一次超级单体雹暴观测分析和成雹区识别研究

利用多普勒雷达资料，结合探空和常规资料，对2011 年4 月17 日一次超级单体雹暴的流场和回波结构演变特征进行了详细研究，主要结果:该雹暴是在条件性不稳定和垂直风切变较大的环境条件下产生的右移风暴。雹云初生发展阶段，垂直剖面显示逐渐形成有组织化的斜上升气流促进雹云发展。成熟降雹阶段，雹云内形成一支强的斜上升气流和深厚的中气旋，主上升气流对应雹云的弱回波区。雹云维持典型的弱回波区—悬挂回波—回波墙特征结构。根据雷达径向速度和雹云移速订正得出的“零线”演变发现，随着雹云的发展，“零线”逐渐向悬挂回波靠近，并穿过悬挂回波，“零线”的走向为上翘式，附近“穴道”的汇集力较强，有利于降雹。通过对“零线”位置的判断可分析有利成雹的区域。根据高低空两层强回波的水平错位，利用两高度强中心连线所作剖面能快速准确得出特征剖面，并将0℃ 层以上6 km 高度处降雹潜势达到100%的45 dBZ 的区域识别为成雹区，与降雹实况对比发现识别效果良好。

Observations, Analysis, and Hail-Forming Area Identification of a Supercell Hailstorm

A detailed analysis on the evolution of stream fields and echo structures of a supercell hailstorm that occurred on April 17, 2011, is conducted on the basis of Doppler radar data combined with radio sounding and surface observation. The main results are as follows: The hailstorm occurred in a conditional instability and significant vertical wind-shear environment, which belong to right-moving storms. A cross-section of the development stage shows that an organized updraft was formed gradually, which promoted the formation and development of the hail cloud. During the hail-forming stage, a strong, tilted updraft and deep mesocyclone manifested in the hailstorm; the main updraft corresponded to the weak echo region. The hailstorm maintained a typical bounded weak echo region (BWER)- overhang-echo-wall-echo structure. According to the evolution of zero velocity line, which connects the radar radial velocity and the speed of hailstorm, the line approached the overhang echo zone with hail cloud development and crossed the overhang echo. The trend of zero velocity line was upturned, and the collection power of the cave channel near the line was sufficiently strong to form hail. The hail formation area can be analyzed through the determination of the zero velocity line. A method of identifying the characteristic structure of the hail-forming region is also presented in this study. According to the strong echo dislocation of high and low levels, the characteristic structure is determined quickly and accurately from the strong echo center section at two heights. Moreover, a 45 dBZ region at a 6 km height above the 0℃ layer is identified as the hail-forming region, where the potential of hail is calculated to be 100%.The identified hail region is in contrast to the actual hail observation.