b. The relationship of an annual rainfall and the ocean
indices
1. The annual rainfall and the summer monsoon
The mean annual rainfall had relationship with 2 indices
as IMI and WNPMI and it was found that relationships were R
= 0.421 and R = 0.468, respectively. It represented that a mean
annual rainfall was in relationship with a WNPMI more than a
IMI or annual rainfall in the Northeast was effected from the
Pacific Ocean more than the Indian Ocean of monsoon. The
focus was on prominent months of interactive as June, August
and September of WNPMI as the first rainy timeframe was
from May to July and second rainy timeframe was August to
October in the Northeast rainy season (Mongkolsawat et al.,
2010) [18]. It was found that the WNPMI of June and August
was the lowest in 1998, (Figure 3a) and lowest WNPMI was
-1.717, and also lowest of mean annual rainfall was 1,187 mm.
in the year 1998. While the highest of average WNPMI was
not corresponded with annual rainfall in 2009, it was because
rainfall may depend on other indices or other factors. But
mostly, average WNPMI had corresponding with annual
rainfall in period studies (Figure 3b). It shows the relationship
of rainfall in the Northeast w