Mei Liang, Kong Zheng, Ma Teng
Opt Express. 2018 Nov 26;26(24):31942-31956. doi: 10.1364/OE.26.031942.
A dual-wavelength Scheimpflug lidar system, utilizing a 4-W 808-nm and 1-W 407-nm multimode laser diodes as light sources and two CMOS sensors as detectors, is developed for the studies of the aerosol extinction coefficient and the Ångström exponent. The system performance has been successfully validated by a two-week continuous measurement campaign on a near horizontal path in May 2018 at Dalian, which is a coastal city in Northern China. The aerosol extinction coefficients retrieved by the Fernald method show good correlations with particle concentrations and relative humidities (RHs). It has been found that the enhancement factor of the backscattering coefficient at the short wavelength due to hygroscopic growth is larger than that at the long wavelength for the aerosol particles off the coast of the Yellow Sea. The Ångström exponent obtains from the aerosol extinction coefficients at the two wavelengths, varies between 0 and 2, and is found to relate with the mass concentration fraction of fine mode particles, specifically PM2.5 particles. Moreover, the Ångström exponent has a positive correlation with the RH, implying a bimodal or multimodal size distribution of aerosol particles in the measurement season.
一种双波长施密特谱线激光雷达系统被开发出来用于研究气溶胶消光系数和Ångström指数，该系统利用一个4瓦的808纳米和一个1瓦的407纳米多模激光二极管作为光源，并使用两个互补金属氧化物半导体（CMOS）传感器作为探测器。2018年5月，在中国北方沿海城市大连，该系统在一条近水平路径上进行了为期两周的连续测量活动，系统性能得到了成功验证。通过费尔纳德方法反演得到的气溶胶消光系数与颗粒物浓度和相对湿度（RHs）显示出良好的相关性。研究发现，对于黄海沿岸的气溶胶粒子，由于吸湿增长导致的短波长后向散射系数增强因子大于长波长处的增强因子。由两个波长处的气溶胶消光系数得到的Ångström指数在0到2之间变化，并且发现它与细模态粒子，特别是PM2.5粒子的质量浓度分数有关。此外，Ångström指数与相对湿度呈正相关，这意味着在测量季节气溶胶粒子具有双峰或多峰尺寸分布。
