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Lidar is an active remote sensing instrument, which has the characteristics of high precision and high spatial-temporal resolution. It has been widely used in the detection of atmospheric environmental parameters (aerosol, CO2, ozone, etc.) and meteorological parameters (temperature, water vapor, pressure, wind speed and direction, etc.). In recent years, atmospheric phenomena such as haze and climate change have been widely concerned by the public, and the national environmental governance and meteorological forecasting departments have an urgent demand for atmospheric observation technology. Atmospheric Lidar has been developed rapidly in China, and has achieved good research achievements. The research progress and development status of Lidar for atmospheric detection in recent years were introduced and summarized in this paper. According to the different detection objects detected by Lidars, Lidars can be classified as Mie scattering Lidar, Raman Lidar, high-spectral-resolution Lidar, differential absorption Lidar and et al. The advantages and disadvantages of all kinds of atmospheric detection Lidars and their applications in different detection objects were comprehensively introduced in this paper. Finally, the bottlenecks of Lidar technology were summarized, and the development trend of Lidar was also prospected.

Water is the only atmospheric parameter with three-phase state. An ultraviolet Raman lidar was developed for synchronous measurements for water vapor, liquid water and ice water in Xi’an University of Technology, Xi’an, China (34.233°N, 108.911°E). An accurate retrieval method on the basis of interference degree is proposed for synchronous three-phase water mixing ratio profiles. Preliminary measurements are carried out in the Laser Radar Center of Remote Sensing of Atmosphere (LRCRSA). Several representative examples are obtained and validated the performance of Raman system. Combined with atmospheric temperature profiles, the synchronous water vapor, liquid water and ice water profiling are retrieved and revealed the variation characteristics in three-phase water. The effective detection can reach up to a height of 5 km under cloudy weather, and synchronized growth in water vapor and liquid water content was obtained in cloud layers. Continuous observations are also made under haze weather condition, and the temporal and spatial evolution trend of three-phase water in clouds at 2 km altitude are successfully realized.

In order to investigate the biological aerosols in the atmosphere, we have designed an ultraviolet laser induced fluorescence lidar based on the lidar measuring principle. The fluorescence lidar employs a Nd:YAG laser of 266 nm as an excited transmitter, and examines the intensity of the received light at 400 nm for biological aerosol concentration measurements. In this work, we firstly describe the designed configuration and the simulation to estimate the measure range and the system resolution of biological aerosol concentration under certain background radiation. With a relative error of less than 10%, numerical simulations show the system is able to monitor biological aerosols within detected distances of 1.8 km and of 7.3 km in the daytime and nighttime, respectively. Simulated results demonstrate the designed fluorescence lidar is capable to identify a minimum concentration of biological aerosols at 5.0×10-5 ppb in the daytime and 1.0×10-7 ppb in the nighttime at the range of 0.1 km. We believe the ultraviolet laser induced fluorescence lidar can be spread in the field of remote sensing of biological aerosols in the atmosphere.

A portable micro-pulse polarization lidar system with 3D scanner at eye-safety level is developed,in which Nd∶YAG pulsed laser is employed as the exciting source with 2 μJ pulse energy and 1 kHz repetition rate,to detect the spherical characteristics and distribution of bottom aerosols in urban area.To ensure high accuracy detection near the earth's surface at the range from 80 m to 1000 m in the region of high-density aerosols such as northwest region,analog photoelectric detection technique is adopted.Continuous observations with scanning in zenith angle are carried out for the first time for depolarization ratio of atmospheric aerosols below 1 km in Xi′an in winter,the results of depolarization ratio scanning profiles are obtained and the effect of weather process and state of ground on depolarization ratio is analyzed.The experimental results show that,the depolarization ratio is around 0.1,where there were no sandstorms during the observations,and the depolarization ratio in certain regions is relative higher,which are occurred at the crossings of roads without greenbelts.The experimental results validate the feasibility of the system and will also provide scientific data for investigating the generation,transmission and diffusion characteristics of urban pollution particles.

A compact Mie scattering lidar system at a wavelength of 532 nm is developed to measure the optical properties of atmospheric aerosol particles and horizontal visibility.Some observations are performed and analyzed.The Fernald method is employed to retrieve the extinction coefficient of aerosol.Some continuous continual experiments are carried out for verifying the feasibility of the Mie scattering lidar at Xi'an area,and the observation results are demonstrated here by measuring the aerosol profiles of the extinction coefficient,the spatial temporal variation of atmospheric boundary layer height which are obtained within whole day at one hour interval,and the horizontal visibility which agrees with the data obtained from the local weather bureau.The observation results show that the Mie scattering lidar is capable of measuring efficiently the optical properties of atmospheric aerosol particles and horizontal visibility.

