Study of linear depolarization ratios across a wide range of scattering angles for particles of diverse sizes, shapes, and complex refractive indices

• Linear depolarization ratio (LDR) strongly depends on particle microphysical properties with significant variations across different scattering angle. • LDR in the forward scattering regime is negligible due to diffraction. • LDR reaches its maximum in the side scattering regime, around 140° to 160°, often with a non-descriptive, chaotic evolution for even larger angles, as the scattering angle approaches 180 °. • An increase in the imaginary part of the complex refractive index caused a decrease in LDR, quantified by the relative skin depth, κkR. Polarimetry is a valuable technique for remote sensing of atmospheric aerosol particles, with the linear depolarization ratio (LDR) being a key parameter used to characterize particle properties. This study investigates the LDRs of various aerosol particles, including nearly spherical and irregular aluminum oxide (Al 2 O 3 ), Arizona Road Dust (AZRD), and molybdenum disulfide (MoS 2 ) particles, using both laboratory measurements conducted at a wavelength of 532 nm over a scattering angle range from 0.32° to 177.6° and theoretical model computations for spheroids and Gaussian random spheres. The results demonstrate that the LDR is strongly influenced by particle size, shape, and refractive index, with significant variations across different scattering angles. In the forward-scattering regime, LDR values are small due to scattering being dominated by diffraction, while in the side-scattering regime, LDR increases, peaking around 140° to 160°, before decreasing in the back-scattering regime. This study further explores the relationship between LDR and particle morphology, as well as the impact of the imaginary part of the complex refractive index on LDR, with results showing that higher absorption leads to lower LDRs. Overall, this study contributes to a better understanding of how LDR behaves for different particle types and scattering angles, enhancing our understanding of the optical properties of aerosol particles towards improved polarimetric remote sensing retrievals.