the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Estimation of Biomass Burning Emission of NO2 and CO from 2019–2020 Australia Fires Based on Satellite Observations
- 1Department of Agronomy, Kansas Climate Center, Kansas State University, Manhattan, KS, 66502, USA
- 2NASA Langley Research Center, Hampton, VA, 23618, USA
- 3Department of Geography and Geospatial Sciences, Kansas State University, Manhattan, KS, 66502, USA
- 1Department of Agronomy, Kansas Climate Center, Kansas State University, Manhattan, KS, 66502, USA
- 2NASA Langley Research Center, Hampton, VA, 23618, USA
- 3Department of Geography and Geospatial Sciences, Kansas State University, Manhattan, KS, 66502, USA
Abstract. The bushfires that occurred in Australia in late 2019 and early 2020 were unprecedented in terms of their scale, intensity, and impacts. Using nitrogen dioxide (NO2) and carbon monoxide (CO) data measured by the Tropospheric Monitoring Instrument (TROPOMI), together with fire counts and fire radiative power (FRP) from MODIS, we analyzed the temporal and spatial variation of NO2 and CO column densities over three selected areas covering savanna and temperate forest vegetation. The ΔNO2 / ΔCO emission ratio and emission factor were also estimated. The ΔNO2 / ΔCO emission ratio was found to be 1.5 ± 1.2 for temperate forest fire and ranged from 2 ± 1.3 to 2.8 ± 1.8 for savanna fire. For savanna and temperate forest fires, satellite-derived NOx emission factors are 1.29 g kg-1 and 1.2 g kg-1 separately, while CO emission factors are 62.34 and 112.5 g kg-1. This study demonstrates that the large-scale emission ratio from the TROPOMI satellite for different biomass burnings can help identify the relative contribution of smoldering and flaming activities and their impacts on the regional atmospheric composition and air quality.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(1759 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
Journal article(s) based on this preprint
Nenghan Wan et al.
Interactive discussion
Status: closed
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RC1: 'Comment on acp-2022-447', Anonymous Referee #1, 19 Sep 2022
The study presents an analysis of satellite-measured CO and NO2 for the Australian 2019/2020 wildfire season using TROPOMI. The authors use the satellite-measured enhancement ratio near fires in southeast Australia, as well as for two northern Australian regions, to derive a proxy for combustion efficiency and calculate emission factors for large regions.
Overall the manuscript is well written and the analysis rigorous. Satellites provide an opportunity to determine emissions over larger areas than field campaigns or laboratory studies. The results and methodologies presented here have the potential to be applied to other regions and for other years. I have several comments to be addressed below, roughly in order of importance.
Main Comments:
1. The temporal period (November 2019- January 2020) chosen was aligned with the maximum burning in southeast Australia (Area 3). The fire season in Areas 1 and 2 are usually different to Area 3. The peak burning season in Area 1 and Area 2 occur in September – October, while Area 1 usually peaks December – January (Russell-Smith et al., 2007, https://doi.org/10.1071/WF07018). The peak wildfire emissions in Areas 1 and 2 were likely not captured in this study. Consequently, the comparison of Area 3 and Areas 1 and 2 (e.g. on page 9) compares a mid-burning season (SE) with a late-burning season (NW). Additionally, 2019 was an an usually low year for biomass burning in Northern Australia, so the season may not be representative of the region on average. Please clarify the motivation for including Areas 1 and 2 and the timing in this study.
2. L172: Concerning the appropriateness of an 850 hPa average height when aerosol layer height is unavailable. Please explain why it is appropriate to use 850 hPa as an average for all three regions. There were some very large pyrocumulus events in the 2019/2020 fire season. For example, does the average change appreciably if the pyrocumulus events are removed? Additionally, is 850 hPa used for Northern Australia, where pyrocumulus are rarer?
3. Please clarify why it is appropriate to compare total column CO and tropospheric NO2? For example, can you be confident you are capturing the same air masses.
4. Section 3.1
- Please describe or clarify how recirculating plumes are avoided in emission ratio calculations.
- L183-184: Please clarify what specifically was used to determine upwind direction – a visual inspection of aerosol layer height, CO maps, ERA wind direction?
- CO and NO2 also have strong anthropogenic sources – a comment about how this is accounted for would be valuable.
5. L191-192: Were there fewer fires in Northern Australia during 2018/2019 compared to 2019/2020?
6. Section 3.2: I seem to have missed the description of the rotation of wind directions to align the pollution plume, as shown in Figure 2 c).
7. Describe the “grand” or overall emissions ratio calculation in section 3.1.
8. Figure 9 – please add a description of the different color lines to the figure.
9. Why was the Griffin et al. (2021) aerosol correction not applied to TROPOMI NO2 retrievals here? It seems like this would improve the results for the NO2 emission ratios.
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Technical Corrections:
L109: seldom → sparse
L306: does “grand emission ration” mean “overall emission ratio”?
