Black carbon (BC) aerosols strongly absorb the solar radiation, affecting the regional and global climate through direct and indirect radiative forcing. The optical properties of BC are critical factors to estimate their radiative forcing. However, the optical absorption of BC is still under controversy partially due to the weakness in quantifying their complex morphology and mixing structures. Although a Discrete Dipole Approximation (DDA) can calculate optical properties of fine particles with arbitrary shapes, an appropriate definition of realistic BC shape models for optical simulation is essentially required. Here we present a novel Electron‐Microscope‐to‐BC‐Simulation (EMBS) tool to construct realistic BC shape models with various morphology and mixing structures for optical calculation using DDA. The optical properties of BC particles with different particle morphology, coating thickness, and embedded fraction (F) are estimated based on electron microscope. We find that absorption enhancement (E_abs) of the realistic irregular model is larger than that of the present commonly used spherical model (i.e., BC aggregate with spherical coating). The BC core morphology greatly influences E_abs of the embedded BC particles with irregular coating when the volume‐equivalent‐diameter ratio of particle to core (D_p/D_c) is larger than 1.8. The F significantly influences E_abs of BC particles, suggesting that the mixing structure between coating and core is an important factor to determine the optical absorption of aged BC particles. The study highlights that the BC core morphology, coating shape, coating thickness, and mixing structures influence their optical properties and should be considered as important variables in climate models.

中文翻译：

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黑碳颗粒的形状和混合结构的构建及其在光学计算中的应用

黑炭（BC）气溶胶强烈吸收太阳辐射，通过直接和间接辐射强迫影响区域和全球气候。BC的光学性质是估计其辐射强迫的关键因素。然而，由于定量其复杂的形态和混合结构方面的弱点，BC的光吸收仍然存在争议。尽管离散偶极近似（DDA）可以计算具有任意形状的细颗粒的光学性质，但实际上需要为光学模拟适当定义实际的BC形状模型。在这里，我们介绍了一种新颖的电子显微镜到BC模拟（EMBS）工具，可以构建具有各种形态和混合结构的逼真的BC形状模型，以便使用DDA进行光学计算。基于电子显微镜评估了具有不同颗粒形态，涂层厚度和包埋率（F）的BC颗粒的光学性质。我们发现吸收增强（E现实的不规则模型的_abs）大于当前常用的球形模型（即BC球体涂层）。当颗粒与核的体积当量直径比（D _p / D _c）大于1.8时，BC核的形态会极大地影响具有不规则涂层的嵌入式BC颗粒的E _abs。F显着影响E _absBC颗粒的含量，表明涂层和核之间的混合结构是确定老化BC颗粒的光吸收的重要因素。该研究强调，BC核心的形态，涂层的形状，涂层的厚度和混合结构会影响其光学性能，在气候模型中应将其视为重要的变量。