新疆阿勒泰地区近50 a夏季极端降水事件变化特征

利用新疆阿勒泰地区近50 a(1961-2010年)7站夏季(6-8月)逐日降水资料、NCEP/NCAR资料及大气环流指数,采用百分位定义法确定各站夏季极端降水事件阈值,运用线性趋势、突变分析、滑动t检验、Morlet小波分析及相关分析等方法来分析该地区夏季极端降水事件的气候变化.研究表明:阿勒泰地区各站夏季极端降水事件阈值为9.0~13.1 mm·d^-1,阈值存在明显的空间分布差异,且地形及海拔高度对该地区夏季极端降水事件阈值均有影响,海拔高度与阈值两者基本呈指数关系.近50 a来阿勒泰地区夏季极端降水频数及强度的年代际变化具有较好的同步性,均表现为20世纪80年代中期之前频数(强度)偏少(弱),80年代中期以后频数(强度)增多(增强),并于20世纪90年代中期达到最多(最强),但进入2000年后频数(强度)开始减少(减弱).近50 a来阿勒泰地区夏季极端降水事件年际变化的持续性较好,大部分站均没有出现显著性突变,只有阿勒泰、富蕴站在20世纪80年代末期及90年代初出现了明显的突变.北非大西洋北美副高脊线、北非副高脊线、西藏高原A指数是影响该地区夏季极端降水事件的主要因子.

Variations of summer extreme precipitation events in Altay Prefecture,Xinjiang Region,from 1961 to 2010

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.