The Research On Data Retrieval And Experimental Study Of The Multi-longitudinal-mode High-Spectral-resolution Lidar

The impact of aerosols on Atmospheric Physics research and climate change is very important,and it is closely related to human activities.The optical properties of atmospheric aerosols are imp ortant parameters of the state of the atmosphere.The detection of the optical properties of aerosols helps human understand the dynamic process of clouds and atmosphere,and provides important ideas for weather forecasting and analysis of global climate change.High spectral resolution lidar(HSRL)can detect aerosol optical properties accurately by separating aerosol Mie scattering and atmospheric molecular Rayleigh scattering signals with a spectral discriminator.The multi longitudinal mode(MLM-HSRL)HSRL uses Mach-Zehnder interferometer(MZI)with periodic transmittance function to separate the aerosol Mie scattering and atmospheric molecular Rayleigh scattering signals excited by MLM laser,so as to establish the dual lidar equations of Mie scattering channel and Rayleigh scattering channel,which provides technical support for accurate retrieval of aerosol optical parameters.A new algorithm and error analysis model for retrieving aerosol backscattering coefficient,optical depth and extinction coefficient of MLM-HSRL based on complex degree of coherence are proposed.The simulation results show that the retrieval algorithm based on complex degree of coherence has high agreement with the original data,so that it is correct and reliable;The error of retrieval results mainly comes from the lidar system constant and the complex degree of coherence of aerosol spectral signal.The presence of aerosol layers or cloud layer considerably deteriorates the accuracy of the retrieved aerosol backscattering coefficient and optical depth,and the total absolute error of aerosol backscattering coefficient is ignored,as well as the total absolute error of optical depth can be controlled within 0.4 in the majority of the lidar data when the relative error of δ is within 20%.In this paper,the experimental system of MLM-HSRL is constructed,and the experimental observation is carried out.The simulation and experimental evaluation of lidar system constant and complex degree of coherence provide data support for the uncertainty analysis of MLM-HSRL data retrieval.The results show that the estimated system constant of the measured data in sunny day is(2.46±0.02)×1010.The uncertainty of complex degree of coherence is±0.0347.The experimental results show that the MLM-HSRL can retrieve the aerosol backscattering coefficient,optical depth and extinction coefficient profiles below 3 km in clear weather.However,in cloudy weather,the MZI can only achieve the accurate retrieval of the data under cloud because of the insufficient suppression rate of the stronger scattering signal.Continuous observation results show that the MLM-HSRL system has the ability of long-term observation of atmospheric aerosols.