Abstract:A rare weather event featuring a long-lived freezing rain and ice pellets transitioning to snow occurred in the southern Shandong Region from 20 to 21 February 2024. Using conventional observational data, wind-profiling radar data, raindrop spectrum data and ERA5 reanalysis data, this article analyzes this event. The results indicate as follows. The event was characterized by return-flow precipitation. A southwest warm and humid airflow ahead of the upper-level trough slid upwards along a cold pad caused by a significant temperature drop due to the low-level strong cold air. The interaction between the mid-level warm and humid airflow and the low-level northeastern airflow formed a strong inversion temperature, and the “cold-warm-cold” vertical temperature structure was maintained for a long time, leading to a 12 h period of freezing rain and ice pellet weather. Both freezing rain and ice pellets exhibited typical characteristics of ice-phase melting. The ground temperature during freezing rain was higher, the starting height of the warm layer was lower, and both the thickness and intensity of the warm layer were greater, while the thickness and intensity of the cold layer were smaller. Raindrop spectrum data show that there was no significant difference in the particle size distribution characteristics between freezing rain and ice pellets. Both had features of small particle diameter, low particle number concentration, low precipitation intensity, and high falling velocity. Their velocity curves were similar to those of rainfall. Freezing rain had slightly larger particle diameter and fewer particle number concentration than ice pellets. During the snowfall phase, the spectrum was widened, characterized by large particle diameter, high particle number concentration, high precipitation intensity, and low falling velocity.