一次冰雹天气过程的潜势条件和中尺度特征分析

Potential Conditions and Mesoscale Characteristics of a Hail Process

基于常规观测资料、NCEP(1°×1°)再分析资料、FY-2G卫星云图和多普勒雷达资料等对2018年6月10日发生在甘肃省平凉市的冰雹天气过程进行分析,得出以下结论:(1)此次冰雹过程属于典型的西北气流型,高空强冷平流、冰雹发生区明显的切变线和地面辐合线以及高层气流引导地面辐合线附近生成的中尺度对流系统MCS,是造成此次强天气的主要影响系统。(2)中尺度辐合线和干线为此次冰雹天气提供了较好的触发机制;强冰雹发生区螺旋度的异常增大为雹暴系统的发展增强提供了强有力的环境场条件;强垂直风切变可促使不稳定能量释放,形成冰雹等天气,和湿斜压作用共同形成MCS发生发展的有利条件;冰雹发生区0℃层、-20℃层高度及二者之间的厚度均有利于大冰雹的形成。(3)多普勒雷达资料显示,引发强天气的回波单体附近,悬垂回波、弱回波区、钩状回波等特征明显,对应径向速度图有明显的中气旋、中层径向辐合及风暴顶辐散等特征配合,对此次冰雹等天气有很好的指示作用。

Based on conventional observation data,NCEP reanalysis data,FY-2G infrared images and Doppler radar data,a hail weather process which occurred in Pingliang of Gansu province on 10 June 2018 was analyzed.It shows that,firstly,this severe hail weather process belonged to the typical northwest airflow pattern,with strong cold advection at high altitude,the obvious shear line and surface convergence line in hail area,and mesoscale convective system MCS generated near the surface convergence line guided by the high-level airflow were the main influencing systems of this strong weather.Secondly,Mesoscale convergence line and dry line provided a proper triggering mechanism for this severe hail weather.The abnormal increase of helicity in the area where hail weather occurred provided a strong environmental condition for the development and enhancement of the hailstorm system,while strong vertical wind shear could affect the formation of hail by promoting the release of unstable energy,with wet baroclinic interaction formed the favorable condition for the occurrence and development to MCS.The height of 0℃layer,-20℃layer and the thickness between them all were beneficial to the formation of severe hail.Finally,Doppler radar data showed that near the echoes causing sever hail weather,the characteristics of suspended high strong echo,weak echo area,hook shaped echo were obvious,corresponding to the radial velocity,some characteristics of mesocyclone,mid-level radial convergence and storm top divergence were found,which had a good indicator for this hail weather.