Study On High Resolution Differential Absorption Lidar And All-Time Water Vapor Profiling

Water vapor is an important component of the atmosphere and it is closely related to climate change.Water vapor participates in and affects many atmospheric physical and chemical processes.The highly reliable measurement of the temporal and spatial distribution of atmospheric water vapor concentration is very helpful for understanding global circulation,hydrological cycle,storm phenomena,boundary layer structure and dynamics,and atmospheric radiation transmission.Due to the limitations of various detection methods,the atmosphere water vapor concentration profile obtained by the current conventional measurement methods have a common problem of insufficient resolution or precision.In recent years,the progressive development of active remote sensing technology has provided a new idea for atmosphere water vapor detection.Especially,differential absorption lidar has become the only remote sensing technology that can have advantages both in resolution,accuracy and signal-to-noise ratio.There are many classic cases in the world that apply this technology to water vapor detection.This paper reports a specially made 936 nm wavelength tunable ground-based differential absorption lidar system developed by the Key Laboratory of Space Active Opto-electronics Technology of Chinese Academy of Sciences.The full text is divided into six chapters,and the detailed contents for each chapter are as follows.The first chapter introduces the significance and existing methods of atmosphere water vapor detection,and discusses the irreplaceable advantages of differential absorption lidar in atmosphere water vapor detection,which provides a background for this research.After that,the development history of differential absorption lidar and the worldwide research status are reviewed.A set of typical water vapor detection differential absorption lidar systems are introduced.Chapters 2 to 5 are the core content of this dissertation,which mainly includes the following three parts:1)Detailed theoretical derivation;Chapter 2 analyzes the principle of differential absorption lidar detection technology,evaluates various factors causing water vapor detection error and its contribution to error,and calculates the system parameter conditions that need to be met for high-precision detection.These derivations have provided sufficient theoretical support for this dissertation;2)Development of differential absorption lidar system;In Chapter 3,the design ideas and implementation methods of single longitudinal-mode transmitter,dual channel receiver and specialized client software are pressented in detail.The selfdeveloped ultra-high precision seed-laser frequency stabilization system and optical parametric oscillator cavity controller are mainly described.Chapter 4 shows the implementation of Python-based data processing algorithms.These chapters are the core innovations of this study;3)A large number of observation experiments of water vapor concentration in Shanghai Hongkou District are shown in Chapter 5;These experiments prove that our lidar system can accurately measure the atmosphere water vapor concentration in the range of 250 m to 3000 m from the ground when the time resolution is 60 s and the range resolution is 60 m.The comparison with the radiosounding data of the weather station at a specific moment proves the effectiveness of the system;when the time resolution is 10 s and the range resolution is 60 m,the boundary layer turbulence parameters can be detected,which further proves the superiority of the system.Chapter 6 is a summary and outlook,summarizing the work of this paper,including the research priorities,application prospects,innovations and deficiencies.