利用安徽省78个气象台站 1961-2009年共49年的逐日气温和降水资料,采用综合气象干旱指数计算每个干旱过程,进而得到各个台站每年的干旱日数.通过趋势分析、EOF分析、功率谱及小波分析、滑动T检验等方法系统分析了近50年安徽省干旱时空特征,结果表明:运用累积频率法对CI指数的阈值进行修正,修正前后值基本一致;安徽省常年干旱日数基本呈纬向空间分布特征,干旱频率自北向南递减;沿淮淮北及江淮之间东部地区干旱日数呈减少趋势,其它地区呈增加趋势,但未通过0.05的显著性检验;干旱日数EOF展开前三个模态累积方差贡献为75%,第一模态全省一致为正,基本呈纬向空间分布;第二模态零线横向将安徽分为南北两部分,北多(少)南少(多);第三模态零线横向将安徽分为三部分,两头多(少)中间少(多);干旱日数主周期为12～13年,次周期为2～3年左右.在12～13年的时间尺度上,近50年干旱日数经历了由少到多3个循环交替.此外,干旱日数在1968年前后存在一次突变.%By using daily precipitation and temperature data from 78 stations of Anhui province during 1961 ～2009, the drought process is calculated by CI index, then the drought days for stations each year are figured out and the spatial-temporal characteristics of drought over Anhui province in recent 50 years is analyzed by trend analysis, EOF, power spectrum analysis, wavelet analysis, moving T-test and so on. The results show that the original and corrected thresholds of CI index which are corrected by the cumulative frequency are basically the same.The distribution of the average drought days during 1971 ～ 2000 is latitudinal and drought frequency descends form north to south. The trend of drought days descends in Huaibei and the east of Jianghuai, and ascends in the other area, but the both have not pass the 0. 05 significance test. The cumulative percent variance of the EOF first three modes reaches 75％, the first mode are plus in all province and the distribution is latitudinal, the zero line transversely makes off north and south pans in the second mode and three parts in the third mode. The main period of drought days is 12 ～ 13 years and the secondary is around 2 ～3 years. In recent 50 years, the drought days experience three circulations on 12 ～ 13 years scale, and the drought days mutate around 1968.
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