Abstract Mineral dust aerosol is present throughout the atmosphere, though the climate impact of this aerosol type is still not well known. One of many factors that contributes to this uncertainty is how water uptake alters the physical and optical character of the aerosol. A sensitive optical technique, cavity ring down spectroscopy, was used to quantify changes in the extinction cross-section with increasing relative humidity for montmorillonite, Na-rich montmorillonite, and illite aerosol. An iterative approach for converting the measured optical extinction enhancement to physical growth factor over increasing relative humidity was employed to quantify the effect of changing both size and refractive index. The method demonstrates an important application of previously retrieved effective refractive indices allowing for the determination of average particle size for the non-spherical particles from simple Mie theory calculations. The changed refractive index and particle size were used to show how these properties combine and interact to alter the distribution between scattering and absorption for the aerosol. The water uptake shifted the calculated single scattering albedo of the aerosol species more toward scattering when both optical and size changes were accounted for, as opposed to just size; limitations on these calculations are discussed. These findings demonstrate the necessity of understanding the effect of optical properties and size together, especially as many climate models do not account for water uptake properties of clay aerosol. Copyright © 2020 American Association for Aerosol Research

中文翻译：

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一种迭代方法将吸水量的消光增强转化为粘土气溶胶的物理生长因子和折射率的影响

摘要 矿物粉尘气溶胶存在于整个大气中，尽管这种气溶胶类型对气候的影响仍不为人所知。导致这种不确定性的众多因素之一是吸水量如何改变气溶胶的物理和光学特性。一种灵敏的光学技术，腔衰荡光谱，被用来量化随着蒙脱石、富钠蒙脱石和伊利石气溶胶的相对湿度增加，消光截面的变化。采用迭代方法将测量的光学消光增强转换为相对湿度增加的物理生长因子，以量化改变尺寸和折射率的影响。该方法展示了先前检索的有效折射率的重要应用，允许从简单的 Mie 理论计算确定非球形颗粒的平均粒径。改变的折射率和粒径用于显示这些特性如何结合和相互作用以改变气溶胶散射和吸收之间的分布。当同时考虑光学和尺寸变化时，吸水量将计算出的气溶胶物质的单次散射反照率更倾向于散射，而不是仅仅考虑尺寸；讨论了这些计算的限制。这些发现表明有必要同时了解光学特性和尺寸的影响，特别是因为许多气候模型没有考虑粘土气溶胶的吸水特性。