Calculation and analysis of the thresholds of hourly extreme precipitation in mainland China

Using two methods in thresholds definition, Generalized Extreme Value (GEV) distribution and percentile measurement, the thresholds of hourly rainfall intensity at 465 stations in mainland China are analyzed on different extreme scales. GEV distribution shows that the thresholds for 2, 5, 10, and 50-year return period share an identical spatial distribution, which exhibits highest values in coastal region of southern China; higher values in the north of the middle and lower reaches of the Yangtze River valley, west of Sichuan basin, and east of northern China; lower values in the midwest of Yunnan, west of northern China, and west of northeast China; lowest values in the western China. Meanwhile, the percentile results have the same distribution pattern as GEV outcomes on a whole, which present higher thresholds in southeast and lower thresholds in northwest. The medians at 465 stations are analyzed. The results indicate that intensity thresholds of the 99.9th percentile are close to intensity thresholds of 2-year return period. Having converted the thresholds of the 99.9th percentile to return period level, it is shown that the return periods are under 2-year in Yangtze River valley and its southern area; longer than 4-year along 35°N; longer than 8-year in parts of northern China and northwest China.