Water is the only atmospheric parameter with three-phase states. The study on distribution and variation in three-phase water is of great scientific significance for understanding cloud microphysics, cloud precipitation physics, and water circulation, especially in the fields of artificial weather process. In the Raman lidar detection technology of three-phase water, it is necessary to solve the problem of high-spectral spectroscopic technique to ensure fine extraction of the echo signal and the detection with high signal-to-noise ratio (SNR). Considering the Raman spectrum characteristics of three-phase water, the influences of filter parameters in the Raman channels on the overlapping characteristics are theoretical simulated and discussed in detail, and the SNR is investigated as well. Regarding the fact that optimal solution can be obtained for neither overlapping nor SNR at the same time, an evaluation function method based on the multi-objective programming problem is proposed to analyze the optimal filter parameters. The results show that the minimum overlapping value and the higher system SNR can be obtained when the central wavelength and bandwidth of the filters are determined to be 397.9 nm and 3.1 nm, 403 nm and 5 nm, 407.6 nm and 0.6 nm in solid water, liquid water and water vapor channel, respectively, and thus the optimal design can be realized for synchronous detection Raman spectroscopic system for three-phase water. Further simulation results show that effective detection can reach above 3.6 km in the daytime and over 4 km on sunny days under a system factor of 1800 J·mm·min for three-phase water Raman measurement in the daytime. Furthermore, the obtained overlapping values are applied to accurate retrieval theory for three-phase water profiles. The simulated profiles of atmospheric water vapor, liquid water and ice water indicate that the water vapor, liquid water and solid water content can be increased synchronously in the cloud layer, and their content, distribution characteristics and the corresponding error are also discussed. The above results validate the feasibility of highspectral spectroscopic technique for detecting the synchronous atmospheric three-phase water, and will provide technical and theoretical support for synchronous retrieval of three-phase water by Raman lidar.

Chlorophyll fluorescent information is closely related to the vital movement of a plant, so it can be used as a probe of the natural environment so as to quickly and accurately reflect the state of the environment around plants. A studying method of the plant leaves chlorophyll fluorescence image combining with remote sensing technology is presented in this paper. The system is designed and established to obtain the fluorescence image information of different plants in different states using an Nd:YAG solid-state laser as its excitation light source and an ICCD as the experimental image detector. The image information features are analyzed with pseudo-color enhancement, image synthesis using RGB color model and other methods. The results show that the fluorescence image can effectively reflect the texture, damage as well as the physiological state of a plant leaf, which can provide technical references for the further research on the impact of the change in environmental conditions by the fluorescence characteristics of plants.

In order to solve insufficiency of information content and resolution with chlorophyll fluorescence spectrometry, a method of LED-induced chlorophyll fluorescence analysis fused image processing technique is presented. Using small, long life and high-intensity blue (460nm) LED lamp for the near field detection, plants leaf fluorescence is induced actively based on the theory of active-inducing chlorophyll fluorescence. The method of extracting chlorophyll fluorescence characteristics is studied, by using spectrometer and image sensor fixed filter to obtain spectra and image information respectively. Through analyzing chlorophyll fluorescence spectra data and image data, the results indicate that fluorescence information and chlorophyll content have strong correlation. This research lays the foundation for living body real-time online measurement in situ.

