The time series of drought and flood indices in the Three Gorges ares are constructed according to Z-index system and the multiple time scales variation characteristics of the index series are analyzed by using Morlet wavelet transform method. The atmospheric circulation characteristics in the typical summer drought/flood years are investigated. It is found that the drought/flood variation is characterized by obvious interannual and interdecadal changes in the Three Gorges area. The drought index and the flood index time series have almost anti-phase variations on the annual and seasonal time scales. The Morlet wavelet analyses show that the drought and flood indices in the Three Gorges Reservoir area have remarkable periodic oscillation and obvious local features in different time and frequency distributions. There are quasi-5-year, quasi-9-year, and quasi-15-year interdecadal periodical oscillations.The periodical oscillations of the drought and flood features have significant seasonal differences. In flood years, the atmospheric circulation background in the Three Gorges Reservoir area shows that the anomaly of 500-hPa geopotenrial height field is positive in the Ural Mountains, Siberia, and Lake Balkash, and negative in the Loop area and North China Plain as far as the Sea of Japan The atmospheric circulation anomaly is opposite in drought years.%根据Z指数指标体系,构建了三峡地区旱涝指数时间序列,且利用Morlet小波分析方法研究了指数序列的多时间尺度演变特征和典型夏季旱涝年大气环流特征,结果表明:三峡地区干旱、雨涝有明显不同的年际、年代际特征,年、四季的干旱指数与雨涝指数基本呈反位相特征.三峡地区旱涝指数Morlet小波分析表明,在不同时间和频率域中,有显著的周期振荡,具有较强的局部特征;年旱涝指数主要有准5年、准9年、准15年的周期振荡;旱涝特征周期振荡也具有明显的季节性差异.三峡地区雨涝年的环流背景为乌拉尔山地区、西伯利亚、巴尔喀什湖地区上空位势高度偏高,我国河套地区、华北平原至日本海上空的位势高度偏低;干旱年的环流形式与之相反.
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