Abstract. In this work, we have performed a series of numerical investigations on the mixing states of partially-coated black carbon (BC) based on the single-particle soot photometer (SP2). First, we calculated the scattering signal returned from partially-coated BC based on the SP2 measurement, and then the mixing states were determined using Mie theory, where the difference between the determined and "true" mixing states can represent the uncertainties of the SP2 measurement. We found that the SP2 measurement can provide good estimates for small, heavily coated BCs and shows better performance for fully coated BCs. However, the microphysical properties of BCs have a significant impact on the accuracy of the SP2 measurement; sometimes deviations of about -22 % to 28 % were observed for the determined particle-to-core size ratio (D_p/D_c). When considering a size distribution, the error in the effective radius is generally within about -17 % to 8.8 %. We also investigated the effects of Mie-based models using the SP2 determined and volume-mean D_p/D_c on the radiative effects of partially-coated BC. We found that both Mie models based on the volume mean and SP2 determined mixing states overestimate the absorption enhancement (E_abs) and direct radiative forcing (DRF) of BC. The Mie model based on the SP2 measurement does not necessarily provide worse estimates of radiative properties, although some errors occur in the determination of the mixing states, since the fraction of the coated core (F) in the particle scale is an important factor affecting E_abs and DRF. Sometimes the inaccurate measurements of the mixing states by SP2 would offset the influence of F. Moreover, our results based on the Mie model considering F can significantly improve the estimates for the absorption and DRF of partially-coated BC, although the morphology also has some influence. Therefore, we suggest adding a parameter F to model the radiative effect of BC in climate modeling even when a Mie-based model is used.

中文翻译：

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技术说明：基于单颗粒烟灰光度计的部分涂覆炭黑混合状态的数值量化：对全球辐射强迫的影响

摘要。在这项工作中，我们基于单颗粒烟灰光度计（SP2）对部分涂层黑碳（BC）的混合状态进行了一系列数值研究。首先，我们根据 SP2 测量计算从部分涂覆的 BC 返回的散射信号，然后使用 Mie 理论确定混合状态，其中确定的混合状态与“真实”混合状态之间的差异可以代表 SP2 测量的不确定性。我们发现 SP2 测量可以为小型、厚涂层的 BC 提供良好的估计，并且对于全涂层的 BC 表现出更好的性能。然而，BC的微物理性质对SP2测量的准确性有显着影响；有时观察到确定的颗粒与核心尺寸比 (D _p /D _c ) 的偏差约为 -22 % 至 28 %。当考虑尺寸分布时，有效半径的误差通常在约-17%至8.8%之间。我们还使用确定的 SP2 和体积平均 D _p /D _c研究了基于 Mie 的模型对部分涂层 BC 辐射效应的影响。我们发现基于体积均值和 SP2 确定的混合状态的 Mie 模型都高估了 BC 的吸收增强 (E _abs ) 和直接辐射强迫 (DRF)。基于 SP2 测量的 Mie 模型不一定会提供更差的辐射特性估计，尽管在确定混合状态时会出现一些错误，因为颗粒尺度中涂层核心 (F) 的分数是影响 E 的重要因素_腹肌和 DRF。有时，SP2 对混合状态的不准确测量会抵消 F 的影响。此外，我们基于考虑 F 的 Mie 模型的结果可以显着改善对部分涂层 BC 的吸收和 DRF 的估计，尽管形态也有一些影响影响。因此，即使使用基于 Mie 的模型，我们建议在气候建模中添加参数 F 来模拟 BC 的辐射效应。