1971—2020年昌吉绿洲主汛期极端降水变化特征

Variation Characteristics of Extreme Precipitation in Main Flood Season of Changji Oasis from 1971 to 2020

选用昌吉回族自治州7个县、市气象观测站1971-2020年主汛期(6-8月)逐日降水量资料,运用线性回归、气候倾向率方法分析各站雨日数、降水量及极端降水的变化规律。结果表明:(1)主汛期雨日数最多的是木垒,年平均为24.26 d;玛纳斯次之,为20.64 d;呼图壁最少,仅19.28 d。雨日数空间分布呈现出明显的北少南多特征,北部低海拔地区少于南部高海拔地区,时间分布上呈单峰型,7月最多。(2)除吉木萨尔雨日数增加外,其他各站雨日数均呈减少趋势;小雨到大暴雨各个量级雨日数占比呈减少趋势;除木垒外,其他各站的小雨对雨量影响最大,在6个降水量级中所占比率超过30%。(3)主汛期微雨及小雨次数贡献率为81.8%,降水量贡献率为33.9%,大雨以上级别的降水次数贡献率仅为7.3%,降水量贡献率却达40.4%,因此将极端降水的标准确定为1 d降水量≥12.1 mm。(4)主汛期极端降水平均强度为20.1 mm,年平均频次为1.5次。降水频次呈增加趋势,20世纪90年代至今处于高发时段。极端降水和暴雨事件主要集中在7月中旬,其次为6月中旬,8月上旬发生次数最少。

Based on the daily precipitation data in the main flood season(June-August)from 1971 to 2020 in 7 meteorological stations in Changji prefecture,the daily precipitation was divided into 6 grades.The linear regression and climate tendency rate methods were used to analyze the variation of rainy days,precipitation and extreme precipitation.The results showed that:(1)The number of rainy days in the main flood season in Changji oasis was the highest at Mulei station,with an annual average of 24.26 d,followed by Manasi,which was 20.64 d.The number of rainy days was the least at Hutubi station,only 19.28 d.The spatial distribution of rainy days showed obvious characteristics of less in the north and more in the south,and less in the low altitude area in the north than that in the high altitude area in the south,and the time distribution was unimodal type,with the largest number in July.(2)Except for the increase in Jimusaer station,the number of rainy days in each station showed a decreasing trend.In terms of the proportion of rain days in each magnitude,from light rain to heavy rain,the proportion decreased with the increase of precipitation level.Except for Mulei,light rain had the greatest impact on rainfall,accounting for more than 30%of the six precipitation levels.(3)The contribution rate of drizzle and light rain in the main flood season of Changji oasis was 81.8%,and the contribution rate of precipitation was 33.9%.However,the contribution rate of precipitation times above heavy rain was only 7.3%,and the contribution rate of precipitation reached 40.4%.Therefore,the standard of extreme precipitation was determined as 1 d precipitation逸12.1 mm.(4)The average intensity of extreme precipitation in the main flood season of Changji oasis was 20.1 mm,and the average annual frequency was 1.5 times.The frequency of precipitation showed an increasing trend,and has been in a high incidence period since the 1990s.Extreme precipitation and rainstorm events were mainly concentrated in mid-July,followed by mid-June,and the least in early August.