| Abstrakt: |
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] |
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