Study on the key parameters of icing model during the supercooled fog mixed with freezing drizzle weather

Abstract

Based on complete observations of 30 wire icing cases with the duration over 24 h at Enshi radar station, Jinsha background station, Dacaoping and Shenlongding in Shenlongjia over Hubei in the winters of 2008 to 2016, we have conducted an analysis of the effect of supercooled fog mixed with freezing drizzle on ice accretion processes, discussed distributions and influence characteristics of key simulation parameters on the basis of the icing physic model, and lastly, revealed the evolutions of simulated ice thickness of supercooled fog and freezing drizzle. The results show that the duration of icing in the mountain area is a key factor that determines the maximum ice thickness during the icing processes. The frequency of freezing drizzle is mostly concentrated in the processes of glaze, probably leading to the explosive growth of ice thickness when it occurs. The averaged growth rates of ice thickness during the freezing drizzle and no-precipitation periods are 1.26 mm·h-1 and -0.11 mm·h-1, respectively. Collision efficiency is the main parameter restraining the development of icing during supercooled-fog period, with an averaged value of 0.1 or so. Meanwhile, accretion efficiency is the main parameter restraining the development of icing during freezing-drizzle period, and its mean value is around 0.6. Supercooled-fog icing and freezing-drizzle icing show the characteristics of phased growth and continuous growth, respectively. The freezing-drizzle icing restrains the development of supercooled-fog icing.

Keywords

• freezing fog mixed with freezing drizzle
• icing model
• simulation parameter
• wire icing