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Temporal and latitudinal distributions of stratospheric N2O isotopomers
Department of Environmental Chemistry and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan
Solution Oriented Research for Science and Technology, Japan Science and Technology Corporation, Kawaguchi, Japan
Department of Environmental Chemistry and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan
Solution Oriented Research for Science and Technology, Japan Science and Technology Corporation, Kawaguchi, Japan
Frontier Collaborative Research Center, Tokyo Institute of Technology, Yokohama, Japan
Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
Department of Environmental Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
Department of Chemistry, Tokyo Institute of Technology, Tokyo, Japan
Department of Chemistry, Tokyo Institute of Technology, Tokyo, Japan
Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan
Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan
Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan
Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan
Division of Science Education, Miyagi University of Education, Sendai, Japan
National Institute for Environmental Studies, Tsukuba, Japan
National Institute for Polar Research, Tokyo, Japan
National Institute for Polar Research, Tokyo, Japan
Japan Space Exploration Agency, Sagamihara, Japan
Temporal and latitudinal variations of vertical profiles of N2O isotopomers were observed in the stratosphere over Japan (39°N, 142°E), Sweden (68°N, 20°E), and Antarctica (69°N, 40°E) during the period between 1990 and 2001. Samples were collected with a balloon-borne cryogenic sampler and analyzed by mass spectrometry in the laboratory. Observed enrichment factors for heavier isotopomers (15N14N16O, 14N15N16O, and 14N14N18O) relative to 14N14N16O were nearly constant in the lower stratosphere (less than ∼22 km) but increased at higher altitudes (∼22–35 km) while showing seasonal and latitudinal differences. Enrichment factors during the photolysis and photo-oxidation of N2O were also obtained in laboratory experiments and compared with those observed. We found that in the higher-altitude region (1) fractionation of the isotopomers is mainly determined by photolysis, but is also affected by physical processes, (2) subsidence of air masses in the winter polar vortex induces the intrusion of an upper stratospheric air mass depleted in N2O, and (3) decay of the vortex in the local spring leads to rapid horizontal advection of midlatitude air masses. At lower altitudes, isotopomer ratios are determined by photolysis, photo-oxidation, and the mixing of air masses within the stratosphere or between the stratosphere and the troposphere. Secular trend of isotopomer profiles was not detectable over Japan during 11 years. Assuming that the lower stratospheric air over midlatitudes is exchanged with the troposphere, isotopomer ratios of the N2O “back-flux” from the stratosphere were estimated. These values can be used in the isotopomeric mass balance model to constrain the global N2O budget.
Received 2 November 2003; accepted 11 March 2004; published 27 April 2004.
Citation: (2004), Temporal and latitudinal distributions of stratospheric N2O isotopomers, J. Geophys. Res., 109, D08308, doi:10.1029/2003JD004316.
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