Analysis of temporal and spatial distribution characteristics of flash heavy rain in Hubei Province based on minute rain gauge data

Based on the minute rainfall data of the surface dense automatic stations in Hubei Province from 2010 to 2015, this paper identifies the flash heavy rain events (hereafter FHR) by using the sliding accumulative hourly rainfall, and compares and analyzes the spatial and temporal distribution characteristics of the FHR days, frequencies in six forecast regions, namely, southeastern Hubei, northeastern Hubei, Wuhan, Jianghan Plain, Northwestern Hubei and southwestern Hubei, and then briefly discusses the extreme FHRs. The results show that: (1) The annually averaged FHR days have obvious local characteristics, and the heavy precipitation centers are mainly concentrated in southeastern, northeastern, Wuhan, southwestern and other regions. The monthly change shows a significant single peak feature with the peak in July. (2) The frequency distribution of FHR also has obvious monthly and diurnal variation characteristics. The monthly distributions of peak values are different in different regions with double-peaks (June-July) in Jianghan Plain and southeastern Hubei, the main peak in July and the second peak in June in Wuhan and northeastern Hubei, and the main peak in July and August in Northwest and southwestern Hubei. In addition, the diurnal variations of the FHR frequency have different characteristics with double-peaks in northwestern Hubei (04:00 BT and 19:00 BT), southwestern Hubei (01:00 BT and 17:00 BT), northeastern Hubei (08:00 BT and 16:00 BT), and southeastern Hubei (07:00 BT and 16:00 BT), single-peak in Jianghan Plain (07:00 BT), and multi-peaks in Wuhan (from 07:00 BT to 14:00 BT). (3) The threshold range of extreme FHRs is from 53 mm to 124.8 mm, and its time-varying trait with statistical regularity with high nocturnal occurrence (from 15:00 p.m. to 01:00 a.m.). The spatial distribution is scattered with higher occurrence in Wuhan and lower occurrence in northwestern and southwestern Hubei.