基于Climatic Research Unit(简称CRU)的高分辨率月值平均潜在蒸发量和降水资料,构建我国近112年干燥度指数,采用线性倾向估计、Morlet小波分析等方法研究我国东部气候干燥度南北之间的差异及其各自的变化特征。结果表明,近一个多世纪以来,中国东部整体呈现变干趋势,20世纪60年代之后干旱化趋势更加明显。相比南方,北方气候干燥程度对降水的依赖性更强,干旱化速度更大,旱涝随时间的转变更为剧烈;南湿北干的差异进一步扩大,温度的升高对潜在蒸发量的增强作用加剧了干旱化程度。我国东部地区干湿季变化存在差异,干季年际年代际变率明显高于湿季,且干季变化较湿季具有更好的南北空间一致性;南北干湿季的出现时间在近半个世纪也有所变化,干季延后到来,湿季则提前到来的现象,说明干湿季的持续时间均有所延长;此外近半个世纪,北方干湿季均呈现明显的干旱化,南方未表现出类似特征。
英文摘要:
With global warming,droughts have become one of the most serious environmental problems. There are different degrees of drought tendency in some regions of China in recent years. Precipitation and Potential evaporation are selected from the high resolution data of Climatic Research Unit(CRU)to calculate drought index during 1961-2012 in China,and the aridity index is calculated by the ratio of potential evaporation to precipitation to study the aridity difference between north and south China. By separating eastern China into two regions(north and south)and using the linear trend estimation,Morlet wavelet analysis and other methods,variations in droughts and the differences between the dry and wet seasons north and the south of eastern China are analyzed. It shows that:(1)Eastern China is drying during past 112 years,and the trend is more obvious after twentieth Century 60's. The increasing trend of aridity in northern China is faster than that in the south,and the differences between aridity in north and south China expand with time. An increasing aridity is accompanying an increasing temperature,so it can be concluded that the effect of increasing temperature on the potential evaporation intensifies the degree of drought.(2)In addition,sudden turn of drought and flood also increase,which may carry greater challenges for climatic prediction and drying disaster risk. There is a accelerate transformation of 20 years and 2 years in aridity index both over north and south china,and the quasi biennial phenomenon also accelerate after twentieth Century 60 years,but the transition process always is mild in south.(3)There are also differences in the dry and wet season in eastern China. Inter-annual and decadal amplitude of variation in dry season is significantly higher than that in wet season. Compared with the wet season,spatial consistency change is better in dry season. Besides,the time of dry and wet have changed in recent years. The dry season delays while the wet season comes ahead in eastern China,which suggests that both the dry and wet seasons last longer.(4) In addition,in the last half a century,both the dry and wet seasons in north China show a significant trend of drought,but there are not the similar features in south China.