宁夏近50年极端强降水事件的时空变化分析

目的]研究近50年宁夏极端强降水事件的时空变化特征。方法]根据宁夏20个站点1961～2010年的逐日降水资料,采用百分位的方法定义宁夏极端降水事件的阈值,选取极端降水事件的降水量、频率、强度等多个指标,并利用线性回归和M-K非参数统计检验法分析了宁夏极端降水事件的时空分布及变化趋势特征。结果]采用百分位法确定的宁夏近50年平均极端降水阈值大致呈现从南到北逐渐减小的分布状况,阈值较大的区域主要位于宁夏海原以南的固原地区,较小的区域位于宁夏的同心、盐池以北的大部地区,与宁夏气候平均年降水量的分布极为相似;近50年宁夏大部分地区的极端降水频率、极端降水量以减少趋势为主,而极端降水强度呈增大趋势。对麻黄山、六盘山2个典型站的极端降水事件分析发现,麻黄山极端降水频率与极端降水量呈减少趋势,极端降水强度为增大趋势,六盘山极端降水频率、极端降水量与极端降水强度均呈减少趋势;麻黄山年极端降水频率在1994年之前呈减少趋势,1994年以后呈增加趋势,突变发生在2003年;年极端降水强度1984年以来为增加趋势,突变时间为1984年,六盘山从1978年至今为减小趋势。结论]该研究为宁夏气候突变分析提供理论依据。

Analysis on Spatial and Temporal Changes of Extreme Precipitation Events in Ningxia in Recent 50 Years

Objective] The aim was to study the spatial and temporal changes of extreme precipitation events in Ningxia in recent 50 years.Method]Using daily precipitation data at 20 stations in Ningxia from 1961 to 2010,and defining the threshold value of extreme precipitation in each station by percentage method,choosing indicators such as precipitation,frequency and intensity of extreme precipitation events,the characteristics of the spatial and temporal distribution and linear trend of extreme precipitation events in Ningxia were analyzed based on linear regression and M-K non-parameter statistical test method.Result]The percentage method suggested the threshold value of average extreme precipitation in Ningxia in recent 50 years decreased from south to north.The large threshold value was in southern Haiyuan,Tongxin and northern Yancheng,which was similar to the distribution of mean annual precipitation in Ningxia.In recent 50 years,extreme precipitation frequency and extreme precipitation decreased in most part of Ningxia but the intensity tended to strengthen.Study of extreme precipitation in Mahuang Mountain and Liupan Mountain indicated that precipitation frequency,intensity and extreme precipitation reduced.Annual extreme precipitation frequency narrowed and then increased after 1994 and had mutation in 2003.Annual extreme precipitation intensity enhanced since 1984.Mutation took place in 1984.Intensity in Liupan Mountain had weakened since 1978.Conclusion]The study provided theoretical basis for the mutation of climate in Ningxia.