Atmospheric CH<sub>4</sub> and CO<sub>2</sub> enhancements and biomass burning emission ratios derived from satellite observations of the 2015 Indonesian fire plumes

Abstract

Abstract. The 2015-2016 strong El Niño event has had a dramatic impact on the amount of Indonesian biomass burning, with the El Niño-driven drought further desiccating the already-drier-than-normal landscapes that are the result of decades of peatland draining, widespread deforestation, anthropogenically driven forest degradation and previous large fire events. It is expected that the 2015-2016 Indonesian fires will have emitted globally significant quantities of greenhouse gases (GHGs) to the atmosphere, as did previous El Niño-driven fires in the region. The form which the carbon released from the combustion of the vegetation and peat soils takes has a strong bearing on its atmospheric chemistry and climatological impacts. Typically, burning in tropical forests and especially in peatlands is expected to involve a much higher proportion of smouldering combustion than the more flaming-characterised fires that occur in fine-fuel-dominated environments such as grasslands, consequently producing significantly more CH 4 (and CO) per unit of fuel burned. However, currently there have been no aircraft campaigns sampling Indonesian fire plumes, and very few ground-based field campaigns (none during El Niño), so our understanding of the large-scale chemical composition of these extremely significant fire plumes is surprisingly poor compared to, for example, those of southern Africa or the Amazon.Here, for the first time, we use satellite observations of CH 4 and CO 2 from the Greenhouse gases Observing SATellite (GOSAT) made in large-scale plumes from the 2015 El Niño-driven Indonesian fires to probe aspects of their chemical composition. We demonstrate significant modifications in the concentration of these species in the regional atmosphere around Indonesia, due to the fire emissions.Using CO and fire radiative power (FRP) data from the Copernicus Atmosphere Service, we identify fire-affected GOSAT soundings and show that peaks in fire activity are followed by subsequent large increases in regional greenhouse gas concentrations. CH 4 is particularly enhanced, due to the dominance of smouldering combustion in peatland fires, with CH 4 total column values typically exceeding 35 ppb above those of background "clean air" soundings. By examining the CH 4 and CO 2 excess concentrations in the fire-affected GOSAT observations, we determine the CH 4 to CO 2 (CH 4 / CO 2 ) fire emission ratio for the entire 2-month period of the most extreme burning (SeptemberOctober 2015), and also for individual shorter periods where the fire activity temporarily peaks. We demonstrate that the overall CH 4 to CO 2 emission ratio (ER) for fires occurring in Indonesia over this time is 6.2 ppb ppm −1 . This is higher than that found over both the Amazon (5.1 ppb ppm −1 ) and southern Africa (4.4 ppb ppm −1 ), consistent with the Indonesian fires being characterised by an increased amount of smouldering combustion due to the large amount of organic soil (peat) burning involved. We find the range of our satellitePublished by Copernicus Publicati...

Long‐Lead Prediction of the 2015 Fire and Haze Episode in Indonesia

“…The strength of the 2015 El Niño was comparable to the very strong 1997 event (L'Heureux et al, 2017) to intensify the drying effects of El Niño over western Indonesia (Koplitz et al, 2016). The bulk of the emissions are due to burning in degraded peatlands (Levine, 1999;Page et al, 2002;Parker et al, 2016). Fires lit on the surface to clear agricultural and logging debris are more likely to escape and can spread underground into the peat.…”

Temperature and burning history affect emissions of greenhouse gases and aerosol particles from tropical peatland fire

“…Furthermore, air pollution induced by haze has impacted human health in the region [Kunii et al, 2002;Marlier et al, 2013]. Studies on emissions of greenhouse gases as well as aerosol particles from tropical peat burning are necessary; however, only limited research has been reported and the results are variable [Christian et al, 2003;Stockwell et al, 2014;Parker et al, 2016]. For instance, emission ratios of CH 4 and CO 2 (ΔCH 4 /ΔCO 2 ) are summarized in Table 1.…”

“…However, impacts of different burning stages of peat on emissions of aerosol particles and greenhouse gases have not been investigated. [Parker et al, 2016] In addition to heating temperature, the burning process is also affected by the history of previous burning. For instance, TG-DTA analysis of humic acid extracted from peat sampled at a burned area in Kalimantan does not have a significant peak corresponding to the temperature of charcoal formation, while it still has a strong signal in the temperature range of charcoal burning [Yustiawati et al, 2015].…”

Chemical characterization of fine particulate matter emitted by peat fires in Central Kalimantan, Indonesia, during the 2015 El Niño

“…Notably, even in non-El Niño years, peat burning remains an important source of biomass burning emissions in Southeast Asia . The 2015 peatland fire episode that occurred SeptemberNovember 2015 occurred during an El Niño year and was reported as the strongest peatland fire episode since 1997-1998 (Parker et al, 2016;Koplitz et al, 2016;Huijnen et al, 2016). The 2015 fires burned ∼ 1 million ha of tropical forests and peatlands in Indonesia, releasing ∼ 0.2 Pg C of carbon to the atmosphere (Huijnen et al, 2016).…”