Indonesian fires of 1997-2015: connection with El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)

The fires observed during 1997-2015 in the tropical forests and peatlands of equatorial Asian regions, such as Indonesia, generated heavy smoke clouds that not only exerted adverse impacts on the air quality, both locally and regionally, but also interacted with the climate system through atmospheric circulation and radiative forcing. It is well observed and documented that intensive Indonesian fires are usually associated with El Niño years, such as those of 1997, 2002, 2006 and 2015. However, intensive Indonesian fire events did not occur in the 2009 El Niño year which was even stronger than 2006, contrary to expectations. This exception indicates that we have not fully understood the question: "How does El Nino affect the strength of Indonesian fires? ". Our study revealed why there were no large Indonesian fire events in 2009 by examining the relationship of Indian Ocean Dipole (IOD) with El Niño. IOD is proved to be another critical factor (besides El Niño) to modulate the occurrence of intensive fire events in Indonesia The outcome of this study will improve the predictability of the future Indonesian fires associated with drought, by connecting the occurrence of Indonesian fires with both El Niño and IOD that could be predicted in advance.