The regional variabilities of the summer rainfall in China and its relation with anomalous moisture transport during the recent 50 years

The inter-decadal variability of the summer rainfall and its possible partitions in China have been investigated by using the observational rainfall data of 448 stations in China and the monthly NCEP/NCAR reanalysis dataset for 1951-2006. The possible mechanisms of the summer rainfall in every region of China are also discussed from the angle of the ariability of monsoonal moisture transport. Our main results are as follows: (1) there are three abrupt changing periods in the summer rainfall of China since 1951, i.e: 1956-1960, round 1980 and after 1993, whose significant abrupt characteristic in the area east of 90°E is that the rainy regions has been moving southward, while in the one west of 90°E moving northward around the jump points; (2) as to the summer rainfall during the recent 56 years over the eastern China east of 110°E, the rainy regions have moved southward to the middle and lower reaches of the Yangtze River from North China after 1980, and moved southward further to South China since 1993; (3) the analyses of the correlation coefficients of the summer rainfall over the regions of the eastern China with 850 hPa wind field and the integrated moisture transport, respectively, show that in the eastern China east of 110°E, there exist anomalous southeastward monsoonal water vapor transport south of the precipitation regions, while anomalous northward monsoonal water vapor transport north of them, whose convergence leads to the summer rainfall. Consequently, the anomalous moisture transport of the southeast monsoon directly from the south of subtropical high and the anomalous moisture transport of northerly winds from the north cold troughs are the important factors of the summer precipitation over the eastern China; generally, it was however believed that the anomalous rainfall over the eastern China resulted from the anomalous monsoonal moisture transport originated from the Bay of Bengal (BOB), which may require further studies. In a word, as to the flood in the eastern China, attention should be paid to the anomalous southwestward monsoonal moisture transport directly or via the South China Sea indirectly from west of the Northwest Pacific subtropical high.