关键词: 旱涝分布, 旱涝史料, 特征向量, 旱涝型, 经验正交函数分析, 总方差, 旱涝等级, 夏季降水, 超长期预报, 雨带

Abstract: This article is a study of droughts and floods in China by using chronological materials. The spatical characteristics of distributions of droughts and floods were exa-mined by empirical orthogonal function analysis for 25 stations in last 500 years, for 100 stations in last 100 years using historical documents, and for 100 stations in last 24 years using instrumental rainfall data. The first three eigenvectors combine to yield a picture of zonal distribution of droughts and floods. But the high-order eigenvectors give a rather meridional character. Comparison of eigenvectors for historical docu-ments and for instrumental data shows a good accordance. It indicates that the histori-cal documents of droughts and floods may be satisfactorily used to investigate variations of summer rainfall during historical time.Furthermore, the full set of historical documents for 500 years has been divided into five groups to search into the stability of eigenvectors. Bach group consists of 100 years, that is 1471-1570, 1571-1670 and so on. Eigenvector charts for each group show a very similar characteristics. It indicates that the spatical characters of the drought and flood distribution remain principally unchanged at least in recent 500 years.The distribution of droughts and floods in China has classified into six types:1a, floods all over country, mainly in Chang Jiang,It, floods in Chang Jiang, droughts in the North and the South,2, floods in the South, droughts in the North,3, droughts in Chang Jiang, floods in the North and the South,4, floods in the North, droughts in the South,5, droughts over all country.The chronicles of types of droughts and floods in last 500 years are given. The method of classification is reviewed and the change of frequency of types in last 500 years is discussed.