Abstract
The secular change of the Asian monsoon (AM)-El Niño–Southern Oscillation (ENSO) relationship has been recognized as a specter for seasonal forecast. The causes of such changes have not been well understood. How the monsoon-ENSO relationship underwent secular changes beyond instrumental period has rarely been discussed. Here we explore the multidecadal to centennial changes of the AM-ENSO relationship with the recently compiled Reconstructed Asian summer Precipitation (RAP) dataset (1470–2013) and multiple ENSO proxy indices. During the past five centuries, two leading modes of interannual variability of RAP are found to be associated with the ENSO developing and decaying phases, respectively. The mechanisms behind the modern monsoon-ENSO relationship can reasonably well explain the past monsoon behavior. In response to a developing ENSO, precipitation anomalies from the Maritime Continent (MC) via India to northern China are in phase, and this “chain reaction” tends to be largely steady since around 1620 AD when the Indian summer monsoon abruptly strengthened. Further, the strengthening of the link between developing-ENSO and Indian-northern China rainfall since 1620 AD concurred with a phase reversal of the Pacific Decadal Oscillation. During the decaying phase, however, the summer rainfall-ENSO relationship over the Yangtze River Valley-southern East China (YRV-SEC), the MC and central Asia, has gone through large multidecadal to centennial changes over the past five centuries. A remarkable reversal of sign in the AM-decaying ENSO relationship occurred roughly from 1740 to 1760 over the YRV-SEC and MC, which may be associated with the long-term strengthening of ENSO intensity. Future research should continue focusing on revealing the possible causes of the low-frequency changes in the monsoon-ENSO relationship using general circulation models and paleoclimate proxy reconstructions.
Highlights
The Asian monsoon (AM) system has been extensively studied owing to its great significance and dynamic complexity (Wang 2006)
The Reconstructed Asian summer Precipitation (RAP) is proved to have recorded the phase-dependent influences of the El Niño–Southern Oscillation (ENSO) on Asian summer precipitation since 1470
The second mode shows variation centers over the Yangtze River Valley (YRV), which is associated with the decaying phase of ENSO and/or the rapid transition of the biennial component of ENSO
Summary
The Asian monsoon (AM) system has been extensively studied owing to its great significance and dynamic complexity (Wang 2006). During the decaying phase of an El Niño event, the subtropical EASM and the Meiyu/Baiu frontal rainfall tend to enhance (e.g., Fu and Teng 1988; Huang and Wu 1989; Zhang et al 1996; Lau and Sheu 1988; Chang et al 2001) through the variation of the western North Pacific (WNP) subtropical high and its interaction. If one does not distinguish between the developing and decaying phase of El Niño (La Niña), the simultaneous correlation between summer rainfall in East Asia and the SST anomalies in the eastern equatorial Pacific would not be significant during instrumental period (Chen et al 1992)
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