the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Jul 2025
Stratospheric impact of the anomalous 2023 Canadian wildfires: the two vertical pathways of smoke
Abstract. The climate-altering potential of wildfires through their emissions into the stratosphere has only recently been realized following the major wildfire outbreaks in Canada and Australia. The 2023 Canadian wildfire season stood out for its extended burned area and duration, by far exceeded the previous record-breaking events, including the Australian “Black Summer” in terms of the emitted power and pyroCb count with a total number of 142 Canadian pyroCb events over the season. The incessant fire activity all across Canada produced a succession of smoke injections into the lower stratosphere. Here, we use various satellite data sets, airborne and ground-based observations together with chemistry-transport model simulations to show that despite the exceptional vigor of the 2023 Canadian wildfires, the depth of their stratospheric impact was surprisingly shallow and limited to the lowermost stratosphere. Conversely, the incessant fire activity featuring a long succession of moderate-strength pyroCb events, combined with numerous episodes of synoptic-scale smoke uplift through the warm conveyor belt, led to unparalleled levels of pollution at commercial aircraft cruising altitudes throughout the season.
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RC1: 'Comment on egusphere-2025-3152', Anonymous Referee #1, 08 Jul 2025
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Review of “Stratospheric impact of the anomalous 2023 Canadian wildfires: the two vertical pathways of smoke” by Khaykin et al.
The manuscript focuses on the extreme wildfire season in 2023 in Canada. It is highlighted that smoke is able to reach the upper troposphere and lower stratosphere in the absence of pyroCb convection if it is injected into a warm conveyor belt. This result is interesting and promising, however, a few general and technical comments follow here:
General comments:
Line 100: Maybe it would be good to change the order of 2.4 TROPOMI and 2.5 OMPS Limb Profiler in order to have OMPS Nadir Mapper and OMPS Limb Profiler in a row.
Line 135: How do you justify the thresholds: “0.01 for SAOD and 8 for ER”
Line 238: North America or Canada?
Line 252: Is the threshold of AAI > 15 arbitrarily chosen?
Table 1: WCB used as acronym but only defined in line 391
Fig. 1: Why starting at different years 2003, 2013, 2012 for A, B, C and not in the same year for all?
Fig. 4: legend caption: kg m³ there is a minus missing before the “3”
Fig. 4 and lines 457-463: The events 3, 4, 5, 6 all bring parts of the smoke into the lower stratosphere. You write that the lofting of smoke is meteorologically driven in the WCB and that the diabatic lofting plays a minor role. I understand that vertical transport of smoke in the WCB towards the tropopause is predominantly meteorologically driven. But how can you be sure that the smoke transport through the barrier of the tropopause would happen if it is only meteorologically driven? How would this barrier be passed even in a WCB? How can you exclude that at this point diabatic lofting might dominate to come across the barrier as diabatic lofting plays a big role in the stratosphere? And could differences in the absorptivity of the smoke compared to the Australian wildfire smoke in 2020 explain differences in diabatic lofting behavior? Please discuss this in your manuscript in more detail. Another question that just comes to my mind: Did you also find smoke transport towards the UTLS (within the tropopshere) if the smoke was not within a WCB (or pyroCb) before?
Line 688-690: Too general. In France? Or at that station? Or for Canadian smoke? How can you be sure it was a new record? At least the Australian 2020 smoke had a higher AOD for single layers in the stratosphere.
General: Maybe it would be a good idea to include a schematic figure comparing pyroCb and WCB vertical pathways, showing uplift speed, plume structure, and evolution over time.
General: It is good to see that the model could show the lofting of the aerosol in the WCB. It is good to see that the lidar profile shows an AOT of around 1 with a thick smoke plume in the stratosphere. But do you have any case where you also see the observational evidence that the smoke plume does not originate from a pyroCb but was injected at around 2km height in Canada and was later found at a significantly higher altitude? The manuscript would benefit from it.
Technical comments:
Line 37: Empty space missing after „precipitation”
Line 39: Bracket opened but not closed
Line 56: Which year of the study Peterson et al. ? (“n.d.”)
Line 60: Bracket opened but not closed
Line 62: Commas around “however” missing
Line 62: Brackets around Zhang et al need to be removed
Line 78: Brackets around Fromm et al need to be removed
Line 106: Empty space before “OMPS” missing
Line 109: Point missing at the end of the sentence
Line 134: Bracket opened but not closed
Line 168: remove brackets around Guth et al…
Line 184: remove brackets around El Amraoui et al., 2022; Sič et al., 2015
Line 197: remove brackets around (Nédélec et al., 2015)
Line 198: remove brackets around (Blot et al., 2021)
Line 220: remove brackets around Khaykin et al., 2017
Line 392: lofting air instead of lifting
Line 436: these instead of this
Line 505: remove brackets once around Yu et al.
Line 576: 23 UTC, not 23 h UTC
Citation: https://doi.org/10.5194/egusphere-2025-3152-RC1
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