In view of the relationship between the variability of rainfall during each season represented by PC1 to SST anomalies in various months, we perform lead-lag correlation analysis to further investigate. The SST anomalies in Pacific Ocean were averaged, and used them to determine the relationships with the variability of rainfall over Thailand. Whereas, Nino3 and Nino3.4 area representing ENSO phenomenon (Trenberth and Stepaniak, 2001) was used to determine the lag correlations. The positive correlation means that the increasing (decreasing) of SST anomalies in that area related to rising (reducing) of the rainfall variability magnitude indicating more (less) rainfall over Thailand (Sirapong, ea.la, 2014). While,the negative correlation means that the increasing (decreasing) of SST anomalies in that area related to reducing (rising) of the rainfall variability magnitude indicating more (less) rainfall over Thailand.
To confirm the association between PC1 and SST of each season in the equatorial Pacific Ocean, the correlation analysis at to 11month lags was performed. The result is shown in Figure 1 and 2. While, the correlation of lag time between the rainfall anomalies and Niño 3, Niño 3.4 SST index of each season shown in Table 1 and 2.