Temporal and Spatial Variation Characteristics of Hourly Extreme Precipitation in the Three Gorges Region in 1998 -2020

Abstract

Using the hourly precipitation data from 35 stations in the Three Gorges Reservoir Region （TGRR） from 1998 to 2020， the spatial and temporal variation characteristics of extreme precipitation occurrence were analyzed around the total amount， frequency and intensity of hourly heavy precipitation （≥20 mm·h-1） and hourly extreme heavy precipitation （≥50 mm·h-1） in the TGRR in the past 23 years.The characteristics of hourly extreme precipitation variation in the TGRR before and after 2010 are also compared and analyzed.The results indicate that the frequency and intensity of hourly heavy precipitation and extreme heavy precipitation in the TGRR were abnormally high in 1998.If this year is excluded， the total number of hourly heavy precipitation and extreme heavy precipitation has no significant trend from 1999 to 2020.In recent 23 years， hourly heavy precipitation occurs 3.8 times per station per year on average， and 3.0~5.0 times per year in most stations.The average annual occurrence of hourly extreme heavy precipitation is 5.5 times， and the average annual occurrence is less than 0.25 times in most stations.The average annual occurrence is more in the Jianshi-Xuanen area in the central mountainous area.The spatial distribution of annual mean heavy precipitation and hourly heavy precipitation in the TGRR is quite different.After 2010， the annual mean hourly heavy precipitation decreased by 10.4 mm， mainly in Chongqing area in the west of the TGRR， with an annual mean decrease of 15.5 mm.The annual mean hourly heavy precipitation and its occurrence frequency increased at 31.4% stations， and the increase was more obvious in the Jianshi-Laifeng area in central Hubei Province， and the annual heavy precipitation at five stations increased by 16.1 mm on average.And formed the distribution state with the beginning of construction as the center.The "increase and decrease" of the average number of extreme heavy precipitation for many years before and after 2010 presents an alternating southwest-northeast belt distribution.The average number of extreme precipitation in most regions remained at 0.0~0.5， with little change on the whole.The stations with increasing characteristics of heavy rainfall intensity accounted for 48.6%， and the increasing range of heavy precipitation rain intensity was further expanded.In the Wulong-Changyang area， the rainfall intensity of hourly heavy precipitation increased while the heavy precipitation decreased.On the whole， the increase of heavy precipitation in the TGRR is mainly concentrated in the eastern area closer to the reservoir area， and the influence of hourly extreme precipitation on incoming water in flood season needs to be paid attention to.

Keywords

• three gorges reservoir region
• hourly heavy precipitation
• hourly extreme heavy precipitation
• decadal variation