四川省汛期小时极端降水精细化特征

Refined Characteristics of Hourly Extreme Precipitation in Sichuan Province during Flood Season

使用2012-2021年四川省2985个气象站5-9月逐小时降水资料,分析了小时极端降水的精细化特征.研究结果表明:四川省汛期小时降水在第99百分位出现转折性变化,小时极端降水阈值随海拔升高而减小.总体上小时极端降水贡献率四川盆地最高,攀西地区次之,川西高原最低,其与汛期降水量的多少基本匹配.研究期内各个区域的汛期小时极端降水贡献率均以增加趋势为主,川西高原和攀西地区尤其显著,但空间差异非常大.在一天中,各区域小时极端降水都呈“单峰型”,夜间出现小时极端降水的概率相对更大,不同地区的峰值出现时间有所不同,中午时段均不易出现小时极端降水.研究期内小时极端降水出现峰值更高、谷值更低的变化趋势.小时极端降水过程达峰快、减弱慢,开始时间越晚持续时间越长.四川盆地和攀西地区下午至前半夜多为1~3 h短过程,后半夜多为3~11 h持续过程,而且川西高原的开始时间略晚,持续时间更长.

The refined characteristics of hourly extreme precipitation were analyzed using hourly precipitation data of 2895 meteorological stations in Sichuan Province from May to September from 2012 to 2021.The results show that hourly precipitation in Sichuan Province during the flood season showed a transitional change at the 99th percentile,and the hourly extreme precipitation threshold decreased with the increase of altitude.The contribution rate of hourly extreme precipitation was the highest in the Sichuan Basin,followed by Panxi region,and the lowest in the western Sichuan Plateau,which basically matched with the amount of precipitation during the flood season.In the past 10 years,the contribution rate of hourly extreme precipitation in flood season in each region was mainly increasing,especially significant in the western Sichuan Plateau and Panzhi region,but with very large spatial variations.During the day,the hourly extreme precipitation in all regions showed a“single-peak”pattern,with a relatively greater probability of hourly extreme precipitation occurring at night.The peak time varied from region to region,and hourly extreme precipitation was less likely to occur in the midday.Hourly extreme precipitation has shown a trend of higher peak and lower valley over the last 10 years.The hourly extreme precipitation process peaked quickly and weakened slowly,and the later the start time,the longer the duration.The Sichuan Basin and southwestern Sichuan mountainous areas had a short duration of 1-3 hours from the afternoon to the first half of the night,and a continuous duration of 3-11 hours in the second half of the night.Moreover,the southwestern Sichuan mountainous areas had a slightly later onset and longer duration.