1961—2017年青藏高原极端降水特征分析

基于青藏高原78个气象站点的逐日降水数据,采用百分位阈值法确定极端降水阈值,计算极端降水指数并分析其时空分布特征,以期为区域气候变化预测及防灾减灾对策的制定提供参考。结果表明：（1）1961—2017年青藏高原年降水量表现出上升趋势,上升速率为8.06 mm/10 a,多年平均降水量达472.36 mm。78个站点的年降水量倾向率最小值为-25.46 mm/10 a,最大值为43.02 mm/10 a,有15.38%的站点降水在下降,较为集中地分布在高原的东部和南部,其余84.62%的站点降水量在上升。（2）青藏高原各站点极端降水阈值的平均值为23.11 mm,取值范围为7.84~51.90 mm。高值中心出现在横断山区的贡山和木里,低值中心出现在柴达木盆地及昆仑山北翼区。（3）青藏高原各站点的极端降水量、极端降水日数和极端降水贡献率均表现出了明显的上升趋势,极端降水强度虽然也在上升但趋势并不明显,表明青藏高原极端降水量的上升并非是极端降水的强度引起的,而是由极端降水频次的上升引起的。柴达木盆地的极端降水量和极端降水日数虽然并没有表现出高值水平,但该地区的极端降水贡献率却表现出较高水平,表明该区域虽然降水量较少,但是降水往往以极端降水的形式产生。

Characteristics of extreme precipitation over the Qinghai-Tibet Plateau from 1961 to 2017

Using the daily precipitation data of the long-term series of meteorological stations on the Qinghai-Tibet Plateau, the percentile threshold method is used to determine the extreme precipitation threshold, calculate the extreme precipitation index and analyze its spatial and temporal distribution characteristics, in order to provide reference for regional climate change prediction and disaster prevention and mitigation countermeasures. The results show that: (1) From 1961 to 2017, the annual precipitation of Qinghai-Tibet Plateau showed an upward trend, with a rate of 8.06 mm/10 a, and the average annual precipitation reached 472.36 mm. The minimum precipitation tendency rate of 78 stations is -25.46 mm/10 a, and the maximum value is 43.02 mm/10 a. The precipitation of 15.38% of the stations is decreasing, which is mainly distributed in the east and south of the plateau, and the precipitation of the remaining 84.62% of the stations is increasing. (2) The average threshold value of extreme precipitation in the Qinghai-Tibet Plateau is 23.11 mm, with error values ranging from 7.84 mm to 51.90 mm. The high value centers are located in Gongshan and Muli of Hengduan Mountains, while the low value centers are located in the northern flank of Qaidam Basin and Kunlun Mountains. (3) The extreme precipitation, the number of days of extreme precipitation and the contribution rate of extreme precipitation at all the stations in the Qinghai-Tibet Plateau show an obvious upward trend. Although the intensity of extreme precipitation is also rising, the trend is not obvious, which shows that the increase of extreme precipitation in the plateau is not caused by the intensity of extreme precipitation, but by the increase of the frequency of extreme precipitation. Although the extreme precipitation and days of extreme precipitation in the Qaidam Basin do not show a high value level, the contribution rate of extreme precipitation is larger, which suggests that although there is less precipitation, extreme precipitation events frequently occur in this area.