外混合气溶胶吸湿性对其平均消光系数的影响

基于Mie散射理论与气溶胶颗粒粒径及折射率的湿度增长模型,以两种典型吸湿性气溶胶外混合组成的颗粒系为研究对象,计算分析了气溶胶平均消光系数对环境相对湿度的依赖关系。计算结果表明:在可见光与近红外波段,当相对湿度在60%~95%的范围内逐渐增大时,气溶胶颗粒物吸湿增长,使其粒度分布逐渐增宽,等效折射率逐渐减小,造成气溶胶的平均消光系数呈指数规律增长。进一步计算发现,当外混合气溶胶来源一定时,窄分布成分的气溶胶含量越高,或者某一成分的气溶胶粒度分布越窄时,随环境湿度的增大,外混合气溶胶平均消光系数的增长越快。上述方法也适用于预测复杂成分的外混合气溶胶平均消光系数与相对湿度的变化关系,从而为实际大气气溶胶光学性质和大气环境质量的研究提供理论依据。

The Effect of Hygroscopicity of External Mixed Aerosol on Average Extinction Coefficient

Based on the Mie scattering theory and the humidity growth model of the particle size and the refractive index, the external mixture of two typical hygroscopic aerosols was studied. The dependence of the average extinction coefficient of aerosols on the relative humidity was calculated and analyzed. The results indicate that the particle size distribution is gradually broadened, and the equivalent refractive index decreases linearly, resulting in an exponential growth of the average extinction coefficient of aerosols with the visible and near infrared bands, when the relative humidity is gradually increased in the range 60%-95%. Further calculations found that when the source of the mixed aerosols is determined, the higher proportion of aerosols with narrow distribution or the narrower particle size distribution of a certain composition aerosols, the faster the average extinction coefficient increases with the increase of ambient humidity. The above method is also suitable for predicting the relationship between the average extinction