Fig. 1. Coaxial DH system for ice crystal observation and identification

Fig. 2. Schematic diagram of cloud chamber operation

Fig. 3. Formation and dissipation of ice crystals. (a), (b) Process of increasing ice crystals; (c) process of ice crystals reduction

Fig. 4. Flow chart of microphysical parameter acquisition algorithm for ice crystal particles

Fig. 5. Method of global digital image fusion

Fig. 6. Local Tenengrad variance and determine focus of particles. (a-1), (b-1), (c-1) 35 reproduction planes; (a-2), (b-2), (c-2) curves of local Tenengrad variance of particles; (a-3), (b-3), (c-3) clear imaging positions

Fig. 7. Identification of ice crystals and droplets. (a-1), (a-2), (a-3) Identification of different ice crystals; (b-1), (b-2), (b-3) identification of different droplets

Fig. 8. Roundness curves of ice crystal particles and droplet particles

Fig. 9. Morphological analysis of ice crystal particles. (a-1), (b-1), (c-1) Original holograms of particles; (a-2), (b-2), (c-2) clear imaging positions of particles; (a-3), (b-3), (c-3) identification of particles; (a-4), (b-4), (c-4) contour extraction of particles; (a-5), (b-5), (c-5) convex hull extraction of particles; (a-6), (b-6), (c-6) extraction of smallest external rectangle of a particle

Fig. 10. Motion holograms of ice crystal particles. (a-1)-(a-4) Motion hologram of first ice crystal particle; (b-1)-(b-4) motion hologram of second ice crystal particle

Fig. 11. Three-dimensional motion trajectories of ice crystal particles