Microphysical Mechanisms and Topographic Effects of Different Precipitation Phases during a Winter Freezing Event in Central China: A Case Study

<title>Abstract</title> <p>In February 2024, Hubei Province experienced a prolonged winter freezing event during which snowfall, freezing rain, and rainfall occurred simultaneously, severely impacting transportation and social operations. Using NCEP reanalysis, radiosonde, and ground observations combined with high-resolution WRF simulations and microphysical source‒sink diagnostics, this study analysed the formation mechanisms of different precipitation phases and topographic influences. The results indicate that the complex terrain of Hubei modulates the spatial distribution of precipitation types. Snowfall is dominated by ice aggregation and weak riming, whereas freezing rain forms primarily through warm-layer melting and lower-level supercooling maintenance. Rainfall originates from mid- to upper-level ice particles (snow and graupel) that melt completely in a warmer layer. Source‒sink analysis highlights the key processes of snow melting, cloud–water–rain conversion, and snow riming in the evolution of precipitation. These findings clarify the microphysical pathways through which snowfall, freezing rain, and rainfall develop during this winter storm and demonstrate the utility of high-resolution WRF simulations with source‒sink diagnostics for understanding postevent processes. The simulated microphysical evolution provides a reference case for interpreting model outputs and precipitation-phase distributions during similar freezing events over complex terrain.</p>