HR: 14:55h
AN: A23E-06    [Abstracts]
TI: The Stable Isotope Composition of Stratospheric and Mesospheric H$_{2}$
AU: * Rhee, T S
EM: rhee@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, 55020 Germany
AU: R\"{o}ckmann, T
AF: Max Planck Institute for Nuclear Physics, Atmospheric Physics Division, Heidelberg, 69029 Germany
AU: Brass, M
AF: Max Planck Institute for Nuclear Physics, Atmospheric Physics Division, Heidelberg, 69029 Germany
AU: Engel, A
AF: University of Frankfurt, Institute for Meteorology and Geophysics, Frankfurt, 60325 Germany
AU: Brenninkmeijer, C A
AF: Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, 55020 Germany
AB: Stratospheric H$_{2}$ is an intermediate in the chain of oxidation reactions of CH$_{4}$, which ends up with water vapor. Due to the similar reaction rates as CH$_{4}$, H$_{2}$ is in a photochemical steady state between production and destruction in view of mixing ratio. Its D/H ratio, however, is not at a steady state, but is enriched in deuterium associated with both the production and destruction reactions. In the upper stratosphere and mesosphere, water vapor is assumed to be a major source of H$_{2}$ by the photolytic reactions. We discuss the deuterium flow among the long-lived hydrogen compounds, CH$_{4}$, H$_{2}$, and H$_{2}$O in the stratosphere and mesosphere based on the recent observations of the mixing ratios and isotopic ratios of H$_{2}$ and CH$_{4}$ in the stratosphere. Air samples were collected by balloon flights in Aires sur l'Adour (France) in October, 2002, and in Kiruna (Sweden) in March and June, 2003. The D/H ratios of H$_{2}$ and CH$_{4}$ increase with altitude gradually, while the H$_{2}$ mixing ratios remain constant. Exception was observed in a winter flight in March. The H$_{2}$ mixing ratios were decreasing at ~18km but the isotopic ratios kept increasing. Above this layer H$_{2}$ rose to 840 ppb concomitant with a drop in the D/H ratio. We focus on this flight for discussion.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting