Abstract
Extreme fires in the peatlands of South East (SE) Asia are arguably the world’s greatest biomass burning events, resulting in some of the worst ambient air pollution ever recorded (PM10 > 3000 µg·m−3). The worst of these fires coincide with El Niño related droughts, and include huge areas of smouldering combustion that can persist for months. However, areas of flaming surface vegetation combustion atop peat are also seen, and we show that the largest of these latter fires appear to be the most radiant and intensely smoke-emitting areas of combustion present in such extreme fire episodes. Fire emissions inventories and early warning of the air quality impacts of landscape fire are increasingly based on the fire radiative power (FRP) approach to fire emissions estimation, including for these SE Asia peatland fires. “Top-down” methods estimate total particulate matter emissions directly from FRP observations using so-called “smoke emission coefficients” [Ce; g·MJ−1], but currently no discrimination is made between fire types during such calculations. We show that for a subset of some of the most thermally radiant peatland fires seen during the 2015 El Niño, the most appropriate Ce is around a factor of three lower than currently assumed (~16.8 ± 1.6 g·MJ−1 vs. 52.4 g·MJ−1). Analysis indicates that this difference stems from these highly radiant fires containing areas of substantial flaming combustion, which changes the amount of particulate matter emitted per unit of observable fire radiative heat release in comparison to more smouldering dominated events. We also show that even a single one of these most radiant fires is responsible for almost 10% of the overall particulate matter released during the 2015 fire event, highlighting the importance of this fire type to overall emission totals. Discriminating these different fires types in ways demonstrated herein should thus ultimately improve the accuracy of SE Asian fire emissions estimates derived using the FRP approach, and the air quality modelling which they support.
Highlights
In the second half of the 20th Century, changing land management practices in the lowland tropical swamp forests of equatorial South East (SE) Asia led many to be degraded from their natural forest-covered, persistently waterlogged state [1,2,3,4,5]
Our analysis focused on a series of the most radiant fires burning in Indonesian peatlands fire fronts of the type shown in Figure 1, and in fuels consisting of both surface vegetation as well as during the 2015 El Niño (September and October 2015)
The difference is primarily attributed to the fact that the highly radiant fires focused upon include significant flaming activity in surface fuels, such flaming vegetation fire atop burning peat is significantly higher than for smouldering peat fires alone, further increasing the amount of particulate matter they release per unit time
Summary
In the second half of the 20th Century, changing land management practices in the lowland tropical swamp forests of equatorial South East (SE) Asia led many to be degraded from their natural forest-covered, persistently waterlogged state [1,2,3,4,5]. Sensors 2020, 20, x FOR PEER REVIEW enough enough to to burn burn at at times times of of low low rainfall rainfall in in many many of of these these deforested deforested and and drained drained areas, areas, leading leading to to substantial increases in the region’s susceptibility to extreme landscape fire— during substantial increases in the region’s susceptibility to extreme landscape fire— during the the periodic El El Niño–Southern. During the extreme periodic droughts droughtsbrought broughtononbyby. An overwhelming number of landscape fires occurred in the tropical peatlands of Kalimantan. 2015 El Niño, an overwhelming number of landscape fires occurred in the tropical peatlands of and Sumatraand during.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
