山区干环境下一次弱降水超级单体龙卷事件研究

An analysis of a low-precipitation supercell tornado event in dry mountainous environment

  • 摘要: 为增加对山区龙卷风暴的认识,应用不同波段天气雷达和风廓线等资料,分析了2023年5月14日发生在华北北部山区(围场和隆化)的2个EF1级弱龙卷,包括近风暴环境和风暴精细结构。结果表明:龙卷发生在500 hPa冷涡后部西北气流背景下,龙卷母风暴由干线及其伴随的地面辐合线触发。近风暴环境对流有效位能和0—6 km风垂直切变值大,低层水汽和0—1 km风垂直切变显著增大,有利于超级单体龙卷形成。午后热雷暴活动对山区局地水汽影响较大,是此次龙卷近风暴环境水汽增加的主要因素。产生龙卷的超级单体风暴回波强度总体不强,其中围场龙卷风暴回波强度在40 dBz以下,且强回波范围小,地面降水不足2 mm,中气旋和钩状回波头部对应旋转上升气流与降水回波分离,2个龙卷风暴均为弱降水超级单体风暴。文章记录了2个弱降水超级单体风暴的近风暴环境及精细结构演变,识别出了低层中等强度中气旋和龙卷涡旋特征(TVS),表明X波段雷达可捕捉到弱降水超级单体龙卷。围场龙卷特征的出现与龙卷发生有很好的时间对应关系,隆化龙卷发生前8 min可观测到TVS特征,此次弱降水超级单体龙卷预警时效短。

     

    Abstract: An analysis of two EF1 weak tornadoes that occurred in Weichang and Longhua including the pre-storm environmental conditions and fine structures is conducted based on observations of radars on different bands and wind profile radars. The results show that the tornado occurred under the background of northwesterly flows behind a 500 hPa cold vortex, and the parent tornado was triggered by the dry line and the ground convergence line. The supercell tornadoes occurred in the pre-storm environment with strong convective available potential energy (CAPE) and 0—6 km vertical wind shear, while water vapor at the low level and 0—1 km vertical wind shear significantly increased. The thunderstorm activity in the afternoon improved low-level moisture condition. The echo intensity of the supercell tornado was weak with that of the Weichang tornado less than 40 dBz. The areal extent was small and the precipitation near the tornado was less than 2 mm.The rotating updraft corresponding to the mesocyclone and the hook echo head were separated from the precipitation echo. The two tornados both exhibited low-precipitation (LP) supercell characteristics. In this paper, the pre-storm environment and structural evolution of the two LP supercell storms in China are recorded for the first time. Moderate mesocyclone at low levels and tornadic vortex features (TVS) were identified, indicating the X-band radar can capture the LP supercell tornado. The occurrence of the TVS corresponded well with the occurrence of the Weichang tornado, and the Longhua tornado feature was detected 8 min in advance, indicating that the warning time of the LP supercell tornado was short.

     

/

返回文章
返回