Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition
Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition
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DOI：
10.1073/pnas.1919723117
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发表时间：
2020-03-10
影响因子：
11.1
通讯作者：
Wolff, Lindsay
中科院分区：
文献类型：
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作者：
Fierce, Laura;Onasch, Timothy B.;Wolff, Lindsay
黑碳（BC）吸收太阳辐射，导致强烈但不确定的气候变暖效应。模拟和量化BC对气候的辐射影响的一个关键挑战是预测BC和其他气溶胶成分之间的内部混合导致的光吸收增强。建模和实验室研究表明，BC，当与其他气溶胶成分混合，吸收更强烈的比纯的，未涂覆的BC;然而，一些环境的观察表明更多的变量和较弱的吸收增强。我们表明，低于预期的增强环境测量结果从两个因素的组合。首先，通常使用的球形同心核壳近似法通常高估了BC的吸收。其次，更重要的是，不充分考虑颗粒间组成的异质性会导致总颗粒群吸收的显著高估，异质性越大，模型测量差异越大。我们表明，占这两个效应的变化，每个粒子的组成和偏离核壳近似调和吸收增强预测与实验室和现场观测，并解决了明显的差异。此外，我们一致的模型框架为改进BC对气候的辐射影响的预测提供了一条前进的道路。
Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC's radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model-measurement differences. We show that accounting for these two effects-variability in per-particle composition and deviations from the core-shell approximation-reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC's radiative effect on climate.