Graphical Abstract

Niwa, Y., K. Tsuboi, H. Matsueda, Y. Sawa, T. Machida, M. Nakamura, T. Kawasato, K. Saito, S. Takatsuji, K. Tsuji, H. Nishi, K. Dehara, Y. Baba, D. Kuboike, S. Iwatsubo, H. Ohmori, and Y. Hanamiya, 2014: Seasonal variations of CO₂, CH₄, N₂O and CO in the mid-troposphere over the western North Pacific observed using a C-130H cargo aircraft. J. Meteor. Soc. Japan, 92, 55–70.
https://doi.org/10.2151/jmsj.2014-104

Highlights:

Seasonal variations of carbon dioxide (CO₂), methane (CH₄), carbon monoxide (CO) and nitrous oxide (N₂O) in the mid-troposphere over the western North Pacific are investigated using air samples collected onboard a C-130H aircraft between Atsugi Base and Minamitorishima.
The C-130H aircraft observed high CH₄ concentration events in the mid-troposphere concomitantly with high CO concentrations, for both winter–spring and summer-fall. Average enhancement ratios of CH₄ to CO suggest that the high CH₄ concentrations originated primarily from fossil fuel combustions in winter–spring, while there could be an additional contribution from increased biogenic sources during summer–fall.
Because a surface station rarely observed the summer–fall high CH₄ concentration values in the mid-troposphere, the aircraft measurements could provide a powerful constraint on the CH₄ emission estimates for Asia, in addition to that provided by the surface measurements.