【摘要】 以长江中下游地区8个代表性站点1470年～2000年的旱涝等级资料和1951年～2000年5～9月的器测降水量数据为基础,采用EOF、滑动t检验、小波分析等统计技术,对1470年～2000年长江中下游地区干湿演变的时空特征进行了分析.结果表明:(1)旱涝等级资料能够准确表达该区域干湿演变的时空特征;(2)前3个主要模态——全区一致、东西相反、南北相反,基本上反映了该区域干湿变化的主要特征,其中第一模态解释了42.3%的方差;(3)在30年的时间尺度上,区域干湿突变均出现在1850s以前,1550s、1740s,1820s,1837s由干转湿,1620s、1520s和1850s由湿转干,近50a是过去500a中年际气候变率最大的时段;(4)干湿演变的主要周期是117a、40a、30a、18a、5a和2～3a,除了18年和2～3a的周期震荡强弱变化不明显外,其余的周期信号强弱均在18世纪温暖时段前后出现了明显变化.这也意味着,19世纪的寒冷时段并非是17世纪寒冷时段的循环再现,这两个寒冷时段存在着一定的差异.更多还原

【Abstract】 Using the Dryness/wetness grads covering the period of 1470~2000 and instrumental measured precipitation from May to September during 1951 to 2000 from eight stations,with the methods of EOF,moving-ttest and wavelet analysis,we analyzed spatial and temporal characters of the dryness/wetness variations in the lower-middle reaches of the Yangtze River.The results show(1) the dryness/wetness grades could accurately reveal the spatial and temporal characters of dryness/wetness variations in the study area;(2) the first three modes which are featured by accordant all over the region,contrary in west-east and in north-south,indicate the main spatial patterns of the dryness/wetness variation,and the first mode accounts for 42.3% of whole variance;(3) at the 30-year scale,the abrupt changes of dryness/wetness occurred before 1850s,conversions from dry condition to wet condition occurred in 1550s,1740s,1820s and 1837s and conversions from wet condition to dry condition occurred in 1620s,1520s and 1850s;the greatest variability occurred in the past 50 years;(4) the dryness/wetness variations had the significant cycles of 117-year,40-year,30-year,18-year,5-year and 2~3-year;excluding the cycles of 18-year and 2~3-year,other’s amplitude changed evidently through the 18th century.It may be implicated that the 19th century was not the copy of the 17th,though both of centuries were featured by cold condition.更多还原