The Recent Interdecadal and Interannual Variation of Water Vapor Transport over Eastern China

The climatological characteristics and interdecadal variability of the water vapor transport and budget over the Yellow River-Huaihe River valleys (YH1) and the Yangtze River-Huaihe River valleys (YH2) of East China were investigated in this study, using the NCEP/NCAR monthly mean reanalysis datasets from 1979 to 2009. Changes in the water vapor transport pattern occurred during the late 1990s over YH1 (YH2) that corresponded with the recent interdecadal changes in the eastern China summer precipitation pattern. The net moisture influx in the YH1 increased and the net moisture influx in the YH2 decreased during 2000--2009 in comparison to 1979--1999. Detailed features in the moisture flux and transport changes across the four boundaries were explored. The altered water vapor transport over the two domains can be principally attributed to the additive effects of the changes in the confluent southwesterly moisture flow by the Indian summer monsoon and East Asian summer monsoon (related with the eastward recession of the western Pacific subtropical high). The altered water vapor transport over YH1 was also partly caused by the weakened midlatitude westerlies.