Analysis of temporal and spatial distribution characteristics of minute-scale rainfall intensity in Hubei Province

Based on the minute-scale rainfall intensity data of 2523 surface automatic observation stations from March to September in Hubei Province from 2019 to 2022,the spatial and temporal distributions of 6-min rainfall intensity,as well as the synoptic systems of the extreme 6-min rainfall intensity were analyzed.The results show that:the provincial average of the maximum 6-min rainfall intensity is 14 mm,and the average 6-min rainfall in the west is lower than that in the east.The 6-min rainfall intensity in southwest of Hubei is quite large with lower frequency,while the minute-scale rainfall intensity in eastern Hubei is large and with higher frequency.From March to May,the frequency of rainfall in Jianghan Plain and in southeastern Hubei is high,while in northwestern Hubei it is lower but rainfall is large (more than 12 mm),thus leading to a high risk of disaster.From June to July,the frequency of heavy rainfall is obviously higher and more extensive.The high frequency center of rainfall more than 6 mm is located in northeastern Hubei,which is related to the interaction between the low-level jet during Meiyu and the terrain of Dabie Mountains.From August to September,the rainfall more than 3 mm happens more often in Enshi and Yichang located in the transition zone between plain and mountain,and in eastern Huanggang,located south of the Dabie Mountains.The frequency of 6-min rainfall shows obvious diurnal variations,and the high-frequency period occurs from afternoon to midnight,with the peak from 16:00 BT to 18:00 BT.The high frequency period is related to afternoon thermal convection and the nocturnal intensification of the low-level jet.The synoptic systems of maximum 6-min rainfall in each month are divided into three types,with the upper-level trough type occupying more than half,followed by the northwest flow behind the trough type and subtropical high type.Extreme minute-scale precipitation is closely related to the evolution of mesoscale synoptic system.