The rainfall characteristics over Indonesia were investigated using the GSOD precipitation data for
a 26-year period from January 1985 to August 2010. Based on the spatial correlations between the
five-month running mean of the precipitation and regional climate indices, the rainfall characteristics
in eastern Indonesia, including the Papua region, the Maluku Islands, Sulawesi Island, eastern
Kalimantan Island, and eastern Java Island, were highly correlated with the ENSO and PDO indices,
with high rainfall during strong La Niña episodes and cool PDO phases when the western Pacific
Ocean is relatively warmer. In central Indonesia, the Malaysian-Australian monsoon plays a dominant
role in the rainfall characteristics and results in distinctive seasonal variations, similar to the findings
of Aldrian and Djamil [53]. In western Indonesia, the rainfall in the southern and southeastern portions
of Sumatra Island and southern Java Island that face the Indian Ocean was negatively correlated with
the DMI, indicating high rainfall during negative IOD periods when the eastern Indian Ocean is
relatively warmer. Interestingly, the rainfall in northwestern Sumatra Island was positively correlated
with the DMI, in contrast to the finding for southern Sumatra.