湖南省资水流域极端降水量时空变异特征及重现期极端降水量的推算

Spatial and Temporal Evolutionary Characteristics of Extreme Precipitation and It’s Estimation for Certain Return Period in Hunan Zishui River Basin

【目的】为了解湖南省资水流域各国家气象站1960-2016年年最大日降水量、年最大过程降水量的时空变异特征。【方法】利用经验正交函数(EOF)分解、空间自相关分析、线性倾向估计法、Mann-Kendall检验、复Morlet小波变换等方法,并基于数理统计方法推算了一定重现期各站点极端降水量值。【结果】①资水流域极端降水量空间上存在"北多南少、西多东少"的特征,地处迎风坡的站点极端降水量值较大,盆地、背风坡处的站点极端降水量较小,极端降水量EOF分解特征向量主要存在3种典型模态,南-北型、西北-东南型和全局型;20世纪80年代后年最大日降水量空间上存在一定的集聚倾向,尤其是2000年后集聚趋势十分显著,表现为明显的两极分化特征,年最大过程降水量则表现出一定的空间负相关性;②流域平均极端降水量呈增加趋势,年最大日降水量气候增长率为2.8 mm/10 a,20世纪80年代后期-20世纪90年代初期是极端降水量突变阶段,空间自相关性和变化趋势均存在显著变化;上游地区极端降水量存在准周期变化规律,准周期为10 a左右;③50 a以上重现期极端降水量分布与极端降水量EOF分解特征向量分布形态高度一致;极端降水量大的站点,其极端降水量随重现期显著增加,极端降水量小的站点,其极端降水量随重现期增加变化不明显。【结论】近年来频发的厄尔尼诺现象与资水流域极端降水量时空变异特征关系密切,其中的具体关联有待进一步研究。

【Objective】The spatial and temporal evolutionary characteristics of extreme precipitation in Zishui river basin were analysed based on the observed daily rainfall data from 1960 to 2016 and the values of extreme precipitation for each national meteorological observatory of certain return periods were also calculated【Method】by using of EOF、spatial auto correlation、Mann-Kendall test、Complex Morlet wave transform and statistical methods.【Result】The results showed that:(1)generally speaking, spatial distribution of the extreme precipitation in Zishui river basin is inhomogeneous which is greater in the west than the east and greater in the north than the south. There are three kinds of typical modes for extreme precipitation, namely the whole region, north-south,northwest-southeast. Annual maximum daily precipitation was characterized of spatial aggregation since 1980 s,the tend of polarization is very obvious after 2000.(2)The value of extreme precipitation has increasing tendency,this is especially true for middle and downstream. There exist a 10 years Quasi-periodic oscillation for extreme precipitation in upstream.(3) When the return period is greater than 50 years, the spatial distribution of extreme precipitation is still inhomogeneous which is larger in the west than the east and larger in the north than the south.The extreme precipitation of certain return period increases with the increasing of return period. The more extreme precipitation, the faster extreme precipitation increases.【Conclusion】The occurrence of El Nino in recently years were thought to be connected with the evolution of extreme precipitation. The relations between El Nino and extreme precipitation of Zishui basin are remain to be discussed.