1428 / 2019-08-10 14:28:45

Changes of El Niño-Asian summer monsoon relationship during last half millennium

9、大气科学与全球变化 > 专题3：亚洲季风变异特征和机理

The Asian summer monsoon (ASM) is highly correlated to different phase of El Niño, with break of Indian summer monsoon (ISM) during developing phase and flood over eastern China caused by western North Pacific (WNP) anomalous anticyclone during decaying phase. This relationship, however, is not stable over the past few centuries. In reconstructions of the last half millennium, relationship between El Niño and ASM undergone significant interdecadal change, manifested in two leading modes, i.e., the uniform mode (UM) and dipole mode (DM) between the ISM and the Philippines, for both El Niño developing and decaying summers. The UM, explaining largest variance of the post-El Niño WNP anomalous anticyclone, is highly correlated to the effective solar radiation (ESR) change. The weakened ESR during 1640s may be one reason for the collapse of Ming dynasty, causing an WNP anomalous cyclone in the post-El Niño and a mega drought over eastern China. The DM, related to the drought over ISM, is highly correlated with the Atlantic Multi-decadal Oscillation since 1850. The CESM-last millennium ensemble (LME) reproduces these two leading modes very well. The simulated UM is found to be highly related to the Interdecadal Pacific oscillation (IPO), which means that the weakened ESR is related to a La Niña-like IPO during the Little Ice Age from 1640 to 1850. The ensemble mean of the CESM-LME, however, cannot reproduce the actual phase of IPO, challenging correct simulation of climate response to external forcing in our current state-of-the-art models.