دورية أكاديمية
Vertical distributions of N2O isotopocules in the equatorial stratosphere
| العنوان: | Vertical distributions of N2O isotopocules in the equatorial stratosphere |
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| المؤلفون: | S. Toyoda, N. Yoshida, S. Morimoto, S. Aoki, T. Nakazawa, S. Sugawara, S. Ishidoya, M. Uematsu, Y. Inai, F. Hasebe, C. Ikeda, H. Honda, K. Ishijima |
| المصدر: | Atmospheric Chemistry and Physics, Vol 18, Pp 833-844 (2018) |
| بيانات النشر: | Copernicus Publications, 2018. |
| سنة النشر: | 2018 |
| المجموعة: | LCC:Physics LCC:Chemistry |
| مصطلحات موضوعية: | Physics, QC1-999, Chemistry, QD1-999 |
| الوصف: | Vertical profiles of nitrous oxide (N2O) and its isotopocules, isotopically substituted molecules, were obtained over the Equator at altitudes of 16–30 km. Whole air samples were collected using newly developed balloon-borne compact cryogenic samplers over the eastern equatorial Pacific in 2012 and Biak Island, Indonesia, in 2015. They were examined in the laboratory using gas chromatography and mass spectrometry. The mixing ratio and isotopocule ratios of N2O in the equatorial stratosphere showed a weaker vertical gradient than the previously reported profiles in the subtropical and mid-latitude and high-latitude stratosphere. From the relation between the mixing ratio and isotopocule ratios, further distinct characteristics were found over the Equator: (1) observed isotopocule fractionations (ε values) in the middle stratosphere (25–30 km or [N2O] −1) are almost equal to ε values reported from broadband photolysis experiments conducted in the laboratory; (2) ε values in the lower stratosphere (2O] > ca. 260 nmol mol−1) are about half of the experimentally obtained values, being slightly larger than those observed in the mid-latitude and high-latitude lower stratosphere ([N2O] > ca. 170 nmol mol−1). These results from the deep tropics suggest the following. (i) The timescale for quasi-horizontal mixing between tropical and mid-latitude air in the tropical middle stratosphere is sufficiently slow relative to the tropical upwelling rate that isotope fractionation approaches the Rayleigh limit for N2O photolysis. (ii) The air in the tropical lower stratosphere is exchanged with extratropical air on a timescale that is shorter than that of photochemical decomposition of N2O. Previously observed ε values, which are invariably smaller than those of photolysis, can be explained qualitatively using a three-dimensional chemical transport model and using a simple model that assumes mixing of aged tropical air and extratropical air during residual circulation. Results show that isotopocule ratios are useful to examine the stratospheric transport scheme deduced from tracer–tracer relations. |
| نوع الوثيقة: | article |
| وصف الملف: | electronic resource |
| اللغة: | English |
| تدمد: | 1680-7316 1680-7324 |
| Relation: | https://www.atmos-chem-phys.net/18/833/2018/acp-18-833-2018.pdf; https://doaj.org/toc/1680-7316; https://doaj.org/toc/1680-7324 |
| DOI: | 10.5194/acp-18-833-2018 |
| URL الوصول: | https://doaj.org/article/d8a55970317942758e53664a7b55ee6a |
| رقم الأكسشن: | edsdoj.8a55970317942758e53664a7b55ee6a |
| قاعدة البيانات: | Directory of Open Access Journals |
Full Text Finder | تدمد: | 16807316 16807324 |
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| DOI: | 10.5194/acp-18-833-2018 |