一次冻雨积冰过程形成的微物理机制及积冰厚度数值预报研究

Microphysical mechanisms and numerical forecasting of ice accretion thickness during a freezing rain event

摘要:

利用WRF(weather research and forecasting)v3.7.1模式对2010年湖北省冬季一次冻雨积冰过程开展数值研究。研究发现,该次积冰过程中不同阶段的云微物理结构及降水形成的云物理机制相似,均通过过冷暖雨过程形成。利用由WRF模式模拟得到的积冰期间气象场及云降水微物理资料,采用积冰厚度预报模型对该次冻雨过程中积冰厚度的时间变化进行计算。与实际积冰厚度的观测结果对比发现,积冰厚度预报模型可以较好地预报该次过程中电线积冰厚度随时间的发展趋势。

Abstract:

During the winter season in southern China,freezing rain and ice accretion often lead to substantial socio-economic impacts,including power interruption,tree damage,traffic disruptions,and risk to human safety.Scientific research into freezing rain and ice accretion processes,especially their formation mechanism,is critical for improving the forecast accuracy and mitigating associated hazards.This study presents a detailed numerical investigation of the freezing rain and ice accretion event that occurred in Hubei Province in the winter of 2010.The study utilized the European Centre for Medium-range Weather Forecasts (ECMWF) ERA-Interim reanalysis dataset (0.75°×0.75° spatial resolution,6 hours temporal resolution) as the initial field,in combining with the version v3.7.1 of the weather research and forecasting (WRF) model.Results reveals that the cloud microphysical structure and precipitation formation mechanisms remains consistent across different stages of the ice accretion process,with ice accretion predominantly forming through a supercooled warm rain process.The primary growth mechanism for rainwater in the cloud is the auto-conversion of cloud water to rain and the coalescence of rain with cloud water.Notably,the coalescence of rain with supercooled cloud water plays a more significant role in increasing rainwater mixing ratios.By analyzing the meteorological field and cloud microphysical data from the WRF simulation,and integrate them with the Jones Ice Thickness Prediction Model,the study captures the temporal evolution of ice thickness during the freezing rain event.The Jones model,which utilized readily available physical quantities such as wind speed,precipitation amount,and liquid water content,effectively simulate the trend of ice thickness overtime.A comparative analysis with observed datasets confirms that the model reasonably predict the trend of ice accretion thickness during the event.Meteorological factors,such as air temperature and precipitation intensity,significantly influence ice thickness.For instance,lower air temperature accelerate ice accretion growth,while increased precipitation intensity contributes to rapid ice accumulation.The in-depth analysis of influencing factors provides a robust numerical simulation framework for improving early warnings of freezing rain and ice accretion events.Findings of this study provide a relevant analysis of the physical mechanisms,simulation outcomes,and enhance forecasting capabilities for freezing rain and ice accretion processes.Besides,the results may contribute to advancing forecast accuracy,mitigating socio-economic impacts,and bolstering disaster prevention and response strategies.