Decadal change in relationship between east Asian and WNP summer monsoons

Abstract

It has been recognized that the intensity of the east Asian (EA) summer monsoon has a negative correlation with that of the western North Pacific (WNP) summer monsoon. Here we show that this relationship is much stronger in the recent decade (1994–2004) than in the epoch before 1994 (1979–1993). The first two leading modes of summer‐mean precipitation over the large region of the WNP and EA region are shown to be associated with two factors: the ENSO development and the WNP summer monsoon fluctuation. The leading mode has changed from an ENSO‐related mode in 1979–1993 to a WNP summer monsoon‐related mode in the recent decade (1994–2004). The summer‐mean mid‐tropospheric geopotential heights that are correlated with the WNP monsoon index also show a marked change in the teleconnection (wave‐train) pattern between 1994–2004 and 1979–1993. All together this evidence suggests that the relationship between the EA and the WNP summer monsoons has experienced a significant decadal change around 1993–1994.