Regional Climate Features And Climate Change Of Hourly Precipitation Over Easern China

Based on 518 stations'hourly precipitation data from 1961 to 2000 over eastern China, firstly the criteria of short-time storm rainfall and severe storm rainfall were discussed. Then diurnal cycles of the extreme precipitation and mechanisms of diurnal cycle in different regions were concluded. Furthermore, trends of hourly extreme precipitation frequencies over eastern China and Western China were analyzed. At last atmosphere conditions were assessed in abnormal years over Western China. Some achievements are highlighted as follows.(1) Studies have shown that hourly extreme precipitation events occurred frequently in the southeastern coastal area, the Mid-lower Reaches of the Yangtze River and Sichuan. The distribution of 20mm/h intense hourly precipitation in China was similar to the rainstorm areas. Therefore, it suggests that to define short range rainstorm with 20 mm/h is appropriate but 50mm/h is too much high for short range heavy storm rain.(2) Hourly heavy precipitation in South China, North China, northeastern part of China and Yunnan focuses on the afternoon-evening, while it focuses on the late night and dawn in the western Sichuan Plateau. Hourly heavy precipitation was obviously in Guizhou, the eastern Sichuan Basin at night.(3) Warm season frequencies of hourly extreme precipitation increased in the most parts of east China, but decreased obviously in North China and its intensity obviously increased in Sichan Basin and Northeastern China. Contrasting to trends of daily extreme precipitation during same periods (1961-2000), hourly extreme precipitation is much better to reflect trends in regional extreme precipitation.Based on 1961-2000 hourly precipitation data in 112 station of Southwest China, frequencies and intensity of hourly precipitation and extreme precipitation in different seasons were further analyzed. The results indicated that:(4) Hourly precipitation frequencies declined in most parts of Southwest China in summer, including the western Sichuan Basin, Yunnan and southern Guizhou, but they increased in the eastern Sichuan Basin and the western Sichuan highland. Hourly extreme heavy precipitation frequencies increased in the western Sichuan Basin, and declined in most parts of Southwest China, including eastern Sichuan Basin, western Sichuan highland, most part of Yunnan and Guizhou. In autumn, trends of hourly precipitation frequencies were negative in most part of Southwest China, however trends of hourly extreme heavy precipitation frequencies were not obvious. Influenced by trends in summer and autumn, when accounting for more than 75 percents of precipitation amount of the whole year, annual total precipitation frequencies increased, but extreme heavy precipitation frequencies declined.(5) In summer, besides the western Sichuan Basin, trends of average rainfall intensity in most parts of Southwest China were positive; meanwhile, trends of extreme heavy precipitation intensity were also positive in most parts of Southwest China. In autumn, average rainfall intensity increased in most parts of Yunnan and Guizhou, and declined in the eastern Sichuan Basin and the western Sichuan highland. Meanwhile, 82 stations for 40 years were used to do the EOF analyses in Western China, it showed that trends of extreme heavy precipitation frequencies over the western Sichuan Basin is quiet different to most parts of the other regions.