2014年7月14日新乡强对流过程成因分析

Cause Analysis of Severe Convection over Xinxiang on 14 July,2014

利用常规和区域自动站观测资料、卫星和多普勒雷达监测产品及NCEP再分析资料,对2014年7月14日新乡强对流过程进行了综合分析。结果表明:高空东移冷槽与低层暖脊叠加使新乡上空形成明显的不稳定层结,而中低层暖湿空气在午后表现出明显的北抬和向高空扩展的趋势,使大气对流不稳定度进一步加强,有利于雷暴大风和冰雹强对流天气的出现;同时,强对流天气发生前0—6 km垂直风切变达到中等偏强程度,有利于对流系统的形成和维持。地面中尺度辐合线起对流触发作用,辐合线尾部前侧的对流云团发展更强更快。云团合并导致对流云团迅猛加强,对流单体合并有利于对流回波的暴发性发展及回波顶快速抬升。过程中雷暴外流边界也是强对流的重要触发机制,太行山脉东侧的雷暴外流边界受地形抬升作用,触发大范围分散的对流单体,导致了局地短时强降水天气。风灾主要是由多单体风暴中的下击暴流和雷暴外流边界造成的,下击暴流造成的大风比由雷暴外流边界导致的大风更强。此外,强回波中心强度增强、质心高度迅速升高,回波顶高和VIL值跃增等对强对流过程中局地冰雹预报有较好的指示意义。

Based on the conventional observation data, meteorological data from regional automatic weather stations,satellite data, Doppler radar data and NCEP reanalysis data, the severe convection over Xinxiang on 14 July,2014 was analyzed. The result showed that the upper eastward cold trough and the lower warm ridge overlaying attributed the strong instability of atmospheric stratification. The mid-lower warm moist atmosphere moved northward obviously and developed to upper level in the afternoon. The atmospheric convective instability was significantly enhanced, which was favorable to the occurrence of thunderstorm gale and strong convective weather. Before the severe convection occurred,the vertical wind shear from 0 km to 6 km had the moderate to strong level,which is conducive to the formation and maintenance of convective systems. The surface mesoscale convergence line activated the severe convection. The convective cloud cluster in front of the surface convergence line tail developed stronger and faster. The merge of convective cloud clusters leaded to the rapid strengthening of convective cloud clusters. The merging of convective cells benefited the growth spurt of convective echo and rapid uplift of echo top height. The thunderstorm outflow boundary was an important triggering mechanism of the severe convective weather. The thunderstorm outflow boundary uplifted by the east of Taihang Mountains triggered large-scale dispersive convective cells, which resulted in short-time strong rainfall. Gale were mainly caused by down- burst in multi-cell storm and thunderstorm outflow boundary,while the wind caused by downburst is much stronger than that caused by thunderstorm outflow boundary. The rapidly increase of echo center, center height,echo top height and VIL value had very good instruction function to the hail prediction.