the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Feb 2024
Investigating the vertical extent of the 2023 summer Canadian wildfire impacts with satellite observations
Abstract. Pyrocumulonimbus clouds (pyroCbs) generated by intense wildfires can serve as a direct pathway for the injection of aerosols and gaseous pollutants into the lower stratosphere, resulting in significant chemical, radiative, and dynamical changes. Canada experienced an extremely severe wildfire season in 2023, with a total area burned that substantially exceeded those of previous events known to have impacted the stratosphere (such as the 2020 Australian fires). This season also had record-high pyroCb activity, which raises the question of whether the 2023 Canadian event resulted in significant stratospheric perturbations. Here, we investigate this anomalous wildfire season using retrievals from two satellite instruments, ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) and OMPS LP (Ozone Mapping and Profile Suite Limb Profiler), to determine the vertical extents of the wildfire smoke along with chemical signatures of biomass burning. These data show that smoke primarily reached the upper troposphere but only a nominal amount managed to penetrate the tropopause. Only one ACE-FTS occultation captured elevated concentrations of biomass burning products in the lower stratosphere on July 30th, and back and forward trajectories place the source fire in the Yukon. However, OMPS LP aerosol measurements indicate that any smoke that made it past the tropopause did not last long enough to significantly perturb stratospheric composition. While this work focuses on Canadian wildfires given the extensive burned area, pyroCbs at other longitudes (e.g. Siberia) are also captured in the compositional analysis. These results highlight that despite the formation of many pyroCbs in major wildfires, those capable of penetrating the tropopause are extremely rare; this in turn means that even a massive area burned is not necessarily an indicator of stratospheric effects.
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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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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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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-353', Michael Fromm, 22 Mar 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-353/egusphere-2024-353-RC1-supplement.pdf
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RC2: 'Comment on egusphere-2024-353', Anonymous Referee #3, 13 Jul 2024
This study uses satellite remote sensing datasets to examine the vertical extents of wildfire smoke, along with chemical signatures of biomass burning, during the record fire season of 2023 in Canada. This topic has high relevance for a broad community interested in the role of large wildfires in a warming climate system. However, several issues must be addressed prior to publication in ACP, which amount to a major revision.
While I understand the focus on stratospheric impacts (or the lack thereof), it would be nice to have a bit more focus on the potential implications of having so much smoke in the upper-troposphere. Can we say anything about what this might mean for future climate scenarios?
More information is needed in the methods section on how tropopause altitudes were calculated. This should be a stand-alone section. How do the methods used here to obtain tropopause altitude compare with previous studies that used other methods and data sources. There is currently only one sentence on using temperature profiles from ACE-FTS to derive tropopause altitude. How are these profiles derived? How does the accuracy compare with reanalysis or radiosonde temperature profiles? Have any previous studies used ACE-FTS to obtain tropopause altitudes?
Some of the figures in this paper present results with tropopause relative altitude while others use absolute altitude. It might be best to use one of these methods in all figures for consistency. In this case, tropopause relative altitude seems like the better choice?
The decision to omit MLS from the analysis in this paper needs more clarification. It seems that MLS and ACE-FTS have their own sets of strengths and weaknesses for a study like this. So, using them in combination would likely have benefits. MLS data have also been used in previous pyroCb plume studies. At minimum, the authors should cite some of this previous work as part of a more robust justification for why MLS is not used.
Fig. 1: Please provide more discussion on the tropopause altitude discrepancy in August. This relates to my tropopause methods comment above. Perhaps run some comparisons with tropopause altitudes derived from reanalysis data, such as MERRA-2. It may also be helpful to include a range or standard deviation marker for the tropopause, along with the mean.
It seems like the signal from the 2017 PNE is missing in the September panel (blue dashed curve)? I would expect to see a significant enhancement above the tropopause.
Fig 5: This might be more informative as an anomaly plot relative to the OMPS data record…or add a second panel with this anomaly information.
Fig. 6 and S4: The trajectory analysis can be improved. In Fig. 6, why was it decided to use multiple time intervals and constrain the trajectories to three days? The time of the ACE-FTS profile should be exact…there is no need for other times. This smoke could have originated from pyroCb activity more than three days before the ACE-FTS observations time. I recommend extending the duration of the trajectories to see if other fires in Canada might have contributed. For Fig. S4, the timing of the trajectories is also very questionable, when considering that a pyroCb event usually lasts for only a few hours. You can look at satellite imagery of the event to get a sense of how long it persisted, and thus the duration of the smoke injection window to launch trajectories from.
Fig. 7 legend: please make it clear which profile is 2023 vs. the 2017 PNE (red vs. black). That terminology is easier to digest than the profile numbers. Put the profile numbers in the caption.
