Cheng Tianhai, Wu Yu, Chen Hao
Opt Express. 2014 Jun 30;22(13):15904-17. doi: 10.1364/OE.22.015904.
Light absorbing carbon aerosols play a substantial role in climate change through radiative forcing, which is the dominant absorber of solar radiation. Radiative properties of light absorbing carbon aerosols are strongly dependent on the morphological factors and the mixing mechanism of black carbon with other aerosol components. This study focuses on the morphological effects on the optical properties of internally mixed light absorbing carbon aerosols using the numerically exact superposition T-matrix method. Three types aerosols with different aging status such as freshly emitted BC particles, thinly coated light absorbing carbon aerosols, heavily coated light absorbing carbon aerosols are studied. Our study showed that morphological factors change with the aging of internally mixed light absorbing carbon aerosols to result in a dramatic change in their optical properties. The absorption properties of light absorbing carbon aerosols can be enhanced approximately a factor of 2 at 0.67 um, and these enhancements depend on the morphological factors. A larger shell/core diameter ratio of volume-equivalent shell-core spheres (S/C), which indicates the degree of coating, leads to stronger absorption. The enhancement of absorption properties accompanies a greater enhancement of scattering properties, which is reflected in an increase in single scattering albedo (SSA). The enhancement of single scattering albedo due to the morphological effects can reach a factor of 3.75 at 0.67 μm. The asymmetry parameter has a similar yet smaller enhancement. Moreover, the corresponding optical properties of shell-and-core model determined by using Lorenz -Mie solutions are presented for comparison. We found that the optical properties of internally mixed light absorbing carbon aerosol can differ fundamentally from those calculated for the Mie theory shell-and-core model, particularly for thinly coated light absorbing carbon aerosols. Our studies indicate that the complex morphology of internally mixed light absorbing carbon aerosols must be explicitly considered in climate radiation balance.
吸光性碳气溶胶通过辐射强迫在气候变化中发挥着重要作用，而辐射强迫是太阳辐射的主要吸收体。吸光性碳气溶胶的辐射特性强烈依赖于形态因素以及黑碳与其他气溶胶成分的混合机制。本研究使用数值精确的叠加T矩阵方法，聚焦于内混合吸光性碳气溶胶形态对其光学特性的影响。研究了三种不同老化状态的气溶胶，如新排放的BC颗粒、薄包覆的吸光性碳气溶胶、厚包覆的吸光性碳气溶胶。我们的研究表明，随着内混合吸光性碳气溶胶的老化，形态因素发生变化，导致其光学特性发生显著改变。在0.67微米处，吸光性碳气溶胶的吸收特性可增强约2倍，且这些增强取决于形态因素。体积等效壳核球体的壳/核直径比（S/C）越大，表明包覆程度越高，吸收越强。吸收特性的增强伴随着散射特性更大程度的增强，这反映在单次散射反照率（SSA）的增加上。由于形态效应导致的单次散射反照率增强在0.67微米处可达3.75倍。不对称参数有类似但较小的增强。此外，还给出了用洛伦兹 - 米氏解确定的壳核模型的相应光学特性以供比较。我们发现，内混合吸光性碳气溶胶的光学特性可能与米氏理论壳核模型计算的特性根本不同，特别是对于薄包覆的吸光性碳气溶胶。我们的研究表明在气候辐射平衡中必须明确考虑内混合吸光性碳气溶胶的复杂形态。
