Interdecadal Change in the Effect of Spring Soil Moisture over the Indo-China Peninsula on the Following Summer Precipitation over the Yangtze River Basin

The land surface energy exchange over the Indo-China Peninsula (ICP) is important for regulating regional weather and climate. This work investigates the effect of spring soil moisture (SM) over the ICP on the following summer precipitation over the Yangtze River basin (YRB) during 1961-2010. The results show that the spring SM over the ICP has a significant negative correlation with the following summer YRB precipitation. However, this relationship experiences an obvious interdecadal change with a much stronger correlation in the epoch before the early 1990s (1961-91) than in the later decades (1992-2010). In spring, an abnormally lower SM over the ICP could induce less surface evapotranspiration, increasing local temperature until the summer. Before the 1990s, the resultant anomalous ICP heating raises the local geopotential height, resulting in an excessive westward extension of the western Pacific subtropical high (WPSH). Accordingly, the enhanced southwesterly summer monsoon would transport more moisture to the YRB, intensifying the meiyu front and local precipitation. In the early 1990s, the East Asian summer monsoon underwent an abrupt change with an interdecadal westward extension of the climatic WPSH. Consequently, the similar abnormal ICP surface heating induced by the anomalous SM would have different influences on the monsoonal circulation, causing a much weaker effect on the YRB precipitation in the recent decades.