The size-dependence of the linear depolarisation ratio of mineral dust aerosols is investigated. Laboratory measurements on 131 different aerosol samples with varying size distributions and mineralogical compositions are fitted with a homogeneous spheroid model. A minimum-bias and minimum-variance fit of the data is obtained for prolate model particles with a refractive index of 1.525+0.001i and an aspect ratio of 0.87. The model error is analysed by varying the input parameters to the light-scattering computations. It is found that the scattering of the measurements about the model can mainly be explained by variation of the morphology and dielectric properties, and to a much lesser extent by variation in the geometric standard deviation of the size distribution. The modelling of the data is extended by using size-shape distributions of spheroids. The results indicate that there is some freedom in choosing the best-fit weights of the shape-distribution of spheroids, which could potentially be useful when extending the model to multiple wavelengths, or to including additional optical parameters other than depolarisation. However, it is also found that the most reasonable fits of the data are obtained by mildly aspherical prolate and oblate spheroids, which limits the freedom of adjusting the best-fit weights.

研究了矿物粉尘气溶胶线性去极化比的大小依赖性。实验室对131种具有不同尺寸分布和矿物组成的气溶胶样品进行的测量与均质球体模型拟合。对于折射率为1.525 + 0.001i，长宽比为0.87的扁长模型颗粒，获得了数据的最小偏差和最小方差拟合。通过改变光散射计算的输入参数来分析模型误差。可以发现，关于模型的测量值的散射主要可以通过形态和介电特性的变化来解释，而在较小程度上可以通过尺寸分布的几何标准偏差的变化来解释。数据的建模通过使用​​椭球的大小形状分布来扩展。结果表明，可以选择最佳的椭球形状分布权重，这在将模型扩展到多个波长或包括除偏振以外的其他光学参数时可能很有用。但是，还发现最适度的数据拟合是通过轻度非球面扁长扁球形和扁球形椭球形获得的，这限制了调整最佳拟合权重的自由。