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
120 E and 160 E. It is found that 18 out of 28 strong
winter monsoon years are either before the development
of an El Ni~no or during the decaying La Ni~na event, 12
out of 28 weak winter monsoon are before the development
of a La Ni~na or during the decaying El Ni~no 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 lowfrequency
oscillation. Obviously, both observational and
IPSL air-sea coupled modeling WMI index has a neardecadal
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 signifi-
cant 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.