甘肃省东部冰雹特征及预警指标分析

利用典型代表年份的90个冰雹个例观测资料，采用统计和数理诊断的方法对冰雹天气物理量参数进行分析，构建了甘肃省东部地区冰雹天气概念模型和冰雹预警指标。结果表明：冰雹事件在时空分布上受到天气系统和地形双重影响，冰雹天气过程分为西北气流型、低槽型和低涡型，占比分别为52%、38%和10%，在地势高、地形复杂的地区更容易产生降雹。92%的降雹出现在13—20时，5—7月占全年发生降雹概率的86%。0℃层高度越高，冰雹在降落过程中融化的越快；回波顶高越高，层结水汽越丰富；强回波顶高越高，水汽越丰富，冰雹云发展旺盛；强回波顶高越接近回波顶高时，对流发展越旺盛。通过对降雹时的最大回波强度、最大回波顶高、最大垂直累积液态水含量(VIL_max)、垂直累积液水密度(VILD)以及K指数、沙氏指数(SI)、0℃层高度、-20℃层高度等物理量进行综合分析所构建的甘肃省东部地区的冰雹预警指标体系可对13 min冰雹临近预警提供定量化的判据。

Study on Hail Characteristics and Forewarning Indicators in the East of Gansu Province

Based on the observation data of 90 hail cases in typical representative years, the strong convective weather diagnosis and physical parameters of hail weather were analyzed by using the methods of statistics and mathematical diagnosis, and the hail weather conceptual model and hail forewarning index in the east of Gansu Province were constructed. The results showed that: The temporal and spatial distribution of hail events are affected by both weather system and terrain, the northwest airflow type, low trough type and low vortex type account for 52%, 38% and 10% respectively, hail is more likely to occur in areas with high and complex terrain. 92% of hail time occurs in 13-20 hours, and 86% of hail occurs in May-July. The higher height of the 0 °C layer is the faster melting of the hail in the falling process; the higher height of the echo top is the richer of the stratification water vapor; the higher height of the strong echo top is the stronger development of the hail cloud and the richer of the water vapor; when the top height of the strong echo approaches the top height of the echo, the convection develops more vigorously. Through the comprehensive analysis of the maximum radar reflectivity, maximum echo top height, maximum vertical cumulative liquid water content (VILmax), vertical cumulative liquid water density (VILD), K index, Showalter index (SI), 0 °C layer height, -20 °C layer height during hail, the hail forewarning index system in Eastern Gansu is constructed, which can provide a quantitative criterion for 13 minutes hail approaching near warning.