关键词: 阿勒泰地区, 极端降水频数, 极端降水强度

Abstract: In this paper, based on the daily precipitation data of summer(June to August) of seven national basic meteorological stations from 1961 to 2010, NCEP/NCAR data as well, and 74 circulation characteristic data, the thresholds are calculated by the definition of percentile method and the change of summer extreme precipitation is analyzed using a variety of statistical methods including linear trend, variation analysis, Mann-Kendall(M-K), sliding t test, Morlet wavelet transform and correlation analysis methods etc. It is found that:(1) The threshold values of the summer extreme precipitation events in Altay Prefecture were 9~13.1 mm d^-1. The threshold values depended on terrain, and altitude also affected the values. Altitude was also close to the threshold value. They were basically in the exponential relationship, that is to say, the threshold value increased with altitude.(2) In the 50 a, although the annual variation was not obvious, the decadal oscillation of the summer extreme precipitation could be observed. The decadal variations of frequency and intensity were in a good agreement. They were both low in the early 1980s, then increased from the late 1980s until the middle of the 1990s. They got a maximum at the mid-1990s, and then decreased after 2000.(3) In the 50-a, the summer extreme precipitation events had varied smoothly and steady. Hence, a few stations had no mutation records in the past few decades, except for Altay and Fuyun Stations which were the two stations having mutation from the late 1980s to the early 1990s.(4) The atmospheric circulation characteristics such as the North Atlantic North America subtropical high ridge, the North Africa subtropical high ridge and the A-dex of Tibet Plateau are main factors to control the summer extreme precipitation events.

Key words: Altay Prefecture, frequency of extreme precipitation, intensity of extreme precipitation