the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 May 2026
Tracking organic compounds in smoke plumes using infrared satellite-based measurements
Abstract. We apply new measurements of methanol, ethene, ethyne, and HCN from the Cross-track Infrared Sounder (CrIS) to explore the quantitative use of satellite-based thermal infrared (IR) observations for fire studies. We focus analysis on the western U.S. during the 2018–2019 timeframes of two fire-focused aircraft campaigns, and use the GEOS-Chem model to guide interpretation. The CrIS data reveal large in-smoke enhancements and species:species correlations for targeted volatile organic compounds (VOCs), especially during the more active 2018 fire year. Spectral enhancements are strongest for methanol and ethene. For VOCs with similar vertical sensitivities the in-smoke correlations are height-independent and can be converted to column enhancement ratios without plume altitude information. For VOCs with dissimilar vertical sensitivities, spectral index correlations change coherently with altitude and may constrain injection or plume height changes. The mean (± σ) ethene:methanol ratio measured by CrIS across an ensemble of plumes (0.64 ± 0.24 mol/mol) matches bottom-up emission ratios (0.63 ± 0.08 mol/mol), but satellite-based and aircraft data both reveal greater variability than is predicted by GEOS-Chem. We propose that fire pyrolysis conditions are one driver of this variability and use in-situ data to show that near-field ethene:methanol ratios track pyrolysis conditions and hence inform the abundance of other emitted VOCs. Finally, we apply CrIS ethene:methanol ratios to estimate the high-temperature pyrolysis fraction for the same plume ensemble; the resulting fraction correlates with fire radiative power in a manner not well-captured by models.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
(5411 KB) - Metadata XML
-
Supplement
(3634 KB) - BibTeX
- EndNote
Status: open (until 05 Aug 2026)
- RC1: 'Comment on egusphere-2026-1669', Anonymous Referee #1, 08 Jul 2026 reply
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 337 | 55 | 18 | 410 | 33 | 19 | 21 |
- HTML: 337
- PDF: 55
- XML: 18
- Total: 410
- Supplement: 33
- BibTeX: 19
- EndNote: 21
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
This manuscript presents an analysis of several VOCs observed by the CrIS satellite instrument in wildfire plumes above North America during the summers of 2018 and 2019 (when the intensive campaigns WE-CAN and FIREX-AQ occurred).
More specifically, the authors use hyperspectral range index (HRI) observations of methanol, ethene, ethyne and HCN. To support interpretation, they use simulations performed using the GEOS-Chem chemistry-transport model including biomass burning emissions from the GFAS inventory, and radiative-transfer simulation with the LBLRTM model.
The authors aim at deriving information on emissions as a function of fire characteristics using enhancement VOC ratios, exploiting the different vertical sensitivities of the instrument to each compound.
The dependence of emission factors depending on the type of fuel burned and the burning efficiency is well established. While the type of fuel burned can be estimated using databases of land cover and vegetation, the fraction of a wildfire that is in flaming or smouldering phase is very difficult to estimate. Due to the lack of systematic constrain, emission inventories usually do not differentiate emission factors depending on the combustion phase, which leads to major uncertainties. The study presented here is therefore very interesting as it discusses the possibility to infer information of the pyrolysis conditions using VOC ratios observed from satellite in freshly emitted dense plumes. They show that observed ethene:methanol ratios can be linked to the fire radiative power (FRP).
The paper is well written and well structured. The figures and supplementary information clearly support the analysis. The large uncertainty and need for further investigation is also well discussed. For these reasons, I recommend publication with minor corrections.
Main comments.
I think that it would be important to better explain the methodology and uncertainties in the conversion from HRI enhancement ratios to molar ratios. From what I understand, the authors assume a linear dependence in order to avoid a full retrieval of VOC columns but it seems too simplified. What is the uncertainty of this method compared to the ratio of L2 columns?
The possible contribution of other sources to the observed HRI is not discussed. Does a seasonal average remove all possible contributions from biogenic sources? Could the model be used to check this assumption? The ΔHRI is sometimes negative in the maps…
Specific comments.
Section 2.1.
Section 2.3.
Section 3.1.
Section 3.3.
Section 3.4.