Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke
Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke
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DOI：
10.5194/acp-18-11847-2018
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发表时间：
2018-08-20
影响因子：
6.3
通讯作者：
Althausen, Dietrich
中科院分区：
文献类型：
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作者：
Haarig, Moritz;Ansmann, Albert;Althausen, Dietrich
我们介绍了加拿大西部野火烟雾的光谱分辨光学和微物理特性，这些烟雾在2017年8月22日创纪录的烟雾事件期间在对流层5-6.5公里高度和平流层15-16公里高度观察到。8月22日日落后，在德国莱比锡的欧洲气溶胶研究激光雷达网络（EARLINET）站运行了三台偏振/拉曼激光雷达。第一次，在所有三个重要的激光雷达波长355，532，和1064 nm的线性退偏振比和反射-反向散射比（激光雷达比）的老年烟雾粒子进行了测量。在对流层和平流层中发现了非常不同的粒子去极化比。对流层烟粒子结构紧凑，呈球形，在三个波长上几乎不引起后向散射光的退偏（<3%），而平流层干燥的不规则形状的烟粒子在355 nm和532 nm处的退偏率分别为22%和18%，在1064 nm处的退偏率则很低，仅为4%。对流层和平流层烟雾层的激光雷达比值分别为4045 sr（355 nm）、65-80 sr（532 nm）和80-95 sr（1064 nm），表明散射和吸收特性相似。平流层退偏比的强波长依赖性可能是由于缺少颗粒粗模（颗粒模由半径> 500 nm的颗粒组成）造成的。平流层烟雾颗粒形成了一个明显的积累模式（在颗粒体积或质量方面），集中在350-400 nm的颗粒半径。有效颗粒半径为0.32 μ m。对流层烟雾颗粒要小得多（有效半径为0.17 μ m）。2017年8月22日夜间的质量浓度约为5.5 μ g m（-3）（对流层）和40 μ g m（-3）（平流层）。平流层粒子在355、532和1064 nm处的单次散射散射系数分别为0.74、0.8和0.83。
We present spectrally resolved optical and microphysical properties of western Canadian wildfire smoke observed in a tropospheric layer from 5-6.5 km height and in a stratospheric layer from 15-16 km height during a record-breaking smoke event on 22 August 2017. Three polarization/Raman lidars were run at the European Aerosol Research Lidar Network (EARLINET) station of Leipzig, Germany, after sunset on 22 August. For the first time, the linear depolarization ratio and extinction-to-backscatter ratio (lidar ratio) of aged smoke particles were measured at all three important lidar wavelengths of 355, 532, and 1064 nm. Very different particle depolarization ratios were found in the troposphere and in the stratosphere. The obviously compact and spherical tropospheric smoke particles caused almost no depolarization of backscattered laser radiation at all three wavelengths (< 3 %), whereas the dry irregularly shaped soot particles in the stratosphere lead to high depolarization ratios of 22% at 355 nm and 18% at 532 nm and a comparably low value of 4% at 1064 nm. The lidar ratios were 4045 sr (355 nm), 65-80 sr (532 nm), and 80-95 sr (1064 nm) in both the tropospheric and stratospheric smoke layers indicating similar scattering and absorption properties. The strong wavelength dependence of the stratospheric depolarization ratio was probably caused by the absence of a particle coarse mode (particle mode consisting of particles with radius > 500 nm). The stratospheric smoke particles formed a pronounced accumulation mode (in terms of particle volume or mass) centered at a particle radius of 350-400 nm. The effective particle radius was 0.32 mu m. The tropospheric smoke particles were much smaller (effective radius of 0.17 mu m). Mass concentrations were of the order of 5.5 mu g m(-3) (tropospheric layer) and 40 mu g m(-3) (stratospheric layer) in the night of 22 August 2017. The single scattering albedo of the stratospheric particles was estimated to be 0.74, 0.8, and 0.83 at 355, 532, and 1064 nm, respectively.