解析一次超级单体风暴过程的维持机理

利用太原C波段多普勒天气雷达监测资料，分析了2004年7月3日山西榆次超级单体风暴的演变和结构特征，并探讨了其维持机理。结果表明：该超级单体系发生在蒙古冷涡控制的天气背景下，西北向移动的左移超级单体，其低层钩状回波位于超级单体的左前侧，两条出流边界分别位于钩状回波的西北和东南。中-强的垂直风切变和较高位置的干冷空气入侵，使下沉气流稀释严重、地面外流发展滞后和较弱；中高层入流的干冷空气辐合传播大于低层出流边界辐散传播速度，使驾御超级单体强弱和存亡的中气旋不断从环境场吸收能量，并在其内部维持-支强盛的上升气流，这些因素是该超级单体得以维持的主要原因。

Analysis and explanation of maintaining mechanism of a supercell storm

In this paper, by using the radar data monitored by Taiyuan C-Wave Band Doppler Weather Radar, the generation, evolution and structure characteristic of supercell storm formed in Yuci area, Shanxi Province on July 3, 2004 were analyzed and the maintaining mechanism of the storm was further investigated. The results indicate that the supercell formed under the large scale background that the weather was controlled by the Mongolian cold vortex. It was a moving-left supercell that migrated toward northwest, at the bottom of which the hook-shaped echo was located in the left front of the supercell. Two efflux boundaries were located in the northwest and southeast of the hook-shaped echo respectively. The moderate to strong vertical wind shear and the invasion of the dry cold air from higher position caused the downdraft to spread seriously, the ground outflow to develop laggingly and weakly. The convergent propagation of the dry cold air flowing from middle-high layer was faster than the divergent propagation of the air flowing out of underlying layer boundary, which made the meso-cyclone that dominated the intensity and life of the supercell continuously absorb energy from the environmental field and maintain a strong updraft. All of these were just the primary reasons that the supercell can maintain.