Asian-Pacific Oscillation index and variation of East Asian summer monsoon over the past millennium

To study the long-term variation of the East Asian summer monsoon(EASM),the Asian-Pacific Oscillation index(IAPO),representing a zonal thermal contrast between Asia and the North Pacific,is recon-structed over the past millennium.During the Little Ice Age(LIA),the variability of the reconstructed IAPO is closely linked to dry-wet anomalies in eastern China on the centennial scale.This correlation pattern is consistent with the observation during the current period,which suggests that the reconstructed IAPO may generally represent the centennialscale variation of the EASM and rainfall anomalies over eastern China during the LIA.