基于天气形势分型的珠江三角洲强对流潜势预报方法

Methods for Predicting Convective Weather Potential in Pearl River Delta Based Weather Situation Classification

珠江三角洲出现强对流的机制有多种情况,不同天气形势下引起的强对流,其出现时各项强对流指数必然存在一定的差异。本文对强对流的触发机制进行天气形势分型(冷空气影响触发、西南暖湿气流触发、后汛期副高边缘影响,台风影响等),利用广州热带海洋研究所中尺度模式GRAPES的输出资料,计算出不同天气形势下强对流发生前1h当地各层的涉及水汽条件、不稳定能量、动力条件等强对流指数,对强对流指数阈值进行选取和验证,统计出珠江三角洲不同天气形势下短时强降水和雷雨大风出现时的强对流指数阈值,并建立相应的潜势预报系统,分别通过一次典型的雷雨大风和一次短时强降水天气过程验证,表明该系统提供的强对流分型潜势预报概率产品可以较好的指示出强对流发生的时间和位置以及强对流出现的类型,预报与实况观测比较一致。

Strong convection mechanisms of the Pearl River Delta vary in different weather conditions, and there are some differences in strong convection indexes accordingly. This paper divides the strong convection triggering mechanisms of weather patterns into four sorts： cold air influence, southwest warm moisture flow, impact on the edge of the subtropical anticyclone, and typhoon influence. Outputs of the mesoscale numerical weather prediction （NWP） model of the Guangzhou Institute of Tropic and Marine Meteorology of CMA were used to calculate the thunderstorm environment characteristics, such as water vapor, unstable energy, and dynamic conditions one hour before strong convection, which were selected to verify the convective index thresholds for Pearl River Delta under different synoptic patterns and to establish the corresponding potential forecast system. Through the verification of a typical thunderstorm process and a short-time strong rainfall case, it is proved that the strong convection potential forecast products provided by the system can indicate the occurrence time and position of strong convection and convective type, which provides a reference for forecasters.