差分吸收激光雷达探测二氧化硫实验研究

二氧化硫是大气中最常见、最重要的污染物之一.差分吸收激光雷达探测二氧化硫具有高时空分辨率、高探测精度等优点.用两台Nd:YAG 激光器泵浦两台染料激光器后,通过倍频晶体得到测量大气二氧化硫所需的两个波长,它们分别是on=300.05nm 和off=301.5nm.将两束光束用几组反射镜合为一束光束,经扩束镜6 倍扩束后垂直发射进入到大气中.接收望远镜收集两个激光波长的大气后向散射信号,信号采集单元记录两个波长的后向散射回波信号的垂直高度分布.通过数据反演获得二氧化硫的高度分布.初步实验结果表明,实验期间合肥西郊董铺岛垂直高度0.3~1.6km 的二氧化硫在0~14ppb 范围内波动.最后分析并估算了该二氧化硫差分吸收激光雷达的四个主要误差来源.

Experiment study of SO2 measurement by differential absorption lidar

Sulfur dioxide (SO2) is one of the most common and important pollutant in the atmosphere. Differential absorption lidar (DIAL) measurement of SO2 has the advantages of high space-time resolution and high precision. Two laser beams, produced by two dye lasers pumped by two Nd:YAG lasers, were frequency doubled by two second-harmonic crystals, respectively. The dual wavelengths of on =300.05 nm and off=301.5 nm were selected to probe atmospheric SO2. One beam of light was achieved by merging two laser beams via several mirrors, and this laser beam was expanded sixfold with a beam expander and then transmitted vertically into the atmosphere. Backscattered radiation of both wavelengths was received by the telescope and acquired by data acquisition unit. Based on the storage data, the vertical concentration profiles of SO2 can be inversion. Preliminary result during experiment shows that SO2 concentration is roughly from 0 to 14 ppb at altitude ranging from0.3 kmto 1.6 kmover Dongpu island, west suburb of Hefei city. At last, four major measurement errors of this SO2DIAL were analyzed and estimated.