the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Jun 2025
Technical Note: Identifying Biomass Burning Emissions During ASIA-AQ Using Greenhouse Gas Enhancement Ratios
Abstract. Biomass burning (BB) is a primary source of atmospheric chemistry reactants, aerosols, and greenhouse gases. Smoke plumes have air quality impacts local to the fire itself and regionally via long distance transport. Open burning of agriculture fields in Southeast Asia leads to frequent seasonal occurrences of regional BB-induced smoke haze and long-range transport of BB particles via the northeast monsoon. The Airborne and Satellite Investigation of Asian Air Quality (ASIA-AQ) campaign visited several areas including the Philippines, South Korea, Thailand, and Taiwan during a time of agricultural burning. This campaign consisted of airborne measurements on the NASA DC-8 aircraft aimed to validate observations from South Korea's Geostationary Environment Monitoring Spectrometer (GEMS) and to address local air quality challenges. We developed a method that used a combination of BB markers to identify ASIA-AQ DC-8 data influenced by BB and flag them. Specifically, we used rolling slope enhancement ratios of CO/CO2 and CH4/CO along with mixing ratios of CH3CN, HCN, and CO, and particle scattering coefficient measurements. The flag was triggered when a combination of these variables exceeded a flight specific threshold. We found varying levels of BB-influence in the areas studied, with data flagged for BB being <1 % for the Philippines and Korea, and <2 % for Taiwan, but 19 % for Thailand. Our method for flagging ASIA-AQ BB-affected data can be used to focus additional analyses of the ASIA-AQ campaign such as pairing with back-trajectories, satellite hotspot products, and microphysical aerosol characteristics.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-2602', Anonymous Referee #1, 09 Sep 2025
This paper utilizes airborne measurements to determine the presence of biomass burning in southeast asia. The detailed analysis of gas- and particulate-phase tracers provides a robust means to identify sources. They then analyze the location and sources of the plumes and the properties of the aerosol emitted. All told, this is a robust analysis and beneficial to the study of biomass burning and pollution in the region. A few major edits are needed however:
Major Issues
- Line 133-134: what are these “inefficient combustion processes other than biomass burning” and how would addition of a third variable remove these. For instance, what type of incomplete combustion due you think would produce CO and particles but not HCN or a high CO/CO2. I would think this might be due to mixing of different sources (maybe that are high in CO2).
- Line 130-139: need more discussion on how this was decided: why only two variables must be over the threshold, why a flight-by-flight determination of a threshold (wouldn’t a campaign threshold be better). Was a sensitivity analysis performed?
- Figure 5: more clearly identify in the figure itself (not the caption) – that the row represents the day. So above A/E/I it should say March 16 (or something like that).
- Figure 5: If I am reading this correctly: for figure 5A: roughly 27% of the data collected over Thailand was BB, and about 4% of all data points were BB and below 1 km. But, what we don’t know from this figure is how much time was spent below 1 km. If only 4% of the time was spent below 1 km, then ALL of the low level data is tagged as BB. But, if 40% of the flight time was spent below 1 km, then 10% of the low level data is tagged as BB. Would separating out each of the columns into two columns make sense?
- Figure 8a & 8b: why are there no measurements for the BB data below ~12 nm? Weren’t the BB and unflagged using the same instrument s there should be this data.
Minor Issues & Typos
- Line 22: I am not sure how apparent “flag them” is maybe clarify by stating “flag them for further analysis”
- Line 33: as written it appears you are stating CO is a greenhouse gas (which it is not) because the first two sentences are about GHG emissions. Possibly remove CO from this sentence and put it in its own sentence stating something like “CO (while not a greenhouse gas) is also emitted from urban sources…”
- Line 59: “(DiGangi et al., 2025) adapted” should be “DiGangi et al. (2025) adapted”
- Line 66: “CO mixing ratio” should be “CO” as you already state you are talking about mixing ratios
- Line 103-104: “uncorrelated and, slopes” should be “uncorrelated, and slopes” or “uncorrelated and slopes”
- Line 137: change “20240316” to an acceptable date format
- Table 1: should note that the definition of threshold changes. For CH4/CO, values below5 are BB. For everything else, values above the threshold are BB.
- Line 281 & 283: I think “and 25 2024.” Should be “and 25, 2024.”
- Figure 2: caption should include which quadrant represents BB – in this case (upper left)?
- Figure 8a: I believe you can put both of the curves on the same scale and still see them so it is not as complicated a figure.
Citation: https://doi.org/10.5194/egusphere-2025-2602-RC1 -
RC2: 'Comment on egusphere-2025-2602', Anonymous Referee #2, 09 Sep 2025
Jason Miech and co-authors present a well written manuscript describing an approach at tagging biomass burning air parcels. Their method builds on prior work using short term changes in gas phase species to identify significant biomass burning compositional influence. Both the method refinements and resultant application are important. I recommend acceptance for publication after addressing a minor issue.
In the discussion of Figures 5A and 5B in Section 3.2.1, it would be helpful to add a note indicating the relative number of Thailand low altitude BB-flagged points to both 5A and 5B because it is difficult for the reader to visually discern the difference.
Citation: https://doi.org/10.5194/egusphere-2025-2602-RC2
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