张一平,俞小鼎,吴蓁,梁俊平,吕林宜. 2012. 区域暴雨过程中两次龙卷风事件分析[J]. 气象学报, 70(5):961-973, doi:10.11676/qxxb2012.081
区域暴雨过程中两次龙卷风事件分析
Analysis of the two tornado events during a process of regional torrential rain
投稿时间:2011-01-31  修订日期:2012-03-09
DOI:10.11676/qxxb2012.081
中文关键词:  β中尺度螺旋雨带, 中气旋, 微型超级单体, 龙卷涡旋特征, 龙卷预警
英文关键词:Meso-β scale spiral rainband, Mesocyclone, Mini-supercell, TVS, Tornado early warning
基金项目:国家自然科学基金面上项目(41175043)、中国气象局预报员专项(CMAYBY2011-029)、河南省科技厅项目(112102310033)和河南省气象局项目(Z201201)
作者单位
张一平 河南省气象台郑州450003
河南省农业气象保障与应用技术重点实验室郑州450003 
俞小鼎 中国气象局气象干部培训学院北京100081 
吴蓁 河南省气象台郑州450003
河南省农业气象保障与应用技术重点实验室郑州450003 
梁俊平 河南省气象台郑州450003 
吕林宜 河南省气象台郑州450003 
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中文摘要:
      利用新一代多普勒雷达资料、常规观测和NCEP等资料对2010年7月17和19日河南两次龙卷过程进行了详细分析。结果如下:(1)龙卷发生的天气背景是:两次龙卷均发生在副热带高压边缘西南气流影响河南出现区域暴雨和大暴雨过程中,高层为青藏高压脊北侧和高空急流入口区右后侧强辐散区,中低层有低涡、切变线、急流,龙卷发生在地面β中低压气旋的东南象限,距气旋中心约50 km处。(2)龙卷发生的环境场特征:对流有效位能大于1000 J/kg,大气层结不稳定,K指数大于36℃,发生强龙卷的SWEAT指数在400左右,0—1.5 km垂直风矢量切变达15 m/s,而抬升凝结高度很低(0—300 m)。(3)雷达回波和特征参数分析结果为:两次龙卷均发生在低涡东南侧的β中尺度螺旋雨带上,该回波带强度50 dBz左右,顶高9—12 km,龙卷是由该回波带中部的微型超级单体产生,垂直剖面上低层有明显的弱回波上升气流区,螺旋雨带中部向东凸起的强降水下沉气流和上升入流交界处是龙卷易出现的关键区域。速度图上,γ中尺度气旋系列先后经历了三维相关切变、中气旋、龙卷涡旋特征的演变过程。中气旋提前于龙卷发生前0.5—1 h出现,这对估计和预警龙卷很有意义。中气旋和龙卷涡旋特征参数分析结果是:中气旋和龙卷涡旋特征(TVS)底的高度都在1 km以下,TVS底和中气旋底高度相当或略低一些,F2级龙卷底高<0.5 km,TVS顶的高度一般在2—4 km,中气旋顶高一般2—3 km;从最大切变值来看,中气旋最大切变一般在(1.0—4.0)×10-2 s-1,TVS最大切变值一般为(2.0—5.0)×10-2 s-1,最大切变高度平均出现在0.8—0.9 km,F2级龙卷最大切变高度一般在0.5 km。就F1和F2两次龙卷过程比较看,F2龙卷特征底和顶的高度都低于F1龙卷,最大切变值F2龙卷比F1龙卷大一倍,出现在低层大的切变更容易造成严重的龙卷灾害。根据局限于低层中气旋和TVS系列性、移动性、持续性的特点明确了区域暴雨中预警龙卷的思路。最后对区域暴雨过程中出现龙卷的原因进行了探讨。
英文摘要:
      A detailed analysis of the two tornado processes on 17 and 19 July 2010 in Henan was made by using a new generation of Doppler radar data, the conventional observations data, the NECP reanalysis data and other information. The results were as follows: (1)the weather background of the tornado occurrence: the two tornadoes occurred during a process of regional torrential and severe torrential rains in Henan, which were impacted by the southwestern flow in the subtropical high edge, the strong divergence areas north of the Tibetan high ridge and on the right rear of the entrance areas of the upper jet stream with the vortex, shear line and jet stream existing in the middle and lower levels.Tornadoes occurred in the southeast quadrant of mesoβcyclones on the ground, about 50 km from the cyclone center. (2) The environment field characteristics of the tornadoes covered: the convective available potential energy greater than 1000 J/kg, unstable atmospheric stratification, the K index greater than 36℃, the SWEAT index of the occurrence of strong tornadoes being about 400, the vertical wind shear for 0-1.5 km being up to 15 m/s, and a very low lifting condensation level that was from 0 to 300 m. (3) The analyzed results of the radar echo and characteristical parameters: two tornadoes both occurred in the βmeso scale spiral rainbands on the southeast side of the vortex with the intensity of the echo band of about 50 dBz and the top from 9 to 12 km, and the tornado was produced by a mini supercell that was in the center of the echo, with a significantly weak echo upward flow zone in the vertical profile and the interface zone between the rear flank downdraft and updraft is a key area which is prone to tornadoes. The γmesoscale cyclone series experinced a evolution process related to three dimensional correlated shear, mesocyclone, tornado vortex signature as shown in the velocity profiles. The mesocyclone occurred earlier about 0.5-1 h than the tornado, which made sense to estimating and warning tornado. The analyses of the mesocyclones (M) and the parameters of tornado vortex signature (TVS) show that, the height of mesocyclone and the bottom of TVS both were lower than 1 km with the height of the bottom of TVS being the same as or slightly lower than that of mesoclyclone: The height of the bottom of the F2 level tornado was < 0.5 km, the height of the top of TVS was generally from 2 to 4 km, the height of the top of mesocyclone was generally from 2 to 3 km; and from the maximum shear value, the maximum shear value of mesocyclone was generally (1.0-4.0)×10-2s-1, the maximum shear value of TVS was generally (2.0-5.0)×10-2s-1, the average height of the maximum shear appearred from 0.8 to 0.9 km, and the maximum shear height of the F2 level tornado was generally 0.5 km. On the comparison of the F1 and F2 tornadoes, the height of the characteristical bottom and top of the F2 tornado were both lower than that of the F1 tornado, and the maximum shear value of the F2 tornado was double than the F1 with the large shear in the lower level able likely to cause severe tornado disasters. According to the characteristics of the mesocyclone and the TVS, the thinking of warning the tornado in the regional torrential rainfall is illustrated. Finally, the reason of the tornadoes occurred during the regional torrential rainfall was discussed.
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