Interdecadal variability of the relationship between the East Asian winter monsoon and ENSO

The authors examine relationships between the East Asian winter monsoon and the ENSO, particularly on the interdecadal timescales. Based on the analyses of SLP data from 1899 to 1997, the East-Asian winter monsoon index (WMI) is defined as the zonal difference of SLP between similar to 120 degrees E and similar to 160 degrees E. It is found that 18 out of 28 strong winter monsoon years are either before the development of an El Nino or during the decaying La Nina event, 12 out of 28 weak winter monsoon are before the development of a La Nina or during the decaying El Nino event. There is a significant positive correlation coefficient value of about 0.49 between the normalized 11-yr running mean of WMI and ENSO index, however, the WMI-ENSO relationship is not consistently highly correlated. The temporal evolution of correlation between WMI and ENSO indices in both 11-yr and 21-yr moving window shows that the WMI-ENSO relationship clearly undergo low-frequency oscillation. Obviously, both observational and IPSL air-sea coupled modeling WMI index has a near-decadal peak with PDO timescales and internal peaks with ENSO timescales by applying the Multitaper method. Moreover, the cross wavelet and wavelet coherence analysis of WMI/ENSO indicate that there is a larger significant sections with an in phase behavior between WMI and ENSO at period of 20-30 yrs, suggesting that the interdecadal variation of the WMI-ENSO relationship might exist.