成都市短时强降水概率预报方法初探

选取2010~2019年4~9月成都市气象观测站逐小时降水资料和欧洲中心ERA-5逐小时再分析资料，采用统计分析和统计预报方法，研究了近十年成都市短时强降水时空分布特征，并依据短时强降水发生发展的基本条件，基于“配料法”思想，探讨了成都市短时强降水概率预报方法。结果表明：成都市短时强降水事件集中于暖季（4~9月），其中又以7月为最多，并呈明显夜间多发的态势。降水量与降水强度空间分布表现出西多东少特征。筛选出的短时强降水潜势预报因子包括850 hPa比湿、850 hPa假相当位温、K指数、对流有效位能、700 hPa经向风以及700 hPa垂直速度，基本涵盖了短时强降水发生所需的水汽条件、稳定度条件以及抬升条件。基于上述短时强降水潜势预报因子的权重系数，采用二分法建立短时强降水概率预报方程，利用TS评分对2019年夏季的短时强降水日潜势预报效果进行检验，发现概率阈值设定为0.98既能保证漏报次数不会太多，又不至于使预报正确次数明显降低，同时可以保持较高的预报准确率。

Preliminary Study on Probability Forecasting of Flash-Heavy-Rain in Chengdu

Using the hourly precipitation datasets from April to September of 2019, and the hourly datasets ERA-5, the temporal and spatial distribution characteristics of flash-heavy-rain in Chengdu in the past ten years were studied. According to the basic conditions for the occurrence and development of flash-heavy-rain, and the notion of basic ingredients, the probability forecasting of flash-heavy-rain in Chengdu was discussed. The main results are as follows: The flash-heavy-rain events in Chengdu are concentrated in the warm season (from April to September), of which July is the most frequent, and it appears to be more frequent at night. The spatial distribution of precipitation and precipitation intensity is more in the west and less in the east. The selected flash-heavy-rain potential prediction factors including 850mb Specific Humidity, 850mb Equivalent Potential Temperature, K Index, CAPE, 700hPa Meridional Wind and 700hPa Vertical Velocity, which basically covers the water vapor conditions, stability conditions and uplift conditions required for flash-heavy-rain. Based on the weight coefficient of the above flash-heavy-rain potential forecast factors, the probability forecast equation of falsh-heavy-rain was estabilished by dichotomy. The testing result of 2019 shows that when the threshold is set to 0.98, the quantity of omission days and correct days are acceptable, while maintaining a high accuracy rate.