Analysis of temporal and spatial distribution characteristics of minutely rainfall in Hubei province

Based on the minutely rainfall data of 2523 surface automatic observation stations from March to September in Hubei province from 2019 to 2022, the spatial and temporal distribution characteristics of 6-min rainfall, as well as the synoptic systems and environment characteristics of the extreme 6-min rainfall were analyzed. The results indicate that: the provincial average of the maximum of 6-min rainfall is 14 mm, and the western average of 6-min rainfall is less than the eastern. The extreme 6-min rainfall in southwest of Hubei is quite large with lower frequency, while the minutely rainfall in eastern of Hubei is large and with higher frequency. From March to May, the frequency of rainfall in Jianghan Plain and southeastern Hubei is high, while in northwestern Hubei which is lower but extreme thus leading a high risk of disaster. From June to July, the frequency of heavy rainfall is obvious higher and more extended. The high frequency center of rainfall larger than 6 mm locates at 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 lager than 3 mm happens more often in Enshi and Yichang located in the transition zone between plain and mountain, and in eastern Huanggang located the south of Dabie Mountains. The frequency of 6-min rainfall shows obvious diurnal variations, and the high period occurs from afternoon to midnight, with the peak from 16:00 BT to 18:00 BT. The high frequency period relates to the afternoon thermal convection and the nocturnal intensifying low-level jet. The synoptic systems of maximum 6-min rainfall in each month divided into 3 types, in which the upper-level trough type occupying more than half, followed by the northwest flow behind trough type and subtropical high type. The extreme minutely precipitation is closely related to the evolution of mesoscale synoptic system.