Fig. 8 and S5: It took me a long time to digest what’s going on in these figures. The values of the mean curves in the time series are near the top of the color bar scale in the shaded plots when smoke is present, which doesn’t make sense. Are the curves the maximum value? In Fig. S5, the caption notes that different layers are used for these plots, but in Fig. 8 they use the same layer? Regardless, this analysis is critical to the narrative. It should all show in the main paper…not the supplement…after the errors are fixed.
Citation: https://doi.org/10.5194/egusphere-2024-353-RC2 -
RC3: 'Comment on egusphere-2024-353', Anonymous Referee #4, 26 Jul 2024
General comments:
The paper presents an interesting analysis on the presence of particles in the stratosphere from 2023 summer Canadian wildfires, using some satellite data. Nevertheless, the paper is too short, some works on the same subject need to be considered for an improved discussion, and perhaps others sources of data should be analyzed before concluding that such smoke particles from wildfire are rare in the stratosphere.
The paper need a major revised before it can be considered for publication.
Specific comments:
The authors speak of vertical extend, but no vertical profile of particles in the stratosphere are presented. So, the title of the paper must be changed, or real aerosol vertical data in the stratosphere, perhaps from different instrumental sources, must be considered.
Line 55 : Some publications are missing, in particular the ones showing that large amount of soot particles can be injected in the stratosphere during wildfire events. Also, others works are available on the vertical extend of smokes in the stratosphere. The authors must rewrite this paragraph, considering the recent results on the stratospheric solid particles and on vortex resulting from wildfires. Here some examples of papers:
- Sellitto, Pasquale & Belhadji, Redha & Cuesta, Juan & Podglajen, Aurélien & Legras, Bernard. (2023). Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating. 10.5194/egusphere-2023-1067.
- Lestrelin, Hugo & Legras, Bernard & Podglajen, Aurélien & Salihoglu, Mikail. (2021). Smoke-charged vortices in the stratosphere generated by wildfires and their behaviour in both hemispheres: comparing Australia 2020 to Canada 2017. Atmospheric Chemistry and Physics. 21. 7113-7134. 10.5194/acp-21-7113-2021.
- Renard, Jean-Baptiste, Berthet, Gwenaël, Levasseur-Regourd, Anny-Chantal , Beresnev, S. , Miffre, Alain , Rairoux, Patrick , Vignelles, Damien , Jegou, F.. (2020). Origins and Spatial Distribution of Non-Pure Sulfate Particles (NSPs) in the Stratosphere Detected by the Balloon-Borne Light Optical Aerosols Counter (LOAC). Atmosphere. 11. 10.3390/atmos11101031.
Can the authors provide error bars for the concentration in Figure 3 and Figure 4? Without such error bars, it is not possible to assess the reality of the detections.
Line 170-174 : This conclusion seems to be in contradiction with other works on this subject. The author must improve the bibliography and explain how their results can be compared to previous works and why they could differ.
Line 180: Figure 5 do not show the vertical profile of aerosol extinction, so how the authors can speak of a “significant decrease in signal past 11.5 km”?
Citation: https://doi.org/10.5194/egusphere-2024-353-RC3 -
AC1: 'Comment on egusphere-2024-353', Selena Zhang, 28 Aug 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-353/egusphere-2024-353-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-353', Michael Fromm, 22 Mar 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-353/egusphere-2024-353-RC1-supplement.pdf
-
RC2: 'Comment on egusphere-2024-353', Anonymous Referee #3, 13 Jul 2024
This study uses satellite remote sensing datasets to examine the vertical extents of wildfire smoke, along with chemical signatures of biomass burning, during the record fire season of 2023 in Canada. This topic has high relevance for a broad community interested in the role of large wildfires in a warming climate system. However, several issues must be addressed prior to publication in ACP, which amount to a major revision.
While I understand the focus on stratospheric impacts (or the lack thereof), it would be nice to have a bit more focus on the potential implications of having so much smoke in the upper-troposphere. Can we say anything about what this might mean for future climate scenarios?
More information is needed in the methods section on how tropopause altitudes were calculated. This should be a stand-alone section. How do the methods used here to obtain tropopause altitude compare with previous studies that used other methods and data sources. There is currently only one sentence on using temperature profiles from ACE-FTS to derive tropopause altitude. How are these profiles derived? How does the accuracy compare with reanalysis or radiosonde temperature profiles? Have any previous studies used ACE-FTS to obtain tropopause altitudes?
Some of the figures in this paper present results with tropopause relative altitude while others use absolute altitude. It might be best to use one of these methods in all figures for consistency. In this case, tropopause relative altitude seems like the better choice?
The decision to omit MLS from the analysis in this paper needs more clarification. It seems that MLS and ACE-FTS have their own sets of strengths and weaknesses for a study like this. So, using them in combination would likely have benefits. MLS data have also been used in previous pyroCb plume studies. At minimum, the authors should cite some of this previous work as part of a more robust justification for why MLS is not used.
