Extremely Long-Duration Large-Scale Freezing Rain in Southern China and Its Link to the Persistent South Asian Jet Wave Train

Freezing rain—supercooled liquid precipitation occurring under a sandwich-like vertical temperature structure—has caused substantial damage to agriculture, transportation, and power infrastructure in southern China. Events lasting multiple days are especially damaging. This study classifies large-scale freezing rain events in southern China from 1979 to 2024 into short (S), long (L), and extremely-long (EL) categories by duration using ERA5 reanalysis data and validates the classification against station-based glaze observations. While all three categories involve southward cold surges and frontal temperature inversions, EL events are distinguished by particularly strong and persistent warm advection at 750 hPa. This sustained warm advection counteracts low-level cooling and vertical mixing, thereby maintaining the temperature inversion necessary for freezing rain. We further show that the anomalous warm advection in EL events is tightly linked to a persistent South Asian jet wave train (SAJW) pattern, which originates from precipitation reduction and Rossby wave source anomalies around the Mediterranean Sea. Our findings reveal distinct characteristics and causes of three categories of freezing-rain events, and identify persistent SAJW as a critical factor in EL events, providing insights for enhancing disaster preparedness strategies for freezing rain in southern China.