近500a福建汛期旱涝变化特征

Variation Features of Fujian Drought/Flood for the Past 5 Centuries

用FFT、连续和正交小波变换分析了近500a福建汛期旱涝的变化特征.结果表明:1) 福建旱涝等级有2～3a和10a左右的显著周期,但其他显著周期有空间和时间差异;2)近500a福建可以分为3个大的相对干湿期,即干-湿-干阶段,目前处在干旱阶段.从百年变化尺度看,闽北可分为6个干湿阶段,目前已开始向湿润期转换,而闽东和闽南则可分为5个干湿阶段,目前尚处在干旱期.从年代际尺度上看,近百年闽北、闽东和闽南都可以分为4个主要的干湿阶段,闽北目前处在湿润期,闽东和闽南也已进入了湿润期;3)闽北从16世纪末开始到20世纪前期旱涝等级有弱的增加(变干)趋势,而20世纪则有减小(变湿)趋势,闽东20世纪以前有弱的减小(变湿)趋势,20世纪前期明显增大(变干),闽南则无明显趋势.福建3个区域旱涝等级的年际变化的方差贡献皆达到80%以上,而年代际变化的方差贡献占不到15 %,百年尺度变化占5%以下.

The temporal/spatial varition features of Fujian drought/flood for the past 500 years are studied by means of FFT,continuous wavelet (CWT) and orthogonal wavelet transformation (OWT).The analysis show that:1)there are significant 2~3 years and 10 years periodic signals in the drought/flood grade series of Fujian,but there are spatial/temporal variations for other periods;2)on the centurial scale,the past 500 years can be divided into 6 dry/moist phases and currently it is in a dry to moist transition period in the northern region,whereas in the eastern and southern areas the past 500 years can be divided into 5 spells and now it’s still in the dry period,on the decadal scale,the past 500 years can be divided into 4 dry/moist periods and now Fujian is in a moist period;3)in northern regions,the grades series had a weak positive (dring) trend in the period from the end of the 16th century to the beginning of the 20th century and a negative trend in the 20th centry,and in the eastern region the grade series showed a weak decreasing (wetting) trend before the 20th century and an increasing (drying) trend in the first period of the 20th century,whereas the grade series had no obvious trend in the southern region.The variance contribution percentages of interannual,interdecadal and centurial changes to the three subregions’ drought/flood grade variations are >80%,<15% and <5% respectively.