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Media type:
E-Article
Title:
Global budget of molecular hydrogen and its deuterium content: Constraints from ground station, cruise, and aircraft observations
Contributor:
Price, Heather;
Jaeglé, Lyatt;
Rice, Andrew;
Quay, Paul;
Novelli, Paul C.;
Gammon, Richard
imprint:
American Geophysical Union (AGU), 2007
Published in:Journal of Geophysical Research: Atmospheres
Language:
English
DOI:
10.1029/2006jd008152
ISSN:
0148-0227
Origination:
Footnote:
Description:
<jats:p>The distribution and atmospheric budgets for molecular hydrogen and its deuterium component <jats:italic>δ</jats:italic>D are simulated with the GEOS‐Chem global chemical transport model and constrained by observations of H<jats:sub>2</jats:sub> from the NOAA Climate Monitoring and Diagnostics Laboratory network and <jats:italic>δ</jats:italic>D observations from ship and ground stations. Our simulation includes a primary H<jats:sub>2</jats:sub> source of 38.8 Tg a<jats:sup>−1</jats:sup> (22.7 Tg a<jats:sup>−1</jats:sup> from fossil and biofuels, 10.1 Tg a<jats:sup>−1</jats:sup> from biomass burning, 6.0 Tg a<jats:sup>−1</jats:sup> from the ocean) (where a is years) and a secondary photochemical source from photolysis of formaldehyde of 34.3 Tg a<jats:sup>−1</jats:sup>. The simulated global tropospheric mean H<jats:sub>2</jats:sub> is 525 ppbv, with a tropospheric burden of 141 Tg and tropospheric lifetime of 1.9 a. Uptake by enzymes in soils accounts for 75% of the H<jats:sub>2</jats:sub> sink, with the remainder due to reaction with OH. The model captures the observed latitudinal, vertical, and seasonal variations of H<jats:sub>2</jats:sub>. For <jats:italic>δ</jats:italic>D we find that a photochemical source signature from methane and biogenic volatile organic compound oxidation of 162‰ yields a global mean atmospheric <jats:italic>δ</jats:italic>D of 130‰, consistent with atmospheric observations. The model captures the observed latitudinal gradient in <jats:italic>δ</jats:italic>D, simulating a 21‰ greater enrichment in the Southern Hemisphere because of the predominance of isotopically depleted fossil fuel emissions in the Northern Hemisphere. We find that stratospheric‐tropospheric exchange results in 37‰ enrichment of tropospheric <jats:italic>δ</jats:italic>D. Our simulation provides new simultaneous constraints on the H<jats:sub>2</jats:sub> soil sink (55 ± 8 Tg a<jats:sup>−1</jats:sup>), the ocean source (6 ± 3 Tg a<jats:sup>−1</jats:sup>), and the isotopic signature for photochemical production (162 ± 57‰).</jats:p>