Temporal and spatial distribution characteristics of short-time heavy rainfall in Guizhou Province

Based on the hourly precipitation data at 84 national meteorological stations in Guizhou Province from 2005 to 2018, the spatial and temporal distribution characteristics of 1-hour short-time heavy precipitation and 3-hour precipitation in Guizhou Province are analyzed by using the statistical diagnostic analysis method combined with considering the topographic characteristics and distinguishing the precipitation magnitude. The results show that: (1) There are 5981 short-time heavy rainfall events in 14 years, with an average of 427.2 events per year. Its spatial distribution is closely related to the terrain characteristics, which is more evident in the south than in the north, more evident in the east than in the west. The"bell mouth"terrain in southwestern Guizhou and the overlap area of the"bell mouth"terrain on the south side of Leigong Mountain in the southeast and the valley terrain are areas with high incidence of short-time heavy rainfall. According to the classification statistics of short-time heavy rainfall, 99% of the short-time heavy rainfall was concentrated in the first two grades with lower rainfall intensity, while the short-time heavy rainfall with R_1H ≥ 80 mm occurred only 5 times in the 14 years. The spatial distribution trend of the maximum rainfall intensity at each station is consistent with that of the total number of short-time heavy rainfall events, which is generally greater in the south than in the north, and greater in the middle and east than in the west. The average rainfall intensity is strong in the south and weak in the north. (2) The annual variation curve shows that during the period of 2005-2013, the number of short-time heavy precipitation events is mostly below the average annual value (427.2), reaching the lowest value of 275 in 2011. The number of short-time heavy precipitation events suddenly increased to 564 in 2014, continued to increase to the maximum value of 662 in 2015, and then quickly fell back to a slightly higher value than the annual average. The interannual variation of short-time heavy rainfall at each station has a large dispersion in the high incidence area and a small dispersion in the low incidence area of northwest Guizhou. The monthly variation curve is single peak type, with high incidence period from May to August and peak value in June. The short-time heavy rainfall is mainly local precipitation at a single station, and there are a few cases with more than three stations occurring at the same time mostly in June. The first ten days of short-time heavy precipitation appear early in the east, late in the west, early in the south, and late in the north. The last ten days are early in the west and late in the east, and early in the north and late in the south. The largest occurrence probability of short-time heavy rainfall in each station is concentrated in the 16th to 18th ten days (i.e. June). The diurnal variation of short-time heavy precipitation showed a single peak type, with a high incidence from 21:00 to 07:00 the next day, and low incidence around 12:00 pm. The spatial distribution characteristics of the diurnal variation of short-term heavy precipitation are mainly concentrated in the western part of Guizhou in the evening to the first half of the night, and mostly in the eastern and southern regions of the later half of the night, and less frequently in the whole province around noon. (3) The spatial and temporal distribution of 3-hourly precipitation is similar to that in R_1H, but there are some differences in some parts.