Vertical profile of the carbon isotopic ratio of stratospheric methane over Japan

S. Sugawara, T. Nakazawa, Y. Shirakawa, K. Kawamura, S. Aoki, T. Machida, H. Honda

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39 Citations (Scopus)


Stratospheric air samples were collected over Japan on August 31, 1994 using a balloon-borne cryogenic sampler and then analyzed for the CH4 concentration and δ13C in CH4. The δ13C value increased from about -47.5 %̊ at the tropopause to about -38.9 %̊ at 34.7 km, accompanied by a rapid decrease of the CH4 concentration with height. From the measured values of the CH4 concentration and δ13C, the apparent carbon isotopic fractionation factor was estimated to be 1.0131±0.0006. The contributions of the chemical CH4 reactions with OH, O(1D) and Cl were also examined by using an one-dimensional photochemical-diffusion model. It is suggested from this examination that the reaction of CH4 with Cl is especially important for δ13C in the stratosphere.

Original languageEnglish
Article number97GL03044
Pages (from-to)2989-2992
Number of pages4
JournalGeophysical Research Letters
Issue number23
Publication statusPublished - 1997

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)


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