L341: filed → field
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AC1: 'Reply on RC1', Xiaomao Lin, 23 Nov 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-447/acp-2022-447-AC1-supplement.pdf
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RC2: 'Comment on acp-2022-447', Anonymous Referee #2, 28 Sep 2022
Overall, this is an excellent research article. In addition to the suggested revisions of the other reviewer, I would like to see improvement in the abstract as well as the summary and conclusions, which are a bit thin on the important implications of your research. For instance, you make the following statement in the summary and conclusions: "Our study on both savanna and temperate forest fire emissions demonstrates the capability and limitations of TROPOMI data for the study of the regional variability of combustion characteristics and their impacts on regional atmospheric composition and air quality." You make a similar comment in the abstract. This statement may be accurate, but I would like you to elaborate on this statement, including on how your technique may be applied to other world regions. As another example, you say: "These differences could be traced back to different measurement techniques used, their spatial resolutions, nonlinear sensitivities to gas densities in the boundary layer, and larger NO2 natural variability due to its short lifetime, all of which suggest that further validation of satellite products and investigations of more cases are required." Could you suggest additional validation that would be most helpful to this end? How many cases are required? My recommendation is to revisit the abstract and summary and conclusions with an eye for elaborating on the broader implications of your research.
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AC2: 'Reply on RC2', Xiaomao Lin, 23 Nov 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-447/acp-2022-447-AC2-supplement.pdf
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AC2: 'Reply on RC2', Xiaomao Lin, 23 Nov 2022
Peer review completion
Interactive discussion
Status: closed
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RC1: 'Comment on acp-2022-447', Anonymous Referee #1, 19 Sep 2022
The study presents an analysis of satellite-measured CO and NO2 for the Australian 2019/2020 wildfire season using TROPOMI. The authors use the satellite-measured enhancement ratio near fires in southeast Australia, as well as for two northern Australian regions, to derive a proxy for combustion efficiency and calculate emission factors for large regions.
Overall the manuscript is well written and the analysis rigorous. Satellites provide an opportunity to determine emissions over larger areas than field campaigns or laboratory studies. The results and methodologies presented here have the potential to be applied to other regions and for other years. I have several comments to be addressed below, roughly in order of importance.
Main Comments:
1. The temporal period (November 2019- January 2020) chosen was aligned with the maximum burning in southeast Australia (Area 3). The fire season in Areas 1 and 2 are usually different to Area 3. The peak burning season in Area 1 and Area 2 occur in September – October, while Area 1 usually peaks December – January (Russell-Smith et al., 2007, https://doi.org/10.1071/WF07018). The peak wildfire emissions in Areas 1 and 2 were likely not captured in this study. Consequently, the comparison of Area 3 and Areas 1 and 2 (e.g. on page 9) compares a mid-burning season (SE) with a late-burning season (NW). Additionally, 2019 was an an usually low year for biomass burning in Northern Australia, so the season may not be representative of the region on average. Please clarify the motivation for including Areas 1 and 2 and the timing in this study.
2. L172: Concerning the appropriateness of an 850 hPa average height when aerosol layer height is unavailable. Please explain why it is appropriate to use 850 hPa as an average for all three regions. There were some very large pyrocumulus events in the 2019/2020 fire season. For example, does the average change appreciably if the pyrocumulus events are removed? Additionally, is 850 hPa used for Northern Australia, where pyrocumulus are rarer?
3. Please clarify why it is appropriate to compare total column CO and tropospheric NO2? For example, can you be confident you are capturing the same air masses.
4. Section 3.1
- Please describe or clarify how recirculating plumes are avoided in emission ratio calculations.
- L183-184: Please clarify what specifically was used to determine upwind direction – a visual inspection of aerosol layer height, CO maps, ERA wind direction?
- CO and NO2 also have strong anthropogenic sources – a comment about how this is accounted for would be valuable.
5. L191-192: Were there fewer fires in Northern Australia during 2018/2019 compared to 2019/2020?
6. Section 3.2: I seem to have missed the description of the rotation of wind directions to align the pollution plume, as shown in Figure 2 c).
7. Describe the “grand” or overall emissions ratio calculation in section 3.1.
8. Figure 9 – please add a description of the different color lines to the figure.
9. Why was the Griffin et al. (2021) aerosol correction not applied to TROPOMI NO2 retrievals here? It seems like this would improve the results for the NO2 emission ratios.
------------------------------------------------------
Technical Corrections:
L109: seldom → sparse
L306: does “grand emission ration” mean “overall emission ratio”?
L341: filed → field
-
AC1: 'Reply on RC1', Xiaomao Lin, 23 Nov 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-447/acp-2022-447-AC1-supplement.pdf
-
RC2: 'Comment on acp-2022-447', Anonymous Referee #2, 28 Sep 2022
Overall, this is an excellent research article. In addition to the suggested revisions of the other reviewer, I would like to see improvement in the abstract as well as the summary and conclusions, which are a bit thin on the important implications of your research. For instance, you make the following statement in the summary and conclusions: "Our study on both savanna and temperate forest fire emissions demonstrates the capability and limitations of TROPOMI data for the study of the regional variability of combustion characteristics and their impacts on regional atmospheric composition and air quality." You make a similar comment in the abstract. This statement may be accurate, but I would like you to elaborate on this statement, including on how your technique may be applied to other world regions. As another example, you say: "These differences could be traced back to different measurement techniques used, their spatial resolutions, nonlinear sensitivities to gas densities in the boundary layer, and larger NO2 natural variability due to its short lifetime, all of which suggest that further validation of satellite products and investigations of more cases are required." Could you suggest additional validation that would be most helpful to this end? How many cases are required? My recommendation is to revisit the abstract and summary and conclusions with an eye for elaborating on the broader implications of your research.
-
AC2: 'Reply on RC2', Xiaomao Lin, 23 Nov 2022
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-447/acp-2022-447-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Xiaomao Lin, 23 Nov 2022
Peer review completion
Journal article(s) based on this preprint
Nenghan Wan et al.
Nenghan Wan et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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