Biological aerosols which could cause diseases of human beings, animals and plants, are living particles suspended in the atmosphere. Ultraviolet laser induced fluorescence has been developed as a standard technique used to discriminate between biological and non-biological particles. As an effective tool of remote sensing, fluorescence lidar is capable of detecting concentration of biological aerosols with high spatial and temporal resolutions. Intrinsic fluorescence, one of the most important characteristics of biological aerosols, has quite a large effect on the performances of fluorescence lidar. To investigate the effects of intrinsic fluorescence on biological aerosols, we design an ultraviolet laser induced fluorescence lidar at an excited wavelength of 266 nm, with a repetition rate of 10 Hz. Fluorescence signals are collected by a Cassegrain telescope with a diameter of 254 mm, in which fluorescence spectra of 300-800 nm are mainly considered. A spectrograph and a multichannel photomultiplier tube (PMT) array detector are employed to achieve the fine separation and highefficiency detection of fluorescence signals. According to the present configuration, we perform a series of simulations to estimate the measurement range and the concentration resolution of biological aerosols, with a certain pulse energy. With a relative error less than 10%, theoretical analysis shows that designed fluorescence lidar is able to detect the biological aerosols within a range of 1.5 km at a concentration of 1000 particles·L-1. When the detection distance enlarges to 2.1 km, detectable wavelength range is limited to 300-310 nm. In addition, the lidar is capable of identifying minimum concentrations of biological aerosols with 2 particles·L-1 and 4 particles·L-1 at fluorescence wavelengths of 350 nm and 600 nm, respectively, where the induced pulse energy is set to be 60 mJ and detected range 0.1 km. With setting energies of 40 mJ and 20 mJ, minimum concentrations of biological aerosols decrease to 3 particles·L-1 and 6 particles·L-1, respectively, at a fluorescence wavelength of 350 nm. The relative error of minimum concentration resolution is about 2 particles·L-1, increasing rapidly with range. For a fluorescence wavelength of 600 nm, both the minimum concentration and the relative error show relatively high values, 5 particles·L-1 at 40 mJ and 10 particles·L-1 at 20 mJ, where the relative errors are found to be 2 particles·L-1 and 4 particles·L-1, respectively. The results prove that a shorter intrinsic fluorescence wavelength has a better effect on biological aerosol measurement. We believe that a proper intrinsic fluorescence wavelength will further improve the detection accuracy of biological aerosols.

In order to measure the oil pollution on water surface, a fluorescence lidar model system based on laser induced fluorescence is put forward for detecting oil slick. The system model and fluorescence detecting principle are described in detail. According to the properties of detected material, wavelength of laser and filter of receiving system are adopted to ensure that the lidar system is operated at the peak wavelength. Following the development trend of miniaturization in the world, using single laser and intensified charge-coupled devices, a small fluorescence detecting system is designed. FTSS 350-50 laser made by CRYLAS company, with compact dimension, low weight and excellent energy efficiency, and PI-MAX4 intensified charge-couple devices made by Princeton Instruments company, with good time resolution characteristic, are selected to produce laser as a launch device and to inspect fluorescence lifetime and capture image as a receiving device, respectively. The laser excitation wavelength, the energy of laser, the center wavelength and bandwidth of filter, the received echo fluorescence signals, the detected concentration and distance are discussed in detail by means of the instance for oil on water surface. Through analyzing the relationship between the energy of laser single pulse and the detection concentration and by combining with the parameters of fluorescence lidar system and fluorescence lidar equation, the detecting ability of system model, signal-to-noise ratio, etc. are simulated particularly. A numerical simulation of the signal-to-noise ratio of the fluorescence particles is conducted particularly so that the detectable capacity of system designed could be described better. The results show that the signal-noise ratio of system which is operated during the night is superior to in daytime in the same single pulse energy case and that the detected range becomes gradually longer as the energy of laser improves with the same signal-noise ratio case. The required single pulse energy to support system is calculated, and further verifies the feasibility of the lidar system. The test results of the sample show that in the daytime, the design of fluorescence lidar model, with a Nd:YAG laser of 50 J single pulse energy and 355 nm wavelength serving as an excitation light source, with a collection device placed at a distance of 7 m, can satisfy the requirements for detecting oil pollution on the water surface in laboratory, and its signal-noise ratio can reach 10. In view of the actual surface fluorescence lidar detection requirements, the method of increasing the laser power is proposed. A real system with 50 mJ single pulse energy at a distance of 230 m has nearly the same performance as the laboratory lidar system, which could provide a valuable guidance for designing a real system.

The lidar observations of aerosols under near range condition are distorted because of insufficient overlapping between the transmitting laser beam and the field of view of receiving telescope in non-coaxial lidar especially in multiwavelength lidar. However, the near-range atmosphere is closely related with human’s activity. So it is important to correct the near-range signal of multiwavelength lidar. This paper presents a novel method of correcting the near-range optical parameter of multiwavelength lidar based on aerosol particle size distribution measurements and Mie scattering theory. The near-range aerosol extinction profiles on fine day, cloudy day and foggy day are corrected. The results show that the method is convenient and feasible compared with the traditional methods. This method reduces the uncertainty of inversion and correction because the wavelength dependences of lidar ratio and the weather correlation of aerosol size distribution are taken into account. This method realizes the direct correction to near-range optical parameter of multiwavelength lidar. It is favorable and convenient to study physical and optical properties of boundary layer atmosphere by using this method. It will have a broad application and prospect.