Studies On The Water Vapor Differential Absorption Lidar Based On The Scheimpflug Principle

Water vapor is the only substance in the atmosphere that has a phase change.It plays an important role in many atmospheric physical and chemical processes.Atmospheric moisture affects aerosol and cloud formation,and its concentration and distribution vary greatly with region,season,day and night,and altitude.The detection of atmospheric water vapor concentration distribution is of great significance to meteorological and climatic research.There are two main ways to detect water vapor(humidity)concentration distribution,sampling detection and remote sensing detection.Because of the high cost of sampling detection,it is impossible to measure continuously for a long time.And the passive remote sensing detection such as microwave water vapor radiometer and Fourier infrared spectrometer can only obtain rough water vapor concentration profile.The range resolution measured by GPS and infrared hyper spectral atmospheric detector is low.As an active remote sensing detection technology,lidar has the advantages of continuous measurement and high resolution;it has been widely used in water vapor detection.There are two main types of lidar for water vapor detection: Raman lidar and differential absorption lidar(DIAL).Water vapor Raman lidar detects the Raman scattering effect of the laser generated by the atmospheric molecules,and reversely displays the water vapor concentration profile through the strength of the Raman scattering echo signal.But the Raman lidar echo signal is weak,and it is difficult to detect when the background light is strong in the daytime.DIAL technology based on the absorption spectrum of water vapor to select different wavelengths of laser detection,it compares the intensity of echo signal and inverts the water vapor concentration distribution by using differential absorption cross section Due to the features of high detection accuracy,strong echo signal and continuous detection for a long time,DIAL has an important application value in water vapor distribution detection.Currently,DIAL relies primarily on a tunable pulse light source.It realizes atmospheric echo signal detection through the flight time resolution detection principle.However,pulsed DIAL systems require a high power nanosecond scale tunable light source.The system is complex and complicated to maintain,which is a great challenge in practical application.Based on the SLidar technology and the absorption spectrum technology of the fused diode laser,this paper presents a research scheme of water vapor DIAL technology based on the shamanist imaging principlem.A water vapor DIAL experiment measurement system basedon the principle of sand imaging was developed with high power multimode 880 nm and 940 nm diode laser as the light source.It has carried out research on remote sensing detection of atmospheric water vapor distribution.This paper first introduces the function of atmospheric water vapor and the current detection technology of atmospheric water vapor(humidity),including sampling detection and remote sensing detection.And this paper discusses in detail the research status of water vapor DIAL technology and Saltzman atmospheric lidar technology at home and abroad.The second chapter introduces the basic principle of SLidar technology and water vapor DIAL technology.Then this part focuses on the basic idea and characteristics and advantages of water vapor DIAL technology based on shahler imaging principle.The third chapter mainly introduces the structure and working principle of water vapor DIAL experiment system.In this part,we use the emission spectrum of a diode laser to simulate the differential absorption spectrum of water vapor.The fourth chapter mainly introduces the experimental measurement research work of this paper.The author conducted an experimental measurement study from September to October,2019.After a series of preprocessing of the measured experimental data,she obtained the atmospheric lidar curves at on and off wavelengths.The water vapor content within the detection range can be obtained by piecewise fitting of the lidar curve.In order to verify the feasibility of the experimental system,the author obtained the atmospheric humidity data of Dalian monitoring station.By comparing the experimental results with the monitoring site results,the author found that there was a good consistency between the two.Therefore,the feasibility of the principle has been preliminarily verified in this paper.Finally,this paper summarizes the work of this paper and prospect the future research work.