关键词: 极端降水事件, 时空变化, 怒江流域, 西藏

Abstract: Based on the daily precipitation datasets recorded by 9 meteorological stations in the Nujiang River Basin in Tibet during the period from 1971 to 2010, the thresholds of extreme precipitation at these stations were defined using 99 percentile values, and the spatiotemporal change of extreme precipitation events in the basin was analyzed. The results show that the thresholds of extreme precipitation varied in a range of 20.6-33.8 mm in the Nujiang River Basin, and the spatial distribution of extreme precipitation thresholds was consistent with annual precipitation. In recent 30 years (1981-2010), the maximum daily precipitation was in an increase trend in most areas including Nagqu, Baxoi and Zayu, especially in Zayu where the increase rate was 5.2 mm•(10a)^-1. The frequency of extreme precipitation tended to an increase in Dengqen, Baxoi and Zayu, but it decreased at other stations with rates of -0.06--0.41 d•(10a)^-1. The annual extreme precipitation increased significantly with a rate of 29.4 mm•(10a)^-1 at Zayua, changed slightly at Zogang, and was in a decrease trend with rates of -1.0--27.2 mm•(10a)^-1 at other stations. In addition, the extreme precipitation intensity increased with rates of 0.6-6.2 mm•d^-1•(10a)^-1 at Nagqu, Sog, Zogang and Zayu, it was in a decrease trend at Amdo and Dengqen, but there was no change at Biru, Lhorong and Baxoi. It was also found that there was a significant 4-5year period of frequency of extreme precipitation, maximum daily precipitation, extreme precipitation and extreme precipitation intensity before the 1990s, and a significant 2-4year period after 2000.

Key words: extreme precipitation event, spatiotemporal change, Nujiang River Basin, Tibet