中国暖季短时强降水分布和日变化特征及其与中尺度对流系统日变化关系分析

利用2010—2018年河南省371个气象观测站（包含122个国家站和249个骨干区域站）逐时降水资料，对河南省暖季（5—9月）小时极端降水时空分布特征进行了统计分析。主要结果如下：（1）河南省暖季第99.9百分位小时极端降水阈值、强度、频次和贡献率的局地差异明显，其高值区主要分布在伏牛山南部、黄淮平原东部和淮河流域西南部。（2）河南小时极端降水事件主要发生7、8月，其中7月最多，且有1/4以上为区域性极端降水事件；全省小时极端降水频次日变化表现为明显的双峰型，主峰值出现在傍晚；80 mm·h^-1以上小时极端降水频次日变化呈多峰结构，主峰值出现在夜间。（3）山地、丘陵、城市和平原四类下垫面区域的小时极端降水指标存在差异，城市小时极端降水强度最大，频次最低；山地小时极端降水强度最低，频次最高。（4）四类下垫面小时极端降水日变化虽均表现为双峰型，但也存在明显差异：山地其峰值以夜间为主，傍晚为辅；丘陵其峰值夜间、傍晚并存，且峰值强度接近；平原以及城市则以午后峰值为主，其中城市午后峰值强度更高。

Diurnal variations of warm-season precipitation over Northern China

Based on the hourly precipitation data from 2010 to 2018 at the 371 meteorological stations including the 122 national Automatic Weather Stations (AWSs) and the 249 backbone regional AWSs in Henan, we have conducted a statistical analysis of spatial and temporal distribution characteristics of hourly extreme rainfall in warm season (May to September) in Henan. The main results are as follows. (1) There are obvious differences in the threshold, intensity, frequency and contribution rate of hourly extreme rainfall in the 99.9th percentile in warm season in Henan. Their high value areas are mainly in the south of the Funiu Mountains, the east of the Huanghuai Plain and the southwest of the Hwai River basin. (2) Hourly extreme rainfall events occur mainly between July and August, of which the most is in July, and the regional extreme precipitation event is more than the quater of hourly extreme rainfall events. The diurnal variation of hourly extreme rainfall frequency in Henan is characterized by an obvious bimodal structure, in which the main peak value appears in the evening. The diurnal variation of the frequency of hourly extreme rainfall above 80 mm·h^-1 shows a multi-peak structure, in which the main peak value is at night. (3) There are differences in the hourly extreme precipitation index for the four underlying surfaces including mountains, hill area, urban area and plain. The intensity of hourly extreme precipitation is the highest in the urban area, while its frequency is the lowest. The intensity of hourly extreme precipitation is the lowest in the mountains, while its frequency is the highest. (4) Although the diurnal variation of hourly extreme precipitation under all four types of underlying surfaces shows a bimodal pattern, there are obvious differences in some ways. The peak values of hourly extreme precipitation in the mountains occur mainly at night, followed by evening. Those in hilly area coexist at night and in the evening, and their intensities are comparable. Those in plain and urban occur mainly in the afternoon, and its peak intensity in the afternoon is higher in urban area.