Abstract:

In order to find a proper reanalysis dataset which can best capture the precipitation characteristics of China,the multiyear and yearly annual,seasonal and monthly mean anomaly correlation coefficients and the root mean square errors of four reanalysis precipitation datasets (PREC/L,CMAP,GPCP and NCEP2) and the raingauge records were compared from January 1979 to December 2003 based on the area of the middlelower reaches of the Yangtze River (26°N~34°N，105°E~122°E).All the four reanalysis datasets and observation are monthly data.The data of observation,CMAP,GPCP and NCEP2 were interpolated to the same resolution as PREC/L with resolution 05×05 (longitude×latitude) and the comparison of the precipitation characteristics of annual,seasonal and monthly variations was based on the interpolated data.Results indicated that all of the four reanalysis datasets can capture the spatialtemporal characteristics of precipitation over this region quite well,in which the PREC/L data were the best datasets to consist with the observational data.The anomaly correlation coefficients (the root mean square errors) between four reanalysis precipitation datasets and the raingauge records were descending (increasing) gradually from PREC/L,CMAP,GPCP to NCEP2.Finally,the spatial and temporal characteristics of precipitation in the middlelower reaches of the Yangtze River were analyzed by the methods of correlation,Empirical Orthogonal Function (EOF) and spectrum analysis using PREC/L and observational data.The correlation coefficients of precipitation,the modes and principal components of first two EOF eigenvectors between PREC/L and the observational were above 096.Spatial pattern of the first two EOF modes exposed that the summer precipitation in the southeastern China was out of phase with that in the northwestern China,and that in the southern China was out of phase with that in the northern China.Spectrum analysis indicated two significant periods with 23 and 31 years existed in the variation of the summer precipitation.The temporal variations of the first two EOF eigenvectors of the summer precipitation had the significant periods of 23 and 28 years,all of these significant periods are above 95% confidence level of red noise test.

Key words: PREC/L, GPCP, CMAP, NCEP2, the middlelower reaches of the Yangtze River, precipitation