Fig. 1: Please provide more discussion on the tropopause altitude discrepancy in August. This relates to my tropopause methods comment above. Perhaps run some comparisons with tropopause altitudes derived from reanalysis data, such as MERRA-2. It may also be helpful to include a range or standard deviation marker for the tropopause, along with the mean.
It seems like the signal from the 2017 PNE is missing in the September panel (blue dashed curve)? I would expect to see a significant enhancement above the tropopause.
Fig 5: This might be more informative as an anomaly plot relative to the OMPS data record…or add a second panel with this anomaly information.
Fig. 6 and S4: The trajectory analysis can be improved. In Fig. 6, why was it decided to use multiple time intervals and constrain the trajectories to three days? The time of the ACE-FTS profile should be exact…there is no need for other times. This smoke could have originated from pyroCb activity more than three days before the ACE-FTS observations time. I recommend extending the duration of the trajectories to see if other fires in Canada might have contributed. For Fig. S4, the timing of the trajectories is also very questionable, when considering that a pyroCb event usually lasts for only a few hours. You can look at satellite imagery of the event to get a sense of how long it persisted, and thus the duration of the smoke injection window to launch trajectories from.
Fig. 7 legend: please make it clear which profile is 2023 vs. the 2017 PNE (red vs. black). That terminology is easier to digest than the profile numbers. Put the profile numbers in the caption.
Fig. 8 and S5: It took me a long time to digest what’s going on in these figures. The values of the mean curves in the time series are near the top of the color bar scale in the shaded plots when smoke is present, which doesn’t make sense. Are the curves the maximum value? In Fig. S5, the caption notes that different layers are used for these plots, but in Fig. 8 they use the same layer? Regardless, this analysis is critical to the narrative. It should all show in the main paper…not the supplement…after the errors are fixed.
Citation: https://doi.org/10.5194/egusphere-2024-353-RC2 -
RC3: 'Comment on egusphere-2024-353', Anonymous Referee #4, 26 Jul 2024
General comments:
The paper presents an interesting analysis on the presence of particles in the stratosphere from 2023 summer Canadian wildfires, using some satellite data. Nevertheless, the paper is too short, some works on the same subject need to be considered for an improved discussion, and perhaps others sources of data should be analyzed before concluding that such smoke particles from wildfire are rare in the stratosphere.
The paper need a major revised before it can be considered for publication.
Specific comments:
The authors speak of vertical extend, but no vertical profile of particles in the stratosphere are presented. So, the title of the paper must be changed, or real aerosol vertical data in the stratosphere, perhaps from different instrumental sources, must be considered.
Line 55 : Some publications are missing, in particular the ones showing that large amount of soot particles can be injected in the stratosphere during wildfire events. Also, others works are available on the vertical extend of smokes in the stratosphere. The authors must rewrite this paragraph, considering the recent results on the stratospheric solid particles and on vortex resulting from wildfires. Here some examples of papers:
- Sellitto, Pasquale & Belhadji, Redha & Cuesta, Juan & Podglajen, Aurélien & Legras, Bernard. (2023). Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating. 10.5194/egusphere-2023-1067.
- Lestrelin, Hugo & Legras, Bernard & Podglajen, Aurélien & Salihoglu, Mikail. (2021). Smoke-charged vortices in the stratosphere generated by wildfires and their behaviour in both hemispheres: comparing Australia 2020 to Canada 2017. Atmospheric Chemistry and Physics. 21. 7113-7134. 10.5194/acp-21-7113-2021.
- Renard, Jean-Baptiste, Berthet, Gwenaël, Levasseur-Regourd, Anny-Chantal , Beresnev, S. , Miffre, Alain , Rairoux, Patrick , Vignelles, Damien , Jegou, F.. (2020). Origins and Spatial Distribution of Non-Pure Sulfate Particles (NSPs) in the Stratosphere Detected by the Balloon-Borne Light Optical Aerosols Counter (LOAC). Atmosphere. 11. 10.3390/atmos11101031.
Can the authors provide error bars for the concentration in Figure 3 and Figure 4? Without such error bars, it is not possible to assess the reality of the detections.
Line 170-174 : This conclusion seems to be in contradiction with other works on this subject. The author must improve the bibliography and explain how their results can be compared to previous works and why they could differ.
Line 180: Figure 5 do not show the vertical profile of aerosol extinction, so how the authors can speak of a “significant decrease in signal past 11.5 km”?
Citation: https://doi.org/10.5194/egusphere-2024-353-RC3 -
AC1: 'Comment on egusphere-2024-353', Selena Zhang, 28 Aug 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-353/egusphere-2024-353-AC1-supplement.pdf
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Selena Zhang
Susan Solomon
Chris D. Boone
Ghassan Taha
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1655 KB) - Metadata XML
-
Supplement
(1119 KB) - BibTeX
- EndNote
- Final revised paper