平阳县梅汛降水集中期暴雨预报指标研究

Study on Rainstorm Forecast Index during Meiyu Precipitation Concentration Period in Pingyang County

利用NCEP/NCAR 6 h再分析资料和自动气象站降水实况数据,查阅2009—2018年10年平阳县梅汛降水集中期所有雨日,从中筛选出暴雨个例,从强对流短时强降水和系统性降水入手,对物理量分别进行诊断分析,提炼预报指标。选取2017年为个例进行分析,归纳典型梅汛期易产生暴雨的高低空配置。结果表明:当700 hPa q>9.0 g/kg,850 hPa q>12 g/kg,暴雨概率大于70%,K指数在39左右、水汽通量Q在7~8 kg/(m·s)上下波动,更易产生暴雨天气。西南季风在梅雨期的建立和维持起到关键作用,其中低空急流≥12 m/s,有利于上升运动,对暴雨预报有一定指示性。强的上升运动对暴雨出现时段有良好的指示作用,上升运动越强,暴雨触发概率越高。高度层形成低层辐合高层辐散配置时,有利于暴雨产生。

By using ncep/ncar six hour reanalysis data and actual precipitation data of automatic weather station, this paper refers to all rainy days during Meiyu precipitation concentration period in Pingyang County from 2009 to 2018, and selects rainstorm cases. Starting with strong convection, shortterm strong precipitation and systematic precipitation, the physical quantities are diagnosed and analyzed respectively, and the prediction indicators are refined. Taking 2017 as an example for analysis, the high and low altitude configuration prone to rainstorm in typical Meiyu season is summarized. The results show that when 700 hPa q> 9.0 g/kg and 850 hPa>12 g/kg, the rainstorm probability is greater than 70%, the K index is about 39, and the water vapor flux Q fluctuates from 7 kg/(m·s) to 8 kg/(m·s),which is more prone to rainstorm weather.The southwest monsoon plays a key role in the establishment and maintenance of the Meiyu period, in which the low-level jet≥12 m/s is conducive to the upward movement and has a certain indication for the rainstorm forecast.The stronger the ascending motion, the higher the triggering probability of rainstorm. When the high level forms the low level convergence and high level divergence configuration, it is conducive to the occurrence of rainstorm.