体现大尺度特征的区域持续性强降水过程定义指标

利用1961—2017年共57年中国地面观测站日降水资料，采用滑动平均、百分位和点面相关分析等方法，根据延伸期预报特点以及监测预报和研究需求，着眼于体现强降水过程的区域性、持续性和致灾性，并兼顾区域气候特征和普适性，建立区域持续性强降水过程定义指标。根据该指标查找判断我国东部四个关键区域（华南、长江、黄淮、华北）的历史降水过程，1961—2017年期间共有557次区域持续性强降水过程，平均每年约10次，其中华南、长江、黄淮、华北分别有267、155、78、49次，平均每年各有4.7次、2.7次、1.4次和0.9次，呈由南向北递减的分布。统计评估结果表明，该指标能客观地判断出持续影响同一区域的相对稳定类型的大尺度持续性强降水过程，适用于延伸期业务服务和研究。 

A DEFINITION INDEX REFLECTING LARGE-SCALE CHARACTERISTICS OF REGIONAL PERSISTENT HEAVY RAINFALL EVENTS

According to the characteristics of extended forecast and research, a definition index for regional persistent heavy rainfall events is designed with the 57-year (1961—2017) data of daily precipitation observations in China, using the methods of sliding average, percentile and point-to-field correlation analysis. This index focuses on the process which is regional, persistent and disaster-causing, and considers the regional climate characteristics and universality. According to this index, the historical processes over four key regions in eastern China (south China, Yangtze River, Huang-Huai and north China) are identified. There are 557 regional persistent heavy rainfall events in total during 1961—2017 over these four key regions, with an average of about 10 events per year. Among them, there are 267, 155, 78, and 49 events in south China, the Yangtze River region, the Huang-Huai region and north China, with an average of 4.7 events, 2.7 events, 1.4 events and 0.9 event per year respectively, showing a decreasing distribution from south to north. The statistical and evaluation results show that the index can objectively identify the large-scale persistent heavy rainfall events that continuously affects the same region, and thus the index can be applied to operation and research.