六盘山一次灾害性冰雹天气过程分析

Analysis of a Disastrous Hail Weather Process in the Liupan Mountains

利用三维风速仪、激光云高仪、Ka波段云雷达、X波段双偏振雷达和微雨雷达等特种仪器的观测资料,对六盘山区2021年7月12日一次冰雹灾害性天气过程进行分析。结合同期大气环流形势和地面气象资料,采用统计法分析了该天气过程的大气环流形势、动力场及微物理特征,并比较了山顶山脚降水粒子的差异。结果表明:此次冰雹过程中冰雹单体生命史接近1 h,降水回波从生成到消散持续时间约为2.5 h;此次降雹过程20 min内伴随大风与降温,发生位置在六盘山脉的东坡,降雹过程主要是由于地形作用导致的;降雹发生前15 min开始出现3层云,云系发展较旺盛,云层厚度较厚(约2 km),且降雹过程云底高度变化速度较快;降雹发生前20 min云体内回波有跃增现象,从初生对流到降雹结束,整个过程回波维持时间较长,移动方向为西北—东南,组合反射率最大值达52.5 dBZ。

Using specialized observation equipment such as three-dimensional anemometers,laser ceilometers,Ka-band cloud radars,X-band dual-polarization radars,and micro rain radars,the hailstorm weather event that occurred in the Liupan Mountains on July 12,2021,was analyzed.Combined with the atmospheric circulation situation at the time and surface meteorological data,statistical methods were used to analyze the atmospheric circulation,dynamic field,and microphysical characteristics of the weather event,and differences in precipitation particles between the mountain summit and base were compared.The results show that the lifespan of individual hail cells during this event was close to 1 hour,with the precipitation echo lasting from formation to dissipation for about 2.5 hours.The hail event was accompanied by strong winds and a drop in temperature within 20 minutes of its occurrence,with the location on the eastern slope of the Liupan Mountains,and was mainly due to topographical effects.Fifteen minutes before the onset of hail,three cloud layers began to appear,with vigorous cloud development and a thick cloud layer(about 2 km),and the cloud base height changed rapidly during the hail event.Twenty minutes before the hail began,there was a sudden increase in radar echo within the cloud body.From the initial convection to the end of the hail,the echo lasted for an extended period,with the movement direction from northwest to southeast,and the maximum composite reflectivity reaching 52.5 dBZ.