1980~2019年夏季青藏高原中东部极端日降水分布特征

基于中国气象局国家基准气象观测站逐日观测资料，采用百分位法对1980~2019年夏季青藏高原中东部地区极端日降水进行定义，分析了不同分位极端日降水的气候分布特征。结果表明:（1）青藏高原中东部夏季降水呈东多西少、中间多南北少的反位相分布特征，且存在显著的年际和年代际变化。（2）99%分位降水阈值普遍在24 mm/d以上，95%分位和90%分位降水阈值维持在12~20 mm/d，75%分位降水阈值则进一步下降至7~9 mm/d。（3）从长期变化趋势看，青藏高原中东部99%分位的极端日降水出现频次呈显著的上升趋势，其余几个分位则以下降趋势为主。（4）相较于99%和90%分位而言，95%分位在青藏高原中东部夏季降水中具有更为突出的贡献，且近40 a来99%分位的贡献在不断增加。（5）青藏高原中东部日降水量介于0.1~10.5 mm，但日降水量的频次波峰和总降水量的波峰位置存在差异，2.4~5.1 mm日降水量在青藏高原中东部降水中具有重要作用。 

Characteristics of Extremely Daily Precipitation Events in the Mid-Eastern Tibetan Plateau during the Summer of 1980~2019

Based on the daily observation data of the National Meteorological Stations of China Meteorological Administration, the extreme daily precipitation events in the middle and eastern Tibetan Plateau during the summer of 1980-2019 were defined by the percentile method, and the climatic distribution characteristics of extreme daily precipitation events in different quantiles were analyzed. The results show that: (1) The summer precipitation in the central and eastern Tibetan Plateau was characterized by an antiphase distribution of more in the east than that in the west, and more in the middle than that in the north and south, and there were obvious interannual and interdecadal variations. (2) 99 % quantile precipitation thresholds were generally above 24 mm / d, 95 % and 90 % quantile precipitation thresholds were maintained at 12~20 mm / d, and 75 % quantile precipitation thresholds were further decreased to 7~9 mm / d. (3) From the perspective of long-term change trend, the frequency of extreme daily precipitation at 99 % quantiles in the central and eastern Tibetan Plateau showed an obvious upward trend, while the other quantiles showed a downward trend. (4) Compared with the 99% and 90% quantiles, the 95% quantile extreme daily precipitation events had a more important contribution to the summer precipitation in the mid-eastern Tibetan Plateau, and the contribution of the 99% quantile was increasing in recent 40 years. (5) The daily precipitation values in mid-eastern Tibetan Plateau ranged from 0.1 mm to 10.5 mm, but the positions of the frequency peaks of daily precipitation and the total precipitation peaks were different. The daily precipitation of 2.4~5.1 mm played an important role in the precipitation in the mid-eastern Tibetan Plateau.