Data Processing And Error Analysis Of Differential Absorption Lidar For CO₂ Column Concentration Measurements

Differential absorption lidar(DIAL)system is an important means to detect atmospheric carbon dioxide concentration,which has great significance for monitoring the spatial and temporal distribution of greenhouse gases.In this thesis,the differential absorption lidar system is studied to obtain real-time and high-precision atmospheric carbon dioxide column concentration,and the integrated system provides the basis for the next airborne experimental detection.Firstly,the research status of differential absorption lidar system for detecting atmospheric carbon dioxide at home and abroad is introduced.The basic principles of differential absorption lidar for detecting atmospheric carbon dioxide column concentration are expounded,including the interaction mechanism between laser and atmosphere,differential absorption lidar equation,phase ranging principle and linear frequency modulation(LFM)ranging principle.For the system scheme,the system block diagram and software design flow chart of the differential absorption lidar system are given.This thesis focuses on the key techniques of resolved differential system lidar.The main research contents are as follows: 1)the parameter selection and basis of the differential laser wavelength in the system;2)the principle and parameter selection and basis of sinusoidal wave modulation method and chirped wave modulation method;3)data processing method research,including window function selection and spectrum correction algorithm;4)system error;The analysis includes quantitative error analysis,error transfer principle analysis,cumulative average analysis and atmospheric impact factor analysis.At the end of the thesis,the experimental verification of each unit of the system is carried out,including link experiment,ranging experiment,field experiment and comparative experiment.Finally,a stable and reliable differential absorption lidar system for carbon dioxide column concentration measurements was built,and experimental observations were carried out in Shanghai and Beijing for several days.Reliable trend data of carbon dioxide column concentration verified by in situ sensor were obtained.The innovation of this thesis is to develop the first domestic differential absorption lidar system which can switch sinusoidal and chirped wave modulation.The system can be used to continuously and steadily monitor the column concentration of atmospheric carbon dioxide and to measure the range of hard targets.The results of continuous multi-day observation of carbon dioxide column concentration in horizontal direction in Beijing area are first obtained.