湖南伏旱期旱涝变化特征及其与前期环流之关联

Relation between Characteristics of Summer Drought and Flood Variation and Antecedent Circulation in Hunan Province

利用1961～2006年7月降水资料和z指数、小波分析及相关分析法，分析了湖南伏早期旱涝多时间尺度变化特征及其与500hPa高度的关系。结果表明：湖南伏早期雨涝指数增大趋势显著，20世纪90年代以来处于雨涝多发期。雨涝指数具有22年、12年、6～7年和3～4年的明显周期；干旱指数具有20年和10年明显周期。旱涝指数与500hPa高度相关分析显示z指数与前期，特别是2月500hPa高度有较好的相关关系，典型涝年东西伯利亚-鄂霍次克海地区500hPa呈明显的负距平，西太平洋副高区为明显的正距平，而典型旱年东西伯利亚-鄂霍次克海地区500hPa呈明显的正距平，西太平洋副高区为明显的负距平。

Droughts and floods from 1961 to 2006 in summer drought seasons in Hunan Province are analyzed by using z index, and the variation characteristics of multi-scale drought and flood activities are analyzed by the wavelet analysis method. The results show that there was a significant increasing trend in the flood index in the past 46 years; floods occurred more frequently from the 1990s. It is also found that there were significant periods of 22 years, 12 years, 6 to 7 years, 3 to 4 years in the flood index, and significant periods of 20 years, 10 years in the drought index. Relation analyses between 500 hPa height and z index show that there existed good correlation between z index and 500 hPa height, especially in February. In heavy flood years, 500 hPa anomalies were prominently negative in the eastern Siberian and positive in the subtropical high pressure zone; in contrast in heavy drought years, 500 hPa anomalies were obviously positive in the eastern Siberian and negative in the subtropical high pressure zone.