The rainfall variability of each season over Thailand was exhibited by the EOF technique. The most dominant mode of each season the variability accounts for 47.5%, 24.1% , 31.0% , and 21.3% of the total variance respectively. It can explain the variation of the long term average of rainfall during the season of over Thailand.
The correlation analysis suggest that the Nino3,Nino3.4 SST index influence rainfall variability of each season over Thailand. Especially, the most correlation between the Niño3.4 with rainfall during March April and May (summer).
The rainfall variability during boreal winter (December to February) over the Indochina peninsula was exhibited by the EOF technique. The leading mode of the variability accounts 42.6% of the total variance, and shows the interannual variation. Its spatial distribution presents large rainfall variation over the southern part over the Indochina and the central part of Vietnam, whereas its temporal variation shows the correlation to the SST anomalies, particularly in the Pacific Ocean
The main results found in this study may be summarized as follows. In our EOF analysis of rainfall over Thailand during the period 1971-2010 the most dominant mode, accounting for 21.6% of the total variance, had a spatial pattern with the same sign (positive) over almost all of Thailand. Consequently, when the PC was positive there was more rainfall than normal and when the PC was negative there was less rainfall than normal almost everywhere. An exception to this general result occurs in the south at latitudes below 9°N.