Investigation of methane flux in South Asia using atmospheric measurements at Nainital, India and global Eulerian-Lagrangian coupled atmospheric model

Monday, 15 December 2014
Yukio Terao1, Misa Ishizawa1, Hitoshi Mukai1, Manish Kumar Naja2, Shohei Nomura1, Toshinobu Machida1, Ruslan Zhuravlev3,4, Alexander Ganshin3,4 and Shamil S Maksyutov1, (1)National Institute for Environmental Studies, Tsukuba, Japan, (2)Aryabhatta Research Institute of Observational-Sciences, Nainital, India, (3)Central Aerological Observatory, Moscow, Russia, (4)Tomsk State University, Tomsk, Russia
We have conducted air samplings at Nainital, India (29.36°N, 79.46°E, 1958 m a.s.l.) to analyze concentrations of greenhouse gases (CO2, CH4, N2O and SF6), CO, H2, and isotope ratios. The air samples were collected in 1.5 L Pyrex glass flasks at weekly time intervals. Here we discuss the methane flux in South Asia using Global Eulerian-Lagrangian Coupled Atmospheric (GELCA) model with the observational data of methane at Nainital.

The coupled model approach is suitable to represent observations at high spatial resolutions. The forward simulation represented a background feature of methane variations at Nainital, especially for low methane concentrations in winter. However, the simulation overestimated summer enhancement of methane concentrations. In summer, air parcels observed at Nainital were transported from Ganges basin thus the atmospheric observational data at Nainital might constrain the methane flux due to rice cultivations. The impact of Nainital data to the methane flux estimates is examined using an atmospheric inverse modeling system based on GELCA.