Search

Abstract: A rainfall index since 1873 was constructed for the middle-lower reaches of Yangtze River basin in the eastern Asia summer monsoon (May–August) based on observations and the 5 grades of dryness/wetness in eastern China. Using data from 4 stations: Shanghai (no missing data), Nanjing, Hangzhou and Wuhan (missing data for years before 1905 and from 1938 to 1945), the sums of rainfall observations for the 4 months May–August at each station for years before 1951 was standardized. Secondly, linear regression analysis using data from Shanghai was used to infer the missing data from the other three stations. Thirdly, regressive results were corrected using the 5 grads of dryness/wetness at each station. Finally, average values were calculated over the 4 stations. For years 1951––2006, standardizations at each of the 4 stations and average over the 4 stations were calculated based on full observations. The homogeneity and change points of mean (the first moment) and of variance (the second moment) in this rainfall index series were detected by applying the scanning t-test and scanning F-test separately. The results show good homogeneity in both of mean and of variance for the two periods 1873–1950 and 1951–2006. Meanwhile, 8 climatic change points in subseries means and in subseries variances were detected on decadal time scales. This index correlates well to the rainfall variation over the middle-lower reaches and south of the Yangtze River basin based on the observational data in 1951–2006. [Copyright &y& Elsevier]