基于SPEI指数的华南春季旱涝时空特征

基于1961—2016年逐年华南春季SPEI指数,采用滑动t检验、Morlet小波分析、EOF分解等方法,讨论华南春季旱涝时空变化特征。结果表明:(1)华南春季在20世纪60年代处于干旱期,70年代至90年代初处于雨涝期,90年代初至21世纪初出现大幅度旱涝转换,以后又进入干旱期。华南春季1983年以前呈现趋湿润化;在1983年经历了由上升到下降的显著突变,后呈现趋干旱化;在2011年经历了由下降到上升的显著突变,后呈现趋湿润化。(2)在周期特征上,华南春季旱涝在20世纪70年代中期存在3年左右的显著周期变化,在20世纪60年代前中期和90年代存在4~6年的显著周期变化。(3)华南春季SPEI指数的多年变化趋势并不显著,仅韶关具有显著洪涝化趋势、南宁具有显著干旱化趋势。(4)SPEI指数EOF分解第1模态揭示华南春季旱涝在空间上为全区一致型,第2模态为东西反位相变化型。

Spatiotemporal Characteristics of Springtime Drought and Flood in Southern China Based on the SPE Index

Based on annual standardized precipitation evapotranspiration(SPE)index from 1961 to 2016 and with the methods of t-test,Morlet wavelet analysis and EOF decomposition,this work discusses the characteristics of spatiotemporal variation of springtime drought and flood in southern China.The result is shown as follows.(1)For the springs in southern China,the 1960 s was in a drought period,the 1970 s through the early 1990 s was in a flood period,and the early 1990 s through the early 21 th century experienced a substantial shift from flood to drought before shifting to a drought period again.Prior to 1983,it tended to be wetter in this part of China.A significant abrupt change was observed in 1983 in which the index ascended before descending,showing a trend of drying up.Another significant abrupt change occurred in 2011 in which the index descended before ascending,becoming wetter again later.(2)For the characteristics of periodicity,the drought and flood in southern China experienced significant periodic variations at around 3 years in the mid-1970 s and at 4 to 6 years in the early and middle 1960 s and the 1990 s.(3)Except for Shaoguan where the SPE index shows a significant wetting trend and Nanning where it has a significant drying-up trend,it is not significant on the scale of multiple years across southern China.(4)The first mode of EOF decomposition of the SPE index reveals that the springtime drought and flood in southern China is spatially consistent across the whole region while the second mode varies anti-phased on the east-west direction.