Connecting Indonesian Fires and Drought with the Type of El Niño and Phase of the Indian Ocean Dipole During 1979‐2016

Indonesian fires are well known for their adverse impact on regional air quality and climate because they release massive amounts of greenhouse gases and aerosols into the atmosphere. Fire activities in Indonesia are recognized as a result of the interplay of land use practices and climate variability. The objective of our study is to advance the understanding of the role of climate variability on modulating Indonesian fire activity. This study advances the previous understanding of the role of climate variability on Indonesian fire activity, by considering (i) the presence of different types (or location) of El Niño events in the Pacific Ocean, and (ii) the interaction between El Niño and the Indian Ocean Dipole (IOD) phenomena.

As a result, we find that more intensive and prolonged Indonesian fires occur during canonical El Niño events when the location of maximum SST anomaly is near the eastern Pacific accompanied with a positive phase of IOD (e.g., in 2006), shown as the left column in the Figure. In contrast, weaker Indonesian drought and fires likely occur in the El Niño events when the location of maximum SST anomaly is near the central Pacific accompanied by a weakly positive or even negative phase of the IOD instead (e.g., in 2009), shown as the right column in the Figure. The outcome of this study can be applied to drought early warning, fire management and air quality forecast in Indonesia and adjacent areas by identifying the type (or location) of El Niño and the phase (or sign) of IOD in advance. More details can be found at JGR-atmosphere (https://doi.org/10.1029/2018JD028402).

Figure Caption: The spatial distribution of the composites of variables during August–September–October in Indonesia and adjacent area: (a) SSTA, (b) Precip, (c) DC, and (d) CarbonEmis in three El Niño-IOD groups, namely the EP group (left column), CP El Niño with IOD in phase group (middle column), and CP El Niño with IOD out of phase group (right column). The rectangular brown boxes represent the southern Sumatra and southern Kalimantan, respectively, with the area-averaged value over each box labeled at the top of the map in vertical alignment with the corresponding box. The domain is bounded by 90 to 140°E and 15°S to 10°N. The horizontal dotted line in each map represents the equator. SSTA = sea surface temperature anomaly; Precip = total precipitation rate; DC = drought code; CarbonEmis = carbon emission; EP = Eastern Pacific; CP = Central Pacific; IOD = Indian Ocean Dipole; CP-IOD-inphase = CP type of El Niño with positive IOD; CP-IOD-outphase = CP type of El Niño with negative IOD.