山东半岛一次冰雹天气的雷达特征分析

Radar Characteristics Analysis of a Hailstorm in Shandong Peninsula

本文利用三部风廓线雷达资料、两部多普勒雷达资料,结合常规气象观测资料、GPS/Met资料,对2020年5月17日发生在山东潍坊、青岛地区的一次冷涡冰雹天气过程进行分析。结果表明:(1)此次冰雹过程发生在有利的环境条件中,高空为典型的“上干下湿”冰雹天气特征。山东半岛及上游地区大气可降水量在对流风暴生成前不断增大,为强对流天气发生提供了有利水汽条件。(2)利用青岛、潍坊单站风廓线雷达资料计算的温度平流、风暴相对螺旋度(SRH)能清楚地指示出强对流天气发生前,低层存在较强的暖平流,且SRH在对流风暴达到风廓线测站前持续增大。(3)利用青岛、潍坊和蓬莱三部风廓线雷达联合计算了散度、涡度。散度计算结果表明,强对流天气发生前中低层辐合不断增大,强对流天气影响期间低层辐合中高层辐散,有利于强对流风暴的发展维持;涡度计算结果表明,强对流天气发生前中低层为正涡度,而中层为负涡度。强对流天气影响期间低层为气旋式旋转辐合,高层为气旋式辐散,这有利于产生较强的上升气流,为对流风暴的维持发展提供了环境条件。(4)多普勒雷达资料分析表明,南北两个对流风暴都具备生成大冰雹的条件:深厚的回波墙、三体散射回波、较强的中气旋和较大的风暴顶辐散。北部对流风暴回波还有较为宽广的有界弱回波区并具有悬浮回波。(5)较大的垂直累积液态水含量(VIL)、较高的VIL跃增值和VIL密度有利于产生持续时间长的大冰雹。强回波主体长时间维持,有利于冰雹天气长时间持续。地面大风出现在VIL和最大反射率因子在高位维持阶段,并且多出现在VIL剧烈变化阶段。

In this paper,we use three wind profile radar data and two Doppler radar data,combined with conventional meteorological observations and GPS/Met data,to analyze a cold vortex hailstorm event that occurred in Weifang and Qingdao,Shandong Province on May 17,2020.The results show that:(1) The hailstorm event occurred in favorable environmental conditions,with typical "dry on top and wet at the bottom" hail weather characteristics at high altitude.The atmospheric precipitable water in Shandong Peninsula and its upstream area increased before the convective storm generation,providing favorable water vapor conditions for the occurrence of strong convective weather.(2) The temperature advection and storm relative helicity(SRH) calculated using wind profile radar data from single stations in Qingdao and Weifang can clearly indicate the presence of strong warm advection at low level before the occurrence of strong convective weather,and the SRH continues to increase before the convective storm reaches the wind profile observation stations.(3) The divergence and vorticity were jointly calculated using three wind profile radars in Qingdao,Weifang and Penglai.The divergence calculation results show that the mid-and low-level convergence increases continuously before the occurrence of strong convective weather.The low-level convergence and upper-level divergence is favorable to the development and maintenance of strong convective storms during its presence.The vorticity calculation results show that the low and middle layers are positive vorticity before the occurrence of strong convective weather,while the middle layers are negative vorticity.The cyclonic rotational convergence at the lower level and cyclonic divergence at the upper level during the strong convective weather are conducive to the generation of strong updrafts,which provide environmental conditions for the maintenance and development of convective storms.(4) Analysis of Doppler radar data indicates that both north and south convective storms have the conditions to generate large hail:deep echo walls,three-body scatter spikes,strong mesocyclones,and large storm top divergence.The northern convective storm echoes also have a bounded weak echoes region with overhang echoes.(5) The large vertically integrated liquid water(VIL),the high VIL value jump and the VIL density for a long time are very favorable for the generation of large hail.The main body of strong echoes is maintained for a long time,which is conducive to the long duration of hail weather.The Surface Gust occurs in VIL and the maximum reflectivity factor is in the high maintenance stage,and mostly in the violent change stage of VIL.