榆中县近42年降水突变及周期变化分析

Abrupt and periodic variation of precipitation in Yuzhong County in recent 42 years

【目的】掌握黄土丘陵区降水特征、趋势变化和周期演变规律.【方法】利用榆中1971-2012年的日降水量资料,采用Mann-Kendall法和小波分析等方法,对榆中42a来的降水变化和突变现象进行了研究.【结果】近42a来区域年降水量变化在231.1～555.5mm,整体呈现减少趋势,气候倾向率为-3.68mm/10a,1971-1979年属于降水最多的年代,榆中年降水量的突变不太明显.四季降水量变化呈现不同的趋势,其中春季和冬季降水量呈现增多的趋势,夏季和秋季降水量呈现减少的趋势.四季降水突变情况有所差异.夏季降水从2009年开始发生了由多到少的突变.秋季降水在20世纪80年代初发生了突变.春季和冬季降水量没有发生突变.区域年降水量存在21a的最强显著周期和28a、8a的尺度变化周期,且8a尺度是榆中最稳定的变化周期.【结论】黄土高原丘陵区降水呈下降变化趋势,具有一定的周期和规律变化.

[Objective] To know the precipitation characteristics, trend change and periodic evolution in the loess hilly region. [Method] The change and abrupt variance of precipitation in Yuzhong was analyzed using the linear regression method, cumulative anomaly method, Mann-Kendall test method and Morlet wavelets analysis method based on daily precipitation data observed at Yuzhong meteorological station from 1971 to 2012. [Result] The annual precipitation varied from 231.1 mm to 555.5 mm, appearing a decrea- sing tendency in recent 42 years, and the climatic trend rate was 3.68 mm/10a, showing that the precipitati- on in 1970s was more than in the other years, and the abrupt change in precipitation is not obvious. The seasonal precipitation showed different trends, the spring and winter precipitation showed increasing trend, and the summer and autumn precipitation appearing decreasing trend. The abrupt variance in precipitation differed among four seasons. Summer precipitation occurred abrupt change since 2009 from high to low. Autumn precipitation abrupt variance happened in the early 1980s. There was no abrupt change in spring and winter precipitation. The annual precipitation fluctuated with significant 21-year period and 28-year and 8-year scale change period. And 8-year scale was the most stable changing period in Yuzhong. [Conclusion] Precipitation show a downward trend in hilly region of loess plateau,with a certain period and the regular variation.