In recent years, researchers have emphasized the use of fractal aggregate morphology instead of the core-shell morphology in global climate models for estimating black carbon (BC) forcing. This study confirms that fractal morphology plays an important role in reducing the overestimation of aerosol light absorption calculations in the case of an urban polluted environment. During periods of high anthropogenic BC emissions at Delhi, the particle light absorption is overestimated by 50 to 200% by assumptions of both external mixing and internal core-shell mixing. While incorporating the aggregate morphology model into light absorption simulations is beneficial in such cases, it comes with a high computational burden. To address this, we propose a metric known as morphology index (MI). This index distributes the weightage between the two extreme cases of core-shell and fractal aggregate to obtain accurate particle light absorption. Long-range transported aerosols were estimated to have an MI of 0.78, and fresh local emissions had an MI of 0.48. A BC-based aerosol classification approach was developed to determine the most relevant particle size mode for light absorption. The method is based on patterns found between the correlations of the BC mass concentrations and aerosol number concentrations at the different particles sizes (BC-size correlation spectra). BC-size correlation spectra are introduced as a concept that may be used (i) independently to understand the size-dependent heterogeneous distribution of aerosol light absorption and (ii) in conjunction with MI to accurately model the optical properties of aerosols in different BC regimes.

近年来，研究人员强调在全球气候模型中使用分形聚集形态而不是核壳形态来估计黑碳（BC）强迫。这项研究证实，在城市污染环境的情况下，分形形态在减少气溶胶光吸收计算的高估方面发挥着重要作用。在德里人为黑碳排放量较高期间，通过外部混合和内部核壳混合的假设，颗粒光吸收被高估了 50% 至 200%。虽然在这种情况下将聚集体形态模型纳入光吸收模拟是有益的，但它会带来很高的计算负担。为了解决这个问题，我们提出了一种称为形态指数（MI）的指标。该指数将权重分布在核壳和分形聚集体两种极端情况之间，以获得准确的粒子光吸收率。远距离输送的气溶胶的 MI 估计为 0.78，新鲜的本地排放物的 MI 为 0.48。开发了一种基于 BC 的气溶胶分类方法，以确定与光吸收最相关的颗粒尺寸模式。该方法基于不同颗粒尺寸下 BC 质量浓度和气溶胶数量浓度之间的相关性（BC 尺寸相关谱）。 BC 尺寸相关光谱作为一个概念引入，可用于 (i) 独立地了解气溶胶光吸收的尺寸相关异质分布，以及 (ii) 与 MI 结合准确模拟不同 BC 状态下气溶胶的光学特性。