华北地区极端干旱事件的变化特征

利用华北地区1961—2015年72个测站的月降水资料,采用一元线性回归、M-K非参数检验、小波变换、分形理论等方法,研究了华北地区极端干旱事件的变化特征。结果表明,华北地区极端干旱事件频次呈波动递增趋势,递增率为0.21次/10a。1981—1993年极端干旱事件频次低于平均值;1994—2015年的高于平均值,处于极端干旱期。极端干旱事件频次距平值年代际变化差异较大:1961—1980年极端干旱发生频次距平值正负交替;1981—1993年的为负值;1994—2015年的为正值。华北地区极端干旱事件频次在2003年发生了突变性增加,极端干旱事件频次Hurst指数值为0.55,具有长相关性,未来10年内华北地区极端干旱频次呈递增的发展趋势。

Change Features of Extreme Drought Events in North China

With the precipitation data from 72 stations in the North China region between 1961 and 2015, the change characteristics of extreme drought events are studied by simple linear regression, M K nonparametric test, wavelet transform and fractal theory, etc. The result shows that the frequency of extreme drought events in North China is increasing with fluctuation, and the increase rate is 0.21 times/10a. Extreme drought frequency during 19811993 is lower than the average level, while during 19942015 is higher than average level and in extreme drought period. Decadal variations of anomaly for extreme drought frequency presents large differences, which alternates positive and negative in 19611980, is negative in 19811993 and positive in 19942015. Analysis mutation of the frequency of extreme drought points out that the year 2003 is a mutation. The frequency Hurst exponent of extreme drought events is 0.55 and has long correlation, which points that in North China the development trend of extreme drought frequency will increase in the next decade.