With the advantages of fine temporal-spatial resolution, lidar has become a powerful tool for atmospheric monitoring. Atmospheric lidars can be classified due to the detection technology as Mie lidar, polarization lidar, Raman lidar, differential absorption lidar(DIAL), high spectral resolution lidar(HSRL), Rayleigh lidar, resonance fluorescence lidar and Doppler lidar. The principle of various lidars for detection of atmospheric aerosol and clouds, water vapor, temperature, wind, trace gases, greenhouse gases and pollution gases is described elaborately. The advantage and disadvantage of each technology is summarized, as well as development history and the trend of the lidar technology for atmosphere monitoring are also explored.

The infrared spectrum of water vapor is made up of strongly absorbing bands and many transparent windows between these bands. The water vapour continuum in these same spectral regions is of particular importance for the Earth’s radiation budget and for remote sensing techniques that exploit these windows. Historically, most attention has focused on the mid-infrared atmospheric window, but there have been many fewer reports within bands and in the near-infrared spectral region. In addition, the causes of the continuum remain a subject of controversy. The history and recent developments of the causes of the continuum and calculation models were reviewed briefly. The advantages and disadvantages of several experimental methods were discussed. The possible future directions were given.

Organic acid have been widely identified as common components in atmospheric particulate matter, which is important for the investigation of atmospheric aerosol nucleation mechanism. Experimental results show that organic acids can promote the growth of sulfuric acid-water clusters. The theoretical calculations also show that the interaction of organic acids with sulfuric acid through hydrogen bonds in the presence of organic acids forms heterogeneous clusters, which can promote the formation of clusters by reducing the nucleation barriers to strengthen the formation of new particles. The influence of organic acids on the nucleation process of aerosols is reviewed, and a prospect for the development is given.

The monitoring of wind speed is very important in meteorological prediction, safety protection of aircraft and the investigation of wind resources. The 1.55 μm narrow line width all-fiber lidar is used for all optical fiber laser coherent Doppler wind technology research. A set of the motor driven wheel rotation to simulate wind speed measuring device is developed, and the scattering signal is used to produce Doppler frequency shift to calibrate accuracy of the calibration system. The single-pulse energy of the 1.55 μm all-fiber pulse laser is 10 μJ, the pulse repetition frequency is 20 kHz, the pulse width is 200 ns, and the simulated wind speed is consistent with the actual measurement results.

Ammonia sulfate, sulfuric acid, nitrate, carbon and organic carbon aerosol particle cluster are analyzed. Based on the model of cluster-cluster aggregation(CCA), the aerosol particle clusters with different compounds and shapes are simulated. Optical scattering of aerosol particle clusters is calculated by using discrete dipole approximation method (DDA). For these particle clusters, the variation of the efficiency factor with size parameters, the variation of scattering field intensity with the scattering angle and the variation of polarization degree with the scattering angle are obtained and analyzed. The calculation can be used for the analysis of the characteristics of fog haze and the light propagation in atmosphere.

In view of the limitation of inversion algorithm and the influence of thick cloud cover, MODIS aerosol products miss a lot of effective data. An ordinary Kriging-Natural proximity interpolation method based on reflectance statistical model is proposed. The response of MODIS blue band apparent reflectance to surface reflectivity and aerosol optical depth(AOD) is simulated by using 6S radiation transfer model. A statistical model of reflectivity and AOD is established. The MOD04_L2 and reflectivity data of regional aerosol products in China in November 2017 were used to carry out the experiment, and the time-space matching AERONET data was used for cross-validation. The results show that the MOD04_L2 missing data of China regions is better with this method, more than 60% of the interpolation results are within the expected error limits. The method not only effectively solves the problem of missing effective data of AOD in low reflectivity regions, but also is not affected by the improper assumption of aerosol type.

Laser sound detection technology is an important research direction in the field of voice detection, but this detection technology is vulnerable to noise interferences, which are mainly caused by background light and atmospheric turbulence. The noise suppression of detection signal is the key of laser sound detection technology. Therefore, an improved threshold function is proposed. By adjusting parameters, the deviation between the wavelet coefficients and the original wavelet coefficients can be changed, and the feature information of the original signals can be preserved as much as possible. In laboratory environment, the effectiveness of wavelet threshold denoising method based on the improved threshold function is verified by experiments. After denoising, the noise is effectively removed.

The life of solid-lubricated bearings is closely related to load. A device is developed to test the natural frequency of shaft system. The correlation between radial load which is caused by bearing pedestal misalignment and natural frequency of solid-lubricated shaft systems was researched on this test rig. The natural frequency data of shaft systems changing with radial load was analyzed. The results show that the natural frequency of shaft systems increases with the rising radial load; the correlation between radial load and natural frequency presents a power function. The radial load of solid-lubricated shaft system can be obtained by testing the natural frequency. The relative error between calculated value and experimental value of radial load is not more than 7%.