the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Aug 2025
Comment on “Thermal infrared observations of a western United States biomass burning aerosol plume” by Sorenson et al. (2024)
Abstract. Sorenson et al. (2024) studied fresh smoke plumes from the proximal Dixie fire in northern California and concluded that the smoke cooled the air and Earth surface below the smoke by shielding of incoming solar radiation. The so-attributed cooling was immediate, sudden and on par with diurnal temperature variations. This comment takes issue with their conclusions, reasoning, and method. By examining the same case and others, it is shown that the observed cooling within the smoke plume is caused by plume particulates sufficiently large to intercept and thereby alter upwelling thermal infrared radiation. The evidence presented is the same satellite and radar data employed by Sorenson et al., but expanded with temporal animations. A key element of the new analysis is the demonstration of smoke-associated cooling at nighttime, a circumstance decoupled from the solar-shielding explanation. The refutation of the proposed solar-shield-cooling in fresh smokes is an essential refinement of the constraints on the radiative cause-effect in such conditions.
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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
(866 KB)
- Corresponding article
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Supplement
(85272 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.
- Preprint
(866 KB) - Metadata XML
- Corresponding article
-
Supplement
(85272 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-2932', Sophie Vandenbussche, 22 Aug 2025
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AC1: 'Reply on RC1', Michael Fromm, 26 Sep 2025
I appreciate that the reviewer found the Comment compelling. Each and every minor/technical suggestion is understood and will be addressed in the revised manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-2932-AC1
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AC1: 'Reply on RC1', Michael Fromm, 26 Sep 2025
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RC2: 'Comment on egusphere-2025-2932', Anonymous Referee #1, 29 Aug 2025
I recommend this Comment be accepted as is. I'm in full agreement with the points made by the author regarding Sorensen (2024).
Citation: https://doi.org/10.5194/egusphere-2025-2932-RC2 -
AC2: 'Reply on RC2', Michael Fromm, 26 Sep 2025
It is gratifying to receive this blanket endorsement of my Comment. I thank the reviewer for the feedback.
Citation: https://doi.org/10.5194/egusphere-2025-2932-AC2
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AC2: 'Reply on RC2', Michael Fromm, 26 Sep 2025
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EC1: 'Comment on egusphere-2025-2932', Stelios Kazadzis, 31 Oct 2025
Dear authors
Here is a comment on the paper by Sorenson et al.
Due to technical issues I had to upload it myself.
best regards
SK-
AC3: 'Reply on EC1', Michael Fromm, 24 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2932/egusphere-2025-2932-AC3-supplement.pdf
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AC3: 'Reply on EC1', Michael Fromm, 24 Nov 2025
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-2932', Sophie Vandenbussche, 22 Aug 2025
This work provides a second analysis of the Dixie fires impact on thermal IR radiance. It refutes some of the argumentation of the initial paper (S24), provides additional analysis and data, and a different conclusion.
Being a reviewer of the initial S24 paper, I remained unconvinced by the plausibility of a BT drop as large as 25K only due to insulation reduction. Although this specific point was never fully addressed, all data and explanations were scientifically reasonable as far as I am able to judge. In particular, the absence of night-time TIR signal is crucial in justifying the explanation of insulation reduction.
The work from M. Fromm presented here provides very relevant additional data in the analysis, from different times and/or instruments and some data aggregated in useful movies. In particular, it shows a clear and significant TIR night-time signature of the plume, and a different radar analysis including discussion of the important limitations of such observations, which were not discussed in S24 and are beyond my scientific expertise. These represent convincing evidence towards the presence of particles causing TIR extinction, adding to the insulation shielding and providing a reasonable explanation for a satellite BT drop as high as 25K.
I think that this work bring significant additional scientific elements as much as the initial S24 paper, and must be published. Hopefully this will foster scientific discussions to disentangle the TIR impact of fire plumes, which is of very high importance for their detection, observation and modelling. To my point of view, even after both analyses of the Dixie fires, some observations remain not fully explained, such as a different VIS / SWIR / TIR relationship at different moments of the event. Hopefully both these publications will foster additional research in this field.
