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Accurate renditions of country-scale methane (CH 4 ) emissions are critical in understanding the regional CH 4 budget and essential for adapting national climate mitigation policies to curtail the atmospheric build-up of this greenhouse gas with high warming potential. India housing 30% of the Asian population is currently appraised as a region of CH 4 source based on the inventories. To date, there have not been many reported efforts to estimate the regional CH 4 emissions using direct measurements of boundary layer CH 4 concentrations at multiple locations over India. Here, 2 years (2017-2018) of in situ CH 4 observations from three distantly placed stations over the peninsular India is combined with state-of-the-art inversion using a Lagrangian particle dispersion model for the estimation of CH 4 emission. This study updates CH 4 emission over the peninsular India (land area south of 21.5°N) as ~ 10.63 Terra gram (Tg) CH 4 year -1 , which is 0.13 Tg CH 4 year -1 higher than the existing inventory-based emission. On seasonal scale, the changes from the existing CH 4 emission inventories are 0.12, 0.05, 0.055 and 0.28 Tg CH 4 year -1 during winter, pre-monsoon, monsoon and post-monsoon seasons respectively. Spatial distributions of seasonal variability of posterior emissions suggest an enhancement over the eastern region of peninsular India compared to the western part. The study with observations from three stations over the peninsular India provides an update on the inventory-based estimation of CH 4 emissions and urges the importance of more observations over the Indian region for the accurate estimation of fluxes., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Methane (CH4) is the second most abundant greenhouse gas and affects the Earth's radiative balance. In some regions, the methane burden and budget are still not well understood due to the lack of in situ observations, especially vertical profile observations. Here, we present the first high‐resolution aircraft‐based tropospheric vertical profiles of CH4 across the Indian subcontinent. Observations show significant variability, with the largest variability seen in the Indo‐Gangetic Plain (IGP) during post‐monsoon (September). The IGP also shows the highest concentrations and a peak in the boundary layer. By contrast, observations over western India show lower variability, especially during the Asian Summer Monsoon (ASM) (July). During ASM, when CH4 emissions peak, the vertical updraft of CH4 and other tracers is observed, leading to a peak between 4 and 5 km. During winter, the peak occurs in the boundary layer, and a decrease with altitude is observed. Model simulations slightly overestimate CH4 at the surface during some seasons but underestimate it at higher altitudes during all seasons. Integrated over the observed column, model simulations slightly underpredict CH4 (0.5%–3.1%) during all seasons. Calculations made using the observed CO/CH4 enhancement ratios show that in addition to anthropogenic fossil fuel emissions, other sources, such as rice cultivation and wetlands, need to be considered to reproduce the observed CH4 concentrations. Plain Language Summary: Methane is a potent greenhouse gas, which causes global warming. Aircraft‐based observations of methane were conducted over India to study the vertical variability. Observations show that methane is highly variable with altitude, and these vertical profiles are different according to the region and season in India. Models can reproduce the average vertical profiles but not individual flights. Using these data, estimations of methane emissions were also done, which show that current inventories need to account for all the different sources, including agriculture and wetlands. Key Points: First high‐resolution aircraft‐based tropospheric vertical profiles of methane over India are reportedObservations show a large variability of tropospheric methane across seasons and locationsModel simulations slightly underestimate the observed methane in the free troposphere [ABSTRACT FROM AUTHOR]