Objective The study of laser transmission and scattering in ice crystal particle clouds is an important component of studying the scattering characteristics of complex systems and stochastic media. When the laser signal is transmitted within the cloud layer and interacts with ice crystal particles, it leads to energy loss, resulting in a decrease in the signal-to-noise ratio at the receiving point, sometimes even below the receiving threshold; On the other hand, it may cause some or all of the light spot to drift outside the receiver aperture, resulting in reception errors. In the field of remote sensing engineering, the physical characteristics of targets are often inverted by reflected waves. Due to the presence of clouds, ice crystal particles, and water droplet particles, the atmospheric refractive index undergoes small fluctuations. When laser passes through it, the intensity of the light field is affected, which can also cause significant inversion errors. This greatly interferes with and hinders free space optical communication and LiDAR detection. In addition, the generation mechanism of ice crystal particles in high-altitude clouds is very complex, not only with complex structures and shapes, but also with motion randomness (i.e. different spatial positions). It is necessary to consider the spatial orientation of particles in simulation calculations.

Methods The scattering parameters of individual nucleated particles and aggregated particles in this article are simulated and calculated using DDSCAT software. The calculation objects can be isolated entities , or a collection of "object units" in one-dimensional or two-dimensional periodic arrays, and can even be used to study the absorption and scattering around the smallest nanoscale structure array. DDA approximates objects through a set of polarization points. Draine and Flatau implemented the application of DDA theory in DDSCAT in 1994 and conducted effective near-field calculations in 2012. DDSCAT 7.3 can establish dipole arrays of various geometric shapes (although the dipoles must be located on a cubic lattice), the incident plane wave can have any elliptical polarization, and the object can be oriented arbitrarily relative to the incident radiation. DDSCAT can be used to calculate absorption efficiency, scattering efficiency, and extinction efficiency. It can also calculate the scattering matrix element S_ij to characterize the scattering characteristics of any spatially oriented object.

Results and Discussions Figure 1-Figure 3 take into account the different particle shapes, resulting in different scattering cross-sections. Therefore, the shape of ice crystal particles is an important factor affecting extinction efficiency, absorption efficiency, scattering efficiency, and phase matrix element light scattering; Figure 4 shows the structural models of pure and ideal tetrahedral ice crystal particles with nucleus; Figure 5-Figure 7 shows that under the condition of constant ice crystal particle size, the increase of crystal nucleus lead to the strengthening of the interaction between the inner and outer media of tetrahedral nucleated particles, and the real part of the refractive index of the crystal nucleus medium increases; Figure 9-Figure 13 establish visual orientation maps for individual particles and aggregated particles; Figure 14-Figure 19 investigates the influence of particle spatial orientation on light scattering, and then uses the least squares method to obtain the minimum value of the spatial azimuth calculated by particle simulation.

Conclusions The stronger the irregularity of ice crystal particles, the larger the effective size of the particles, and the more significant the changes in extinction, absorption, and scattering efficiency; The larger the crystal nucleus of the particle, the more pronounced the scattering directionality of ice crystal particles with nuclear structure. To study the light scattering of ice crystal particles, we cannot only study single structured particles. We should enrich the particle shapes as much as possible, consider the complex structure of particles, and improve the accuracy of simulation calculations. The maximum deviation of scattering efficiency of ice crystal particles under different spatial orientations reaches 60%. Simulation calculations must cover all directions as much as possible, but are limited by the CPU of the computer. The scattering data of tetrahedral particles in different spatial orientations were calculated in the article, and the difference between the average scattering curve of tetrahedral particles and the spatial orientation was statistically analyzed to find the minimum spatial azimuth required for tetrahedral model simulation calculation. We extended this minimum spatial azimuth to other models, providing a theoretical basis for the selection of spatial azimuth in future simulation calculations.