资源环境科技发展态势分析平台

The summer precipitation in South China (SC) has experienced a pronounced interdecadal variation during 1983-2013 with trend transition in the late 1990s. This study quantitatively investigates the precipitation variation and its connection to water vapor transport by combining the Lagrangian trajectory-based Dynamic Recycling Model and the clustering method of self-organizing map. The external moisture outside of SC explains most (84%) of the mean and the interdecadal variation of the summer rainfall, mainly through the southwest transport pathways. A long-distance southwest pathway related to cross-equatorial flow and eastward flow over the Northern Indian Ocean explains 31.5% of mean precipitation and 50.4% of the upward precipitation trend before 1997. The other branch of the southwest pathways has relatively shorter length over North Indian Ocean, South China Sea, and Southeast Asia, explaining 35.7% of the mean and 51.2% of the downward trend after 1997. Also, for the downward trend, the westerly-driven moisture transport over Eurasia acts as the second contributor (32.2%) to the precipitation decrease. However, the western-Pacific pathway explains the smallest portion (<= 3%) of the trends, suggesting weak influence from the subtropical high. The large-scale circulation anomaly in the form of zonal and meridional wave trains control the interdecadal variability of the SC precipitation. It is found that the circumglobal teleconnection and Pacific-Japan teleconnection significantly correlate to the two wave trains, whose match relation strongly modulates the trend transition in the 1990s for the SC summer precipitation.