Fig. 1. Introduction of LCPI. (a) Work principle of LCPI; (b) measurement results of LCPI (the particles without the red box line are spherical particles, and the particles in the red box line are ice crystal particles)

Fig. 2. Structure diagram of ring light source. (a) Front view; (b) side view

Fig. 3. Calibration device diagram

Fig. 4. Variation of lens magnification with diameter

Fig. 5. Particle size measurement results under cloudy, sunny, and night conditions

Fig. 6. Comparison of measured particle size under cloudy, sunny, and night conditions with standard particle size

Fig. 7. Size of the sampling space within 1 s of each bin

Fig. 8. Installation position of the experimental instrument

Fig. 9. Observation results of contrast experiment. (a) Visibility (V); (b) particle number density (N); (c) volumetric water content (VWC); (d) mean diameter (MD); (e) temperature (T) and relative humidity (RH); (f) wind speed (WS) and wind direction (WD)

Fig. 10. Particle distribution spectra. (a) LCPI; (b) FM-120

Fig. 11. Consistency analysis results. (a) N; (b) VWC; (c) MD