HR: 1330h
AN: A52A-0770    [PDF]
TI: Modeling the Extreme Deuterium Enrichment in Stratospheric Hydrogen
AU: * McCarthy, M C
EM: mike_mac@uclink4.berkeley.edu
AF: Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720 United States
AU: Connell, P
EM: connell2@llnl.gov
AF: Atmospheric Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 United States
AU: Boering, K A
EM: boering@cchem.berkeley.edu
AF: Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720 United States
AU: Boering, K A
EM: boering@cchem.berkeley.edu
AF: Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, CA 94720 United States
AB: Observations of the isotopic composition of molecular hydrogen in whole air samples collected by the NASA ER-2 aircraft showed extreme enrichment in deuterium of up to 440 per mil on the V-SMOW isotope scale [Rahn et al., Nature, 2003]. In this study, we use the Lawrence Livermore National Laboratory 2D model to investigate the extreme deuterium enrichment in stratospheric H$_{2}$ and find that kinetic isotope effects (KIEs) in the oxidation of H$_{2}$ in the stratosphere account for over 60% of the enrichment while production of heavy H$_{2}$ from CH$_{4}$ oxidation accounts for the remainder. The sensitivity of the H$_{2}$ isotopic composition to uncertainties in the CH$_{4}$ oxidation pathway branching ratios, formaldehyde oxidation KIEs, formaldehyde photolysis isotope effects, and the H$_{2}$ oxidation KIEs is explored, and recommendations for needed laboratory and field measurements based on these model sensitivities are given. Finally, we investigate the global H$_{2}$ isotope budget using model estimates of $\delta$D-H$_{2}$ produced from CH$_{4}$ oxidation in both the stratosphere and troposphere.
DE: 0322 Constituent sources and sinks
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting