一次冰雹天气多普勒雷达回波特征分析

利用常规气象资料和多普勒天气雷达资料，对2007年7月28日发生在新疆伊犁地区一次系统降水过后的强对流风暴过程进行分析。结果发现，此次对流风暴并无有利的大尺度系统配合，有发生突然、维持时间短、强度大的特点。利于出现局地对流风暴的主要因素为地表附近高温、高湿，空气中能量释放不完全等。本次降雹过程存在对流风暴，成熟时回波强度大于50dBz，相对应的速度图上有逆风区、辐合气旋式速度对以及下层辐合、上层辐散等特征。研究还发现，强回波区扩展到-20℃等温线以上，风暴顶辐散正负速度差较大，VIL持续大于50kg·m^-2，以及VIL突增等都是冰雹强度预报简单有效的参量。

Doppler Radar Echo Characteristics of a Hail Process

In this paper, the conventional meteorological data and Doppler weather radar data were used to analyze the severe convective storm after a systematic precipitation occurred in July 28, 2007 in Yili, Xinjiang. The results showed that this convective storm occurred abruptly, instantaneously and severely although there was no an advantageous circulation background. The primary favorite factors for the local convective storm were the high surface temperature, the high surface humidity and the incompletely liberated upper energy. This hail process appeared in a severe storm, whose reflectivity in mature stage was larger than 50 dBz, and there were an adverse wind area, the convergent cyclonic velocity pair, as well as lower level convergence and upper level divergence. It was also discovered that the effective parameters for forecasting hail intensity are： the strong echo area extending to above the -20 ℃ isothermal, the strong divergence with big difference between the positive and negative velocities, the persistence of 〉50 kg·m^-2 VIL, as well as the sudden increase of VIL.