2021年7月2日内蒙古兴安盟龙卷环流背景和雷达特征分析
Analysis of the Tornado Circulation and Radar Characteristics in Hinggan, Inner Mongolia on 2 July 2021
中文摘要：
利用常规观测、再分析资料和雷达数据等对2021年7月2日兴安盟翁根海拉苏嘎查EF3级龙卷的天气背景、环境条件、雷达特征等进行分析。结果表明：该龙卷发生在东北冷涡背景下，直接影响系统为冷涡后部下摆的横槽，处于横槽的强偏西气流中，龙卷发生在槽后干冷空气与低层浅薄湿层叠加区域，并配合强垂直风切变和强烈的垂直上升运动，促使对流风暴迅速发展；龙卷发生前环境条件不稳定，低层湿度条件较差，中低层存在明显的逆温层；临近龙卷时段，低层的相对湿度迅速增加，相当位温随高度明显减小，层结趋于不稳定，风速随高度增大，高层存在明显干区；该对流单体呈现典型超级单体风暴结构，龙卷母体风暴具有明显的有界弱回波区、钩状回波和“V”形缺口；龙卷发生前首先在低层存在气旋式旋转结构，识别到中气旋，发展成熟阶段，中气旋在中层发展最为强盛；龙卷发生前具有回波强度＞60 dBz的特征，最大反射率因子高度有持续性的增长，回波顶高度呈连续下降。
中文关键词：
龙卷，超级单体风暴，中气旋
KeyWords：
tornado, supercell storm, mesocyclone
Abstract：
Based on the conventional observation data, reanalysis data and radar data, the paper gives an analysis on the synoptic background, environmental conditions and radar characteristics of the EF3 tornado in Wenggenhailasugacha, Hinggan on 2 July 2021. The results show that the tornado occurred in the background of the northeast cold vortex. The direct impact system was the downward transverse groove behind the cold vortex. The tornado lay in a strong westerly airflow in the transverse trough, and it occurred in the overlapping area of the dry cold air behind the trough and the thin moisture layer at the lower level. The convective storm developed rapidly, fueled by the strong vertical wind shear and strong vertical upward movement. Prior to the occurrence of the tornado, the environmental conditions were unstable, accompanied with poor moisture conditions at the lower level and the obvious inversion layer in the middle and lower levels. As the tornado occurrence time approached, the relative humidity in the lower layer increased rapidly, while the equivalent potential temperature decreased significantly with height. Consequently, the stratification became unstable, and the wind speed increased with height. There was an obvious dry area in the upper level. The convection cell presented the typical structure of a supercell storm. Bounded weak echo zone, hooked echo and V-notch were identified in the primitive storm of this tornado. Before the tornado occurred, an cyclonic structure was found in the lower level, which was recognized as a mesocyclone. As it evolved and matured, it peaked in the middle level. In addition, prior to the tornado, the radar echo intensity was greater than 60 dBz, the height of maximum reflectivity factor kept growing, and the height of the echo top showed a continuous downward trend.