the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Aug 2026
Quantifying methane emissions by combining multi-instrument airborne observations with regional atmospheric transport modelling: application to Madrid waste sites
Abstract. Regulating the emission of methane (CH4) from anthropogenic sources plays an important role in global climate mitigation strategies. The waste sector is responsible for some of the strongest localized sources and therefore its control has the potential for high impact reduction measures.
As shown in a related preceding publication, airborne lidar and imaging spectrometer data provide reliable measurements of CH4 columns and can be used to estimate CH4 fluxes from sources such as landfills. However, incomplete knowledge of the transport of greenhouse gases from the source to the measurement point is one of the main sources of uncertainty in flux determination.
In this paper, we improve the accuracy over previous emission estimates by applying a new analysis method, based on high-resolution regional-scale weather simulations to describe the atmospheric transport. We use this model to perform a combined fit to the CH4 measurements from airborne lidar and passive remote sensing, as well as in situ measurements. The key improvement over previous estimates comes from explicitly accounting for the complex, time-varying wind field on the measurement day, which caused significant CH4 accumulation that biased earlier cross-sectional flux estimates.
This investigation focuses on two waste facilities close to Madrid, Spain, which were overflown by the German research aircraft HALO during a flight of the CoMet 2.0 Arctic mission. The estimated emission rates for the two sites were determined to be 4.0 ± 1.2 t h-1 (Pinto landfill) and 4.7 ± 0.7 t h-1 (Valdemingómez waste site).
Competing interests: At least one of the (co-)authors serves as editor for the special issue to which this paper belongs.
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
(1856 KB) - Metadata XML
- BibTeX
- EndNote
Status: open (until 22 Oct 2026)
- RC1: 'Comment on egusphere-2026-4578', Anonymous Referee #1, 25 Sep 2026 reply
-
RC2: 'Comment on egusphere-2026-4578', Anonymous Referee #2, 09 Oct 2026
reply
This paper re-analyses an already published dataset with a refined wind field modeling. They update the estimations of methane releases from two landfills near Madrid, Spain, to slightly lower numbers.
The article is overall very clear and documented, and the results well explained. I recommend the publication with minor, even optional comments.
l. 68 to 74: emission estimates at these 2 landfills from satellite missions are available from CarbonMapper (https://data.carbonmapper.org/?details=CH4_6A_1000m_-3.58861_40.32117%3Fstatus%3Dnot_deleted&plume_id=tan20260818t123448c13s4001-A#13.52/40.3313/-3.56365) and IMEO (https://methanedata.unep.org/map?fs=mars&e=y8a58pvMwzoVYEiNusf4Yg#mcoord=11.52/40.3394/-3.5771) data providers.
l. 220: I suggest moving or copying this description in the legend of Figure 2.
Citation: https://doi.org/10.5194/egusphere-2026-4578-RC2 -
RC3: 'Comment on egusphere-2026-4578', Anonymous Referee #3, 13 Oct 2026
reply
General assessment
This manuscript addresses a scientifically relevant topic: the quantification of anthropogenic methane (CH₄) emissions from waste management facilities. The study revisits airborne measurements collected over the Pinto landfill and the Valdemingómez waste site on 4 August 2022, combining three complementary measurement techniques with high-resolution WRF-GHG modelling and a χ²-based inversion framework.
The estimated emission rates are 4.0 ± 1.2 t h⁻¹ for Pinto and 4.7 ± 0.7 t h⁻¹ for Valdemingómez. The main contribution is the explicit representation of time-varying atmospheric transport, including wind rotation and methane accumulation, which can affect conventional cross-sectional flux estimates.
The manuscript is clearly written, well organised and scientifically relevant. I recommend publication subject to clarification of the following points.
Main comments
1. Interpretation of the claimed improvement in emission accuracy
The authors claim that the proposed method provides more accurate estimates than the conventional cross-sectional approach. Although modelling the time-varying wind field provides a physically sound explanation for the differences observed, the spread across five planetary boundary layer (PBL) schemes characterises model sensitivity rather than independently establishing absolute accuracy. The authors should distinguish more clearly between improved representation of atmospheric transport and demonstrated accuracy of the resulting emission estimates.
2. Temporal representativeness and implications of the emission estimates
The revised estimates improve upon those reported by Krautwurst et al. (2025) by accounting for the complex atmospheric transport conditions during the measurement flight. However, the results are based on a single measurement episode and therefore provide limited information on the temporal variability and longer-term emission rates of the two waste sites. The authors should clarify to what extent these estimates improve the understanding of the facilities' overall emissions, and acknowledge that repeated measurements under different conditions would be needed to assess their temporal representativeness.
Citation: https://doi.org/10.5194/egusphere-2026-4578-RC3
Video supplement
WRF-simulated CH4 plume evolution over Madrid waste sites for five PBL schemes, 4 August 2022 Fruck and Wolff https://doi.org/10.5281/zenodo.21068389
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 220 | 124 | 48 | 392 | 51 | 49 |
- HTML: 220
- PDF: 124
- XML: 48
- Total: 392
- BibTeX: 51
- EndNote: 49
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Please find my review attached.