results demonstrate consistency between calculated and simulated values, enabling determination of optimal OLP and the detector alpha values from fitted curves. Comparative experiments confirm significant enhancement in effective detection range (> 1.5 km) with +/- 0 . 5 m/s accuracy. The innovation of this study lies in combining the OLP optimization method with real atmospheric wind field echo signal experiments. It addresses the challenges of directly measuring the nonlinear parameters of the detector and determining the optimal OLP. This study offers valuable theoretical and experimental insights for the wind measurement of CDL.

The detection principle of a multi-longitudinal-mode (MLM) Doppler lidar based on a quadri-channel Mach-Zehnder interferometer (QMZI) was analysed. The measurement error formulas for the radial wind speed and backscatter ratio of this type of Doppler lidar system were derived. The advantages of this detection technology were thoroughly analysed based on the principle. The optical path difference (OPD) 'l' between the two interference arms of the QMZI was optimised. For a detection height of 0-20 km, 'l' was selected as 50 cm to balance the detection of radial wind speed and backscatter ratio. The overall structure of the MLM Doppler lidar based on QMZI was designed, and detailed design parameters of the system were provided. Further simulation was conducted to evaluate the detection performance of the designed QMZI- based MLM Doppler lidar system. The simulation results showed that when using a pulse laser with a power of 17.5 W@355 nm and a telescope with an aperture of 25 cm, a detection zenith angle of 30 degrees, a vertical resolution of 26 m@0-10 km and 52 m@10-20 km and a pulse accumulation time of 1 min, the radial wind speed measurement errors of the system during the day and night were less than 2.1 m/s and 2.5 m/s; the backscatter ratio relative measurement errors were less than 0.81% and 0.97%.

A novel Rayleigh Doppler lidar technology based on a quadruple dual-pass Fabry-Perot interferometer (FPI) that can accurately measure wind field, temperature and aerosol backscatter ratio from the troposphere to lower stratosphere is proposed. This study aims to analyse the detection principle of wind speed, temperature and aerosol backscatter ratio in detail and obtain their measurement error formulas. The structure of this type of lidar is studied and designed. The FPI consists of two edge channels FPI-1 and FPI-2, aerosol channel FPI-M and locking channel FPI-L. FPI-1, FPI-2 and FPI-M use a dual-pass optical path, whereas FPI-L uses a single-pass optical path. The parameters of FPI are optimised as follows: the free spectral spacing (FSR) is 12 GHz, the FWHM of FPI-1 and FPI-2 are both 2.2 GHz, the peak-to-peak interval of FPI-1 and FPI-2 is 5.8 GHz, the FWHM of FPI-M and FPI-L are both 1.2 GHz, the peak-to-peak interval of FPI-M and FPI-1 is 2.9 GHz and the peak-to-peak interval of FPI-L and FPI-1 is 2.3 GHz. Under simulated atmospheric conditions, for a daytime sky background brightness of 0.3 Wsr- 1m- 2nm- 1 at 355 nm, using a laser with a pulse energy of 350 mJ and a repetition fre-quency of 50 Hz and a telescope with a 0.45-m aperture, with a vertical range resolution of 30 m at 0-10 km, 100 m at 10-20 km and 500 m at 20-35km, temporal resolution of 30 min, zenith angle of 0 degrees for temperature and aerosol backscatter ratio detection and temporal resolution of 3 min and zenith angle of 30 degrees for radial wind speed detection, the detection performance of the designed Rayleigh Doppler lidar is determined. The simulation re-sults show that the measurement errors of aerosol backscatter ratio, temperature and radial wind speed of the lidar system in the daytime and night-time are less than 4.36 x 10-3 and 3.32 x 10-3 (excluding cirrus cloud area), 4.0 K and 3.0 K and 3.8 m/s and 1.9 m/s, respectively, from an altitude of 0.06 to 35km.

为了实现高精度连续探测对流层和平流层大气风场，搭建了一台直接测风激光雷达系统对对流层和平流层大气风场进行探测。该系统基于双边缘法布里-珀罗标准具的瑞利散射多普勒测风原理，使用转台式探测结构，通过频率跟踪的手段对频率漂移进行跟踪，确保测风的精度。实验结果表明，该系统对对流层和平流层大气风场探测效果良好，频率跟踪的范围为±50 MHz，可以大大减小频率漂移带来的风速误差。经过系统的稳定运行和长时间的观测，在40 km处测得的径向风速随机误差为8 m/s。径向风速合成为水平风速后，随机误差在38 km处最大为10 m/s左右。该系统白天探测高度为25 km，夜晚探测高度为38 km。与探空数据对比，风速误差均小于10 m/s，其中风速误差在±5 m/s的范围内的数据量约占75.8%，探测的风向误差与探空气球的趋势基本一致，误差范围在10°～20°之间，在15°范围内的数据量约占58.6%。将实测数据与探空数据进行统计分析，结果具有良好的一致性。该系统可以为对流层和平流层大气风场的探测提供数据支撑。

提出了基于双法布里-珀罗干涉仪（FPI）的多纵模米散射多普勒激光雷达技术，分析了探测原理，并导出了径向风速和后向散射比测量误差公式。该技术要求多纵模激光源的纵模间隔与双FPI的自由谱间距相匹配，并将各纵模的中心频率锁定在双FPI周期性频谱曲线的交叉点附近。详细分析了频率匹配误差引起的风速测量误差。在低风速区域，由频率匹配误差造成的风速测量误差增加的百分数E V 随匹配误差的增大而迅速增大；频率匹配误差不变时，E V 随风速增大而缓慢减小；当频率匹配误差小于10MHz时，E V 将小于5%。设定合理的大气模式和系统参数，对基于双FPI的多纵模米散射多普勒激光雷达的探测性能进行了仿真分析。结果表明：在0～10km高度、0～50m/s的径向风速范围内，当距离分辨率为30m、时间分辨率为30s、激光发射天顶角为30°时，系统白天和晚间的径向风速测量精度分别优于1.50m/s和1.02m/s；在无云条件下，系统白天和晚间的后向散射比相对测量精度分别优于6.57%和4.53%。

