- Article
Rime accretion on transmission lines in mountainous terrain is strongly influenced by local airflow and the availability of supercooled liquid water. This study combined nested Weather Research and Forecasting (WRF) simulations, tower observations, and the Makkonen ice-accretion model to investigate a rime-icing event at Tower No. 117 in southern Hunan, China, during 1–3 January 2026. Regional analysis revealed persistent low-level cold-air advection, warm and moist airflow aloft, and a pronounced temperature inversion near the tower, indicating a cold and stably stratified environment favourable for rime formation. At the local scale, simulated airflow and model-derived liquid water content (LWC) showed patterns consistent with terrain channelling and windward-slope ascent. During both active ice-growth stages, wind speed, LWC, and a diagnostic liquid-water transport metric were higher at the tower than in a nearby reference area. During the subsequent weakening phase, air temperature remained below freezing and wind speed remained relatively high, whereas model-derived LWC and the transport metric decreased to 18.8% and 16.9% of their first-stage values, respectively. This contrast indicates that weakened rime growth was more closely associated with reduced liquid-water availability than with temperature or wind speed changes alone. The 300 m WRF configuration yielded end-of-stage ice thicknesses closer to observations than the 1.5 km configuration. Sensitivity experiments showed that quantitative ice-accretion estimates remained sensitive to model initialisation, meteorological forcing, and icing-model assumptions. Overall, the results highlight the importance of representing terrain-modulated airflow and liquid-water variability in tower-scale icing assessments over mountainous terrain.
10 November 2026





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