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.