For the recent years we have added the Optimum Interpolation
SST (OISST) data set (Reynolds and Smith 1994).
We also use the monthly precipitation analysis created by
Xie and Arkin (1996) covering the period January 1979 to
December 1998. Table I lists 'strong' and 'weak' monsoon
years selected following the criterion described above and E1
Nifio and La Nifia years based on Nino3 (150W-90W,5S-5N)
SST anomalies together with a list of 'non-ENSO' 'strong'
and 'weak' monsoon years.
In choosing 'non-ENSO' monsoon
years, the criterion of > 1 s.d (or < -1 s.d) was relaxed
to > 0.5 s.d (or < -0.5 s.d).
The time series of the Nino 3.4 SST index values during the period of our study is shown in figure 4. We classify the ENSO events as weak or strong following Bulic and Brancovic [29]. The weak ENSO refers to the Nino 3.4 index from 1.0°C to 1.5°C, and the strong ENSO refers to the Nino 3.4 index larger than 1.5°C. Our analysis is based on composites of fourteen weak La Nina events, six strong La Nina events, twelve weak El Nino events and six strong El Nino events as shown in figure 4 and table 2.