大气水汽探测地基差分吸收激光雷达系统设计与性能仿真

为持续获得对流层低层高精度、高时空分辨率的水汽浓度分布数据,提出了一套改进的大气水汽探测地基差分吸收激光雷达系统方案.详细描述了系统主要组成部分,对主要误差进行了分析与估计,并提出了一种差分吸收截面实时测量装置用于补偿发射激光器带来的测量误差.针对该系统,并结合上海地区不同季节的水汽浓度状况,对935 nm水汽吸收带中四个水汽吸收峰的差分光学厚度、雪崩二极管的倍增系数M与回波信噪比的关系、水汽浓度随机测量误差等进行了详细的仿真与分析.仿真结果表明,根据不同的季节和天气状况,可以选择不同的吸收峰以达到最佳探测效果;在300—5000 m高度范围内,最大可以达到300 m的垂直分辨率与5 min的时间分辨率,水汽浓度随机测量误差不超过18%.

System design and performance simulation of ground-based differential absorption lidar for water-vapor measurements

In order to obtain water-vapor profiles in the lower troposphere with a high accuracy and a temporal-spatial resolution, an improved ground-based differential absorption lidar system for water-vapor measurements is demonstrated. The key components of the system and the errors possibly existing in the system are described in detail. A real-time differential absorption cross-section measurement device that can compensate for measuring error caused by laser transmitter is presented. Combined with the water-vapor concentrations of different seasons in Shanghai, the differential optical thickness, the relationship between the gain of avalanche photo-diodes and the signal to noise ratio of received signal, and the statistical error in detection of four absorption lines in the 935 nm H₂O absorption band are simulated in detail. The result shows that a particular absorption line can be selected, which depends on season and meteorological condition, to achieve the best outcome. With a time resolution of 5 min and a vertical resolution of 300 m, the statistical error of water vapor concentration is no more than 18% in a range of 300-5000 m.
Keywords： differential absorption lidar differential absorption cross-section performance simulation wavelength selection