Analysis of the influence of system parameters on the measurement accuracy of a high spectral resolution lidar

摘要

Atmospheric aerosols play very important roles in climate change and air particulate pollution. Lidars based on elastic scattering have been widely used to measure aerosol spatial distribution and to retrieve the profiles of aerosol optical properties by an assumption of the aerosol extinction-to-backscatter ratio. High Spectral Resolution Lidar (HSRL) is one of methods that can be used to measure aerosol optical properties without a-priori hypotheses. Compared to Raman lidar, HSRL has the advantage of day and night measurements and can be adapted to many kinds of carrying platforms. Unlike ordinary elastic backscatter lidar, HSRL needs to separate the Mie signal scattered by atmospheric aerosol and the Rayleigh signal scattered by atmospheric molecules. Due to small spectral difference between Mie and Rayleigh signals, there are three difficulties: firstly, the laser source must have a narrow bandwidth, high energy and stable center wavelength; secondly, the receiver should have a very narrow spectral filter to separate aerosol scattering and molecular scattering; thirdly, the center wavelength of the receiver must be real-time locked to laser source. In order to study the influence of system parameters on the measurement accuracy of a high spectral resolution lidar and to optimize their values, a simulation and analysis has been done and will be presented in this paper. In this paper, the system parameters including the linewidth of emission laser, the bandwidth of the Fabry-Perot interferometric filter in the receiver and the spectral tracking accuracy between the receiver and laser are mainly analyzed. At the same time, several environmental factors have been considered, including atmospheric temperature and wind, pointing accuracy of platform, aerosol concentration range etc. A typical vertical distribution of atmospheric aerosol optical properties is considered and the received signals of high spectral channels are simulated. From the simulated signals, the aerosol optical properties are retrieved and the deviation relative to the input values is obtained. Under the conditions of given environmental factors, the relationship between system parameters of high spectral resolution lidar and relative error of retrieved aerosol optical properties is carried out.