一次极端暴雪事件中罕见冻雨成因分析

Analysis of the Causes of Rare Freezing Rain in an Extreme Snowstorm Event

使用常规观测、自动气象站、雷达回波及ERA5 0.25°×0.25°再分析等资料,对2021年11月8-9日发生在黑龙江省一次极端暴雪事件中罕见冻雨过程进行分析。结果表明:冻雨发生在降水强度较大时段,地面气温普遍低于0℃。垂直温度分布呈典型的“冷-暖-冷”层结特征,近地层存在强逆温层,探空温度>0℃的面积比<0℃的大。近地层冷垫是冷高压南侵时,受江淮气旋和地形阻挡,在海拔较低的松花江干流地区堆积形成。融化层在850 hPa低涡前部,西南或偏南低空急流携带暖湿空气像楔子一样插在冷空气中,持续的暖平流特征明显,地面冷垫与中层暖层之间有明显的锋区特征。电线积冰直径与融化层持续长短有很大的相关性。冻雨的形成符合“冰相融化”机制,在冻雨区具有回波强度增大的特征。

In this study,the rare freezing rain process during the extreme snowstorm event that occurred on 8-9 November 2021 in Heilongjiang province is analyzed by using conventional observations,automatic weather stations,radar echoes,and ERA50.25°×0.25°reanalysis data.The results indicate that freezing rain occurs during the periods of higher precipitation intensity,with ground temperatures generally below 0℃.The vertical temperature distribution exhibits a typical"cold-warm-cold"stratification pattern,characterized by a pronounced inversion layer in the lower atmosphere.Moreover,the region with temperatures above 0℃ surpasses that with temperatures below 0℃ in terms of spatial extent.The formation of the near-surface cold layer can be attributed to the southward-moving cold-high pressure.Hindered by the Jianghuai cyclone and local terrain,this cold air amasses in the lower elevations along the main channel of the Songhua River.The melting layer is positioned ahead of the 850 hPa low vortex,where a southwest or southerly low-altitude jet injects warm and moist air into the colder mass,displaying warm advection patterns.The interface between the ground-level cold layer and the mid-level warm layer exhibits marked frontal features and a strong inversion layer.The formation of freezing rain follows the mechanism of ice melting,exhibiting an increased intensity of radar echoes in the area affected by freezing rain.