Interdecadal change of the controlling mechanisms for East Asian early summer rainfall variation around the mid-1990s
East Asian (EA) summer monsoon shows considerable differences in the mean state and principal modes of interannual variation between early summer (May–June, MJ) and late summer (July–August, JA). The present study focuses on the early summer (MJ) precipitation variability. We find that the interannual variation of the MJ precipitation and the processes controlling the variation have been changed abruptly around the mid-1990s. The rainfall anomaly represented by the leading empirical orthogonal function has changed from a dipole-like pattern in pre-95 epoch (1979–1994) to a tripole-like pattern in post-95 epoch (1995–2010); the prevailing period of the corresponding principal component has also changed from 3–5 to 2–3 years. These changes are concurrent with the changes of the corresponding El Nino-Southern Oscillation (ENSO) evolutions. During the pre-95 epoch, the MJ EA rainfall anomaly is coupled to a slow decay of canonical ENSO events signified by an eastern Pacific warming, which induces a dipole rainfall feature over EA. On the other hand, during the post-95 epoch the anomalous MJ EA rainfall is significantly linked to a rapid decay of a central Pacific warming and a distinct tripolar sea surface temperature (SST) in North Atlantic. The central Pacific warming-induced Philippine Sea anticyclone induces an increased rainfall in southern China and decreased rainfall in central eastern China. The North Atlantic Oscillation-related tripolar North Atlantic SST anomaly induces a wave train that is responsible for the increase northern EA rainfall. Those two impacts form the tripole-like rainfall pattern over EA. Understanding such changes is important for improving seasonal to decadal predictions and long-term climate change in EA.
KeywordsEast Asian summer monsoon El Nino-Southern Oscillation (ENSO) North Atlantic Oscillation (NAO) Philippine Sea anticyclone Prediction
This work was supported by the National Research Foundation (NRF) foundation of Korea (NRF) through a Global Research Laboratory (GRL) grant of the Korean Ministry of Education, Science and Technology (MEST, #2011-0021927) and International Pacific Research Center (IPRC), which is in part supported by Japan Agency for Marine-Earth Science and Technology (JAMSTEC), National Oceanic and Atmospheric Administration (NOAA), and National Aeronautics and Space Administration (NASA). This is the School of Ocean and Earth Science and Technology (SOEST) publication number 8913 and IPRC publication number 973. MinHo Kown was funded by the Korea Meteorological Administration Research and Development Program under grant CATER 2012-3071. The comments and suggestions of two anonymous reviewers are greatly appreciated.
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