Atmospheric methane dynamics and its associations with environmental factors in the mid-Indo-Gangetic region (Bihar), India.

Atmospheric methane (CH4) is a potent greenhouse gas with a significantly higher global warming potential than carbon dioxide over a short-term period. In this study, we investigate the spatiotemporal variability of CH4 concentrations in the Bihar region, India, and assess the association of these concentrations with environmental factors such as meteorological conditions, vegetation indices, livestock population, and population density. Using high-resolution satellite data from the TROPOMI sensor (S5P), MODIS, and meteorological datasets, we analyze CH4 variations over a period from 2018 to 2023. A 2.8 % increase in XCH4 concentrations is observed over this period. Our findings reveal seasonal fluctuations in CH4 levels, with elevated concentrations during the monsoon and post-monsoon periods, attributed to flooding, agricultural practices, particularly rice cultivation, and wetland methanogenesis. Spatially, CH4 concentrations are highest in the mid-Gangetic plains, where average XCH4 concentration exceeds 1920 ppb. It attributes to anthropogenic activities, such as agriculture primarily rice and makhana cultivation, and livestock farming significantly contribute to emissions. Pearson correlation and regression analyses demonstrate a strong positive relationship between CH4 concentrations, vegetation indices (NDVI, EVI, and GPP), and relative humidity. Conversely, wind speed inversely correlates with CH4, influencing dispersion. The multiple regression model accounted for 43.4 % of the variance (p < 0.001) in XCH4 concentrations. The study also identifies CH4 hotspots and coldspots, with high emissions concentrated in flood-prone and agriculturally intensive areas. The identified hotspots exhibit an anomaly of about 12.5 ppb, indicating persistent local intensification of CH4 sources. Our research highlights the critical role of land-use patterns, climatic variability, and human activities in shaping CH4 dynamics in the region. These insights are vital for developing targeted mitigation strategies and informing state-level climate action policies to reduce CH4 emissions in Bihar.