I have only a small amount of minor comments / corrections on this manuscript:
Lines 61-63: please also mention the effect of the surface emissivity - if it is much lower than 1 then the satellite BT also significantly diverges from the surface skin T
Line 84: I think the word "sufficed" comes out too strong, as S24 did not only rely on the absence of SWIR signal to get to their conclusions
Line 100: typo in DIxie
Line 237: I think there is one "at" too many
Figures 1 and 2: I can't read the scale / legend
Figure 4: I think the caption should contain all relevant information (except if very long) so I would avoid sending back to the text for the coordinates; also I would specify 2m air temperature (if I am correct) and 10.3µm window BT (again if correct)
Citation: https://doi.org/10.5194/egusphere-2025-2932-RC1 -
AC1: 'Reply on RC1', Michael Fromm, 26 Sep 2025
I appreciate that the reviewer found the Comment compelling. Each and every minor/technical suggestion is understood and will be addressed in the revised manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-2932-AC1
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AC1: 'Reply on RC1', Michael Fromm, 26 Sep 2025
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RC2: 'Comment on egusphere-2025-2932', Anonymous Referee #1, 29 Aug 2025
I recommend this Comment be accepted as is. I'm in full agreement with the points made by the author regarding Sorensen (2024).
Citation: https://doi.org/10.5194/egusphere-2025-2932-RC2 -
AC2: 'Reply on RC2', Michael Fromm, 26 Sep 2025
It is gratifying to receive this blanket endorsement of my Comment. I thank the reviewer for the feedback.
Citation: https://doi.org/10.5194/egusphere-2025-2932-AC2
-
AC2: 'Reply on RC2', Michael Fromm, 26 Sep 2025
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EC1: 'Comment on egusphere-2025-2932', Stelios Kazadzis, 31 Oct 2025
Dear authors
Here is a comment on the paper by Sorenson et al.
Due to technical issues I had to upload it myself.
best regards
SK-
AC3: 'Reply on EC1', Michael Fromm, 24 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2932/egusphere-2025-2932-AC3-supplement.pdf
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AC3: 'Reply on EC1', Michael Fromm, 24 Nov 2025
Peer review completion
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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.
- Preprint
(866 KB) - Metadata XML
This work provides a second analysis of the Dixie fires impact on thermal IR radiance. It refutes some of the argumentation of the initial paper (S24), provides additional analysis and data, and a different conclusion.
Being a reviewer of the initial S24 paper, I remained unconvinced by the plausibility of a BT drop as large as 25K only due to insulation reduction. Although this specific point was never fully addressed, all data and explanations were scientifically reasonable as far as I am able to judge. In particular, the absence of night-time TIR signal is crucial in justifying the explanation of insulation reduction.
The work from M. Fromm presented here provides very relevant additional data in the analysis, from different times and/or instruments and some data aggregated in useful movies. In particular, it shows a clear and significant TIR night-time signature of the plume, and a different radar analysis including discussion of the important limitations of such observations, which were not discussed in S24 and are beyond my scientific expertise. These represent convincing evidence towards the presence of particles causing TIR extinction, adding to the insulation shielding and providing a reasonable explanation for a satellite BT drop as high as 25K.
I think that this work bring significant additional scientific elements as much as the initial S24 paper, and must be published. Hopefully this will foster scientific discussions to disentangle the TIR impact of fire plumes, which is of very high importance for their detection, observation and modelling. To my point of view, even after both analyses of the Dixie fires, some observations remain not fully explained, such as a different VIS / SWIR / TIR relationship at different moments of the event. Hopefully both these publications will foster additional research in this field.
I have only a small amount of minor comments / corrections on this manuscript:
Lines 61-63: please also mention the effect of the surface emissivity - if it is much lower than 1 then the satellite BT also significantly diverges from the surface skin T
Line 84: I think the word "sufficed" comes out too strong, as S24 did not only rely on the absence of SWIR signal to get to their conclusions
Line 100: typo in DIxie
Line 237: I think there is one "at" too many
Figures 1 and 2: I can't read the scale / legend
Figure 4: I think the caption should contain all relevant information (except if very long) so I would avoid sending back to the text for the coordinates; also I would specify 2m air temperature (if I am correct) and 10.3µm window BT (again if correct)