最优TS评分方法在逐时降水订正中的初步应用及评估

PRELIMINARY APPLICATION AND EVALUATION OF OPTIMAL THREAT SCORE METHOD IN HOURLY PRECIPITATION FORECAST

关键词:  最优TS评分订正方法  降水分级订正  逐时降水检验  对比评估

Key words:  optimal threat score method  categorized precipitation correction  hourly precipitation examination  comparative evaluation

摘要:

使用2020年3—9月逐时更新的CMA广东短临3 km数值模式(CMA-GD(R3)模式)1～12 h逐小时降水量资料，利用最优TS评分订正方法(OTS)对逐小时降水量进行分级订正，并分别从整体和分类型降水过程预报订正效果进行了检验和对比评估。结果表明：从整体预报订正性能来看，通过OTS方法对CMA-GD(R3)模式订正后，对于≥1 mm/h及以上量级的降水，OTS均有较好的订正能力，并且随着雨强的增加，其TS评分的改善比率越大；同时，OTS可有效减少各个预报时效的漏报率和空报率，其中漏报率减小更加明显，表现出明显的湿偏差(空报偏多)。从三类暴雨过程逐时降水预报订正效果来看，通过OTS订正之后，对于≥1 mm/h的降水，OTS对三类暴雨类型均有正的订正能力。其中在0.1 mm、1 mm、10 mm、20 mm、35 mm、50 mm 6个量级上，季风型的逐时降水预报表现最好，6个量级的TS评分值分别为0.403、0.232、0.053、0.023、0.009和0.004；在5 mm量级上锋面型的逐时降水预报表现最优，其TS值为0.102。从改善效果来看，经过OTS订正后，在1 mm量级上台风型改善率最大，在5 mm和10 mm量级上锋面型改善率最大，在20 mm、35 mm和50 mm量级上季风型改善率最大。

Abstract:

Based on the hourly precipitation data from the short-term 3 km resolution hourly updated CMA-GD(R3) model simulation, the present study examined the hourly data of precipitation during March-September in 2020, evaluated observational data and data from the CMA-GD(R3) model simulation and compared these data in terms of overall correction and categorized precipitation correction using the optimal threat score (OTS) method. The results are as follows: In terms of overall correction, the CMA-GD(R3) data of precipitation with rain rate ≥ 1 mm/h is well corrected by using the OTS method, and the improvement becomes greater with the increase of rainfall intensity. Using the OTS method, we find the decrease of omission rate is more than that of false alarm rate, and the significant bias is either greater than or equal to 1. As for the correction of hourly precipitation forecast of three types of heavy rainfall (frontal rain, monsoon rain, and typhoon-induced rain), the OTS method can help produce positive correction for precipitation with rain rate ≥ 1 mm/h. The hourly precipitation forecast of monsoon rain is the best on the rain rate categories of 0.1 mm/h, 1 mm/h, 10 mm/h, 20 mm/h, 35 mm/h and 50 mm/h, and their respective threat scores are 0.403, 0.232, 0.053, 0.023, 0.009 and 0.004; on the rain rate category of 5 mm/h, the hourly precipitation forecast of frontal rain is the best, and its threat score is 0.102. Moreover, on the rain rate category of 1 mm/h, the improvement of typhoon-induced rain forecast is the most significant; on the rain rate categories of 5 mm/h and 10 mm/h, the improvement of frontal rain forecast is the largest; on the rain rate categories of 20 mm/h, 35 mm/h, and 50 mm/h, the improvement of monsoon rain forecast is the greatest.