Precise Detection Of Atmospheric Aerosol Optical Parameters Using Multi-wavelength And Raman Lidar

Aerosol is an important substance that affects the Earth's environmental climate and atmospheric radiation characteristics.Its optical parameters such as extinction coefficient,backscattering coefficient and lidar ratio are very important for analyzing thee particle size,type,microphysial parameters of the aerosol in the atmosphers and studying the scattering characteristics of aerosols.Because Raman lidar has the advantages that the detection system's beam splitting structure is easy to impleiment,and optical parameters can be obtained without assuming lidar ratio,Raman lidar is used by many researchers in atmospheric detection.The thesis studies the vibration Raman scatterin laser radar detection technology.According to the characteristics of vibration Raman scattering spectrum,the Raman lidar detection technology in ultraviolet and visible light wavelengths is studied.According to th principle of detecting Raman by Raman lidar,the inversion algorithm of extinction coefficient and backscattering coefficient is studied.The influence of system noise on the inversion result,is analyzed by using the simulated noise signal.The influence of system parameter variation on the backscattering coefficient and lidar ratio is discussed.A calibration method for system,parameters suitable for low visibility detection is proposed.The muliti-wavelebgth Raman lidar of five channels,355nm,387nm,532nm,607nm and 1064nm,is designed and built.The optical parameters of the spectroscopic system are tested.The system constants of the experimental system are calibrated by the high-altitude detection signal.The system constants under different experimental conditions such as pure days,mild pollution,heavy pollution and so on are derived and used for the inversion of backscattering coefficients.The lidar system is used to conduct experimental observations on aerosols over Xi'an.According to the Raman inversion method,the aerosol backscatter coefficient profile and extinction coefficient profile of 355nm and 532nm are obtained,and the lidar ratio profile and color ratio profile are further.At the same time,the backscatter coefficient profile of 1064 nm is obtained by inversion,using the Fernald method.The lidar ratio data of the Raman lidar and the solar photometer are compared and verified to verify the reliability of the Raman detection method.The lidar system is used to detect the aerosol optical parameters under different meteorological conditions(haze,cloud,sunny),and the optical parameters are changed under different conditions.The optical parameters of atmospheric aerosols are observed during the day,and the optical parameters of the day with low altitude are obtained Using the aerosol scattering signal obtained by long-time detection,the time distribution of aerosol backscattering coefficient color ratio is plotted,and the aerosol variation process under different pollution conditions is analyzed.