新疆1961—2011年极端降水事件年内非均匀性特征

Inner-annual Inhomogeneity Characteristics of Extreme Precipitation Events in Xinjiang During 1961-2011

利用新疆地区48个气象台站1961—2011年的逐日降水观测资料，根据百分位法定义了不同台站的极端降水阈值，又引入了表征降水时间分配特征的新参数一极端降水事件集中度和集中期，重点分析了新疆的极端降水年内非均匀特征。结果表明：（1）新疆地区极端降水阈值和年平均极端降水量空间分布基本一致，都以天山地区为最大，呈现北高南低的分布。年平均极端降水频次北部高于南部。（2）新疆地区极端降水事件集中度和集中期的空间分布存在一定的差异。总体来说极端降水分布得很密集，各站集中度在0．62～0．9之间，南疆和东疆的集中度大于北疆。新疆地区极端降水主要集中在7月上旬到8月中旬。（3）近51a来，极端降水事件集中度表现为减弱趋势，而集中期表现为增加趋势，表明极端降水越来越分散。（4）极端降水量的季节分配状况和同期的极端降水量存在很好的相关关系。极端降水越分散，集中期越晚，极端降水量越多；极端降水越集中，集中期越早，极端降水量越少。这种相关关系在北疆地区尤为显著。

On the basis of daily precipitation data of 48 stations in Xinjiang during 1961-2011, the extreme precipitation threshold value were defined in different stations according to percentile method and variation characteristics of extreme precipitation events （EPE） in Xinjiang are studied. The inner-annual inhomogeneity characteristics of extreme precipitation events are analyzed by introducing the new parameters that reflect the temporal distribution of precipitation including concentration degree and concentration period. Results shows as follows. 1 ）The spatial distribution of the extreme precipitation threshold value is almost same to the annual average extreme precipitation, which shows that the maximum locates in Tianshan Mountain area, the value in northern Xinjiang is larger than that in the south as same as the extreme precipitation frequency. 2） There are some differences in spatial distribution between concentration degree and concentration period of extreme precipitation events. The range of the extreme precipitation events concentration degree is 0.62-0.9, which shows that the extreme precipitation appears intensively in Xinjiang. The concentration degree of extreme precipitation events in northern Xinjiang is smaller than that in the southern and eastern. The extreme precipitation appears mainly between early July and the middle of August. 3）The concentration degree of extreme precipitation events shows decrease trends in the last 51 years, however, the trends in concentration period Increase, That means that the extreme precipitation appears increasingly dispersively. 4）The concentration degree and concentration period of extreme precipitation events shows a positive correlation with the amounts of extreme precipitation. The amounts of extreme precipitation becomes less with the concentration degree gets higher and the concentration period gets earlier especially in northern Xinjiang, vice versa.