Abstract

According to the monitoring data of the optical and microphysical characteristics of smoke aerosol at AERONET stations during forest fires in the summer of 2019 in Alaska, the anomalous selective absorption of smoke aerosol has been detected in the visible and near-infrared spectral range from 440 to 1020 nm. With anomalous selective absorption, the imaginary part of the refractive index of smoke aerosol reached 0.315 at a wavelength of 1020 nm. A power-law approximation of the spectral dependence of the imaginary part of the refractive index with an exponent from 0.26 to 2.35 is proposed. It is shown that, for anomalous selective absorption, power-law approximations of the spectral dependences of the aerosol optical extinction and absorption depths are applicable with an Ångström exponent from 0.96 to 1.65 for the aerosol optical extinction depth and from 0.97 to –0.89 for the aerosol optical absorption depth, which reached 0.72. Single scattering albedo varied from 0.62 to 0.96. In the size distribution of smoke aerosol particles with anomalous selective absorption, the fine fraction of particles of condensation origin dominated. The similarity of the fraction of particles distinguished by anomalous selective absorption with the fraction of tar balls (TBs) detected by electron microscopy in smoke aerosol, which, apparently, arise during the condensation of terpenes and their oxygen-containing derivatives, is noted.

中文翻译：

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2019年7月至8月阿拉斯加森林火灾期间烟雾气溶胶的异常选择性吸收

摘要

根据2019年夏季阿拉斯加森林火灾期间AERONET站烟雾气溶胶光学和微物理特征的监测数据，在440至近红外光谱范围内检测到烟雾气溶胶的异常选择性吸收。 1020 纳米。具有反常选择性吸收，烟雾气溶胶的折射率虚部在1020 nm波长处达到0.315。提出了指数为 0.26 至 2.35 的折射率虚部光谱依赖性的幂律近似。结果表明，对于反常选择性吸收，气溶胶消光和吸收深度的光谱依赖性的幂律近似适用于气溶胶消光深度的 Ångström 指数为 0.96 至 1.65，气溶胶消光深度的 Ångström 指数为 0.97 至 –0.89。气溶胶光学吸收深度达到0.72。单次散射反照率从 0.62 变化到 0.96。在具有异常选择性吸收的烟雾气溶胶颗粒的尺寸分布中，凝结来源的细颗粒部分占主导地位。值得注意的是，以异常选择性吸收为特征的颗粒分数与通过电子显微镜在烟雾气溶胶中检测到的焦油球（TB）分数相似，后者显然是在萜烯及其含氧衍生物的凝结过程中产生的。