水汽探测拉曼激光雷达的新型光谱分光系统设计与分析

提出并设计了一套新型的大气水汽和气溶胶探测用紫外域拉曼激光雷达系统, 以二向色镜和超窄带滤光片构成高效率拉曼光谱分光系统, 实现激光雷达大气回波信号中米-瑞利散射信号、 氮气和水汽的振动拉曼散射信号的精细分离和高效率提取. 利用美国标准大气的分子散射模型和实测的大气米散射信号模型, 对分光系统的米-瑞利散射信号的抑制率、大气水汽测量的信噪比和误差进行数值仿真设计. 搭建实验系统对西安地区夜间的大气水汽进行实验观测, 并利用有云天气下实测的激光雷达回波信号, 反演获得大气后向散射比和水汽混合比的相关特性, 验证了该拉曼光谱分光系统对米-瑞利信号的抑制率达到10^-7以上量级. 理论和实验结果表明, 设计的新型拉曼光谱分光系统可以在大气后向散射比为17时, 实现水汽探测误差小于15%, 满足拉曼激光雷达系统对大气水汽的高效率探测. 关键词： 拉曼激光雷达 水汽混合比 大气后向散射比

Design and analysis of new spectroscopic system of Raman lidar for detection of atmospheric water vapor

A new ultraviolet Raman lidar system is proposed and developed for detecting atmospheric water vapor and aerosol study. The combination of dichroic mirrors and narrow-band interference filters is used as high-performance spectroscopic system to obtain the fine-separation and high-efficiency extraction of Mie-Rayleigh scattering signals, the vibrational Raman scattering signal of H₂O and N₂. By the American standard model and a set of atmospheric scattering signal model, the signal-to-noise ratio (SNR) and the water vapor measurement error are simulated and analyzed. The preliminary experiments are carried out at nighttime in Xi'an area for detecting the atmospheric water vapor and aerosols. Taking a set of the atmospheric returned signals measured under cloudy weather for example, the profiles of atmospheric backscatter ratio and water vapor mixing ratio are retrieved, and the SNR profiles of the three channels are discussed and verify that this configuration can achieve a high rejection rate (10^-7) to Mie-Rayleigh scattering. The theoretical and experimental results show that water vapor detection error of less than 15% can be obtained under a backscatter ratio of 17, which demonstrates the feasibility of the system for the atmospheric aerosol and water vapor measurements.
Keywords： Raman lidar water vapor mixing ratio atmospheric backscatter ratio