To provide references for the design of the lab’s upcoming prototype of the compact spaceborne lidar with a high-repetition-rate laser (CSLHRL), in this paper, the detection signal of spaceborne lidar was simulated by the measured signal of ground-based lidar, and then, the detection capability of spaceborne lidar under different atmospheric conditions was evaluated by means of the signal-to-noise ratio (SNR), volume depolarization ratio (VDR) and attenuated color ratio (ACR). Firstly, the Fernald method was used to invert the optical parameters of cloud and aerosol with the measured signal of ground-based lidar. Secondly, the effective signal of the spaceborne lidar was simulated according to the known atmospheric optical parameters and the parameters of the spaceborne lidar system. Finally, by changing the cumulative laser pulse number and atmospheric conditions, a simulation was carried out to further evaluate the detection performance of the spaceborne lidar, and some suggestions for the development of the system are given. The experimental results showed that the cloud layer and aerosol layer with an extinction coefficient above 0.3 km−1 could be easily obtained when the laser cumulative pulse number was 1000 and the vertical resolution was 15 m at night; the identification of moderate pollution aerosols and thick clouds could be easily identified in the daytime when the laser cumulative pulse number was 10,000 and the vertical resolution was 120 m.

种子注入的372 nm稳频Nd:YAG激光器作为铁共振荧光多普勒激光雷达的激光光源，其性能将直接影响大气温度和径向风速的测量精度，属于研制难度较大但极其重要的关键技术。文中对激光光源的频率稳定性进行了仿真分析和实验研究。利用蒙特卡洛方法，仿真了振荡级输出1 116 nm脉冲光的频率稳定性（均方根）应小于1 MHz；对改进型Ramp-Fire种子注入技术进行了详细介绍，并在振荡级光路中采用了该技术；通过激光拍频实验，测量得出1 116 nm脉冲光在10 min内的频率稳定性的均方根为543.24 kHz，其结果满足指标要求，可将频率抖动和频率漂移引起的系统误差减少至0.51 K和0.61 m/s。文中所做工作为铁共振荧光多普勒激光雷达实现大气温度和径向风速的高精度测量提供了必要保障。

This paper investigates the transmitter and receiver performance of an active rotating tropospheric stratospheric Doppler wind Lidar. A 532 nm laser was determined as the detection wavelength based on transmission and scattering aspects. A ten-fold Galileo beam expander consisting of spherical and aspherical mirrors was designed and produced to compress the outgoing laser’s divergence angle using ZEMAX simulation optimization and optical-mechanical mounting means. The structure and support of the 800 mm Cassegrain telescope was redesigned. Additionally, the structure of the receiver was optimized, and the size was reduced. Meanwhile, the detectors and fiber mountings were changed to improve the stability of the received optical path. A single-channel atmospheric echo signal test was used to select the best-performing photomultiplier tube (PMT). Finally, the atmospheric wind field detection results of the original and upgraded systems were compared. The results show that after optimizing the transmitter and receiver, the detection altitude of the system is increased to about 47 km, and the wind speed and wind direction profiles match better with radiosonde measurements.

提出了基于双级联法布里-珀罗干涉仪（FPI）的多纵模高光谱分辨率测温激光雷达技术。分析了该技术的温度探测原理，并据此构建温度探测的理论模型，导出了温度和后向散射比测量误差公式。该技术要求多纵模激光发射源的纵模间隔与双级联FPI的自由谱间距相匹配，并将各纵模的中心频率锁定在前级FPI周期性频谱的峰值位置。详细分析了频率匹配误差和锁定误差引起的温度测量偏差，结果表明：后向散射比越大，相同的频率匹配误差和锁定误差引起的温度测量偏差就越大；频率匹配误差对温度测量的影响大，为保证低层大气温度测量准确，频率匹配误差和锁定误差应分别小于5 MHz和10 MHz。进一步给出了采用FPI腔长粗扫和细扫相结合的频率匹配校准方法和步骤。设定合理的系统参数，对基于双级联FPI的多纵模测温激光雷达系统的探测性能进行仿真分析。结果表明：在0～20 km高度范围内，通常匹配误差和锁定误差引起的温度测量偏差很小，在2 km以上可忽略不计；若出现云层、沙尘等，对应高度的温度测量偏差将会较大；垂直距离分辨率取30 m@0～12 km和60 m@12～20 km、时间分辨率取1 min时，白天和晚间由噪声引起的温度测量误差分别小于3.7 K和3.5 K，后向散射比相对测量误差分别小于0.40%和0.38%。

激光雷达作为大气探测的有效手段之一,逐渐向小型化、轻量化的趋势发展.针对激光雷达的功能专用性,基于现场可编程门阵列(FPGA)对探测、采集系统进行了集成优化设计.逻辑中各模块之间通过握手协议和同步有限状态机有序配合完成数据链路的构建和传递.系统以FIFO作为ADC的数据存储器,通过AXI总线协议配合Xilinx MIG IP有序将FIFO的数据突发缓存到DDR中,并且通过千兆以太网完成对采集数据的传输.该激光雷达数据采集卡集成光电倍增管增益控制和回波信号采集功能,并采用兼容性硬件和逻辑设计,具有集成度高、增益调节便捷且精度高、采集快速方便以及快速适配等诸多优点.