the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Leveraging TROPOMI observations and WRF-GHG modeling to improve methane emission assessments in India
Abstract. Atmospheric methane (CH4) contributes to global warming and climate change. Multiple factors control its atmospheric growth rate, posing challenges for climate change mitigation in regions with limited observations, like India. In this study, we examine the potential of dry air column methane mixing ratio (XCH4) observations from the TROPOspheric Monitoring Instrument (TROPOMI) in conjunction with the high-resolution Weather Research Forecast model with Greenhouse Gas module (WRF-GHG) to improve the annual CH4 budget of India. Our analysis demonstrates the potential of WRF-GHG to represent the atmospheric XCH4 and CH4 distributions, including seasonal patterns, albeit with non-negligible uncertainties when compared with satellite and ground-based observations for 2018 and 2019. We find that the WRF-GHG simulations overestimate the XCH4 and underestimate the near-surface CH4 distributions. Our first-order inversion analyses report annual CH4 emissions ranging from 23.3 to 25.2 Tg with an uncertainty of 3.3 Tg (anthropogenic sources), showing that the current global emission inventories overestimate CH4 emissions considerably. Our estimates are approximately 19 % higher than those in the India Fourth Biennial Update Report (19.6 Tg) and close to the latest Global Methane Budget 2000–2020 (21.7 Tg). Overall, this study demonstrates the usefulness of TROPOMI observations for assessing Indian CH4 emissions and shows a way to improve our understanding of how regional processes can modulate atmospheric CH4 mixing ratios. We highlight the need for expanded observational coverage and an improved carbon assimilation system over India to refine the methane budget in support of global climate goals.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-1977', Anonymous Referee #1, 30 Jun 2025
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RC2: 'Comment on egusphere-2025-1977', Anonymous Referee #2, 04 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1977/egusphere-2025-1977-RC2-supplement.pdf
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The manuscript presents an inversion of methane emissions over India using TROPOMI satellite observations in conjunction with the WRF-GHG model. Due to the lack of in situ measurements in India, the inversion relies entirely on TROPOMI observations.
India is a highly relevant methane emitter due to its large cattle population, rice cultivation, and fossil fuel use. Quantifying Indian CH₄ emissions and verifying reported or bottom-up estimated values is of great importance. Given the current scarcity of inverse studies focused on India, this regional inversion study has the potential to make a valuable contribution to the field.
The manuscript provides helpful background on Indian CH₄ emissions and their spatial, temporal, and sectoral characteristics. The simulation setup is described in a generally clear way and appears to be well-designed, with appropriate model resolution. The model has been evaluated against TROPOMI data and observations from the Thumba station. The results are broadly consistent with previous top-down estimates of Indian CH₄ emissions. However, I find that several aspects of the WRF-GHG model configuration and the inversion setup are insufficiently explained, and in some cases may require revision. In addition, the presented inversion results should be substantially expanded to fully support the study’s conclusions. Furthermore, I recommend a careful linguistic revision of the manuscript to improve clarity and readability.
General Comments
Technical Comments
Overall, this manuscript addresses a highly relevant topic and contributes important knowledge ond Indian CH4 emissions. However, several methodological clarifications and improvements to the result presentation are needed before the manuscript can be recommended for publication.