基于分形理论生成了高、低相对湿度下典型形态包覆水层碳黑团聚物, 分析了大气气溶胶相对湿度与碳黑粒子等效折射率和半径之间的关系, 得出包覆水层碳黑粒子半径随相对湿度的增加而显著增大的结论。采用Coat-Mie理论验证了利用Maxwell-Garnett(MG)理论结合T矩阵(MG-T)的方法计算包覆水层碳黑粒子辐射特性的准确性, 且采用Coat-Mie理论和MG-T方法得到的计算结果吻合较好。利用MG-T方法计算了两种典型形态包覆水层碳黑团聚物红外波段的辐射特性, 结果表明, 随着相对湿度增大, 密实状团聚物的辐射特性值远大于枝节状团聚物的辐射特性值;当空气湿度大于50%时, 水层厚度的增加使得碳黑团聚物粒子半径增大, 从而两形态碳黑团聚物辐射特性值均显著增大, 碳黑粒子半径的增大是使得其团聚物辐射特性显著增大的主要因素。

According to the fractal theory, soot aggregates which have typical morphologies coated with water are generated in high and low relative humidity conditions. The relationships among relative humidity of atmospheric aerosol, equivalent refractive index and radius of soot particle are investigated. It is found that the radius of soot particle coated with water remarkably increases with the increase of relative humidity. The radiation properties of soot particles are calculated by means of Maxwell-Garnett (MG) theory and T matrix (MG-T) method, while the accuracy of the calculation results is verified by Coat-Mie theory. The calculation results of the radiation properties of soot particles calculated by MG-T method are in well agreement with that by Coat-Mie theory. The radiation properties of two kinds of soot aggregates in infrared wavelength are calculated by MG-T method. The results reveal that the values of radiation properties of packed soot aggregates are much larger than those of the branched soot aggregates with the increasing relative humidity. When the relative humidity is larger than 50%, the values of the radiation properties of the two kinds of soot aggregates increase due to the increase of water layer thickness and radius of soot aggregates. It is confirmed that the radius of soot aggregates plays a critical role in determining the radiation properties for soot aggregates.