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@ARTICLE{Ehhalt:3197,
      author       = {Ehhalt, D.H. and Rohrer, F.},
      title        = {{T}he tropospheric cycle of {H}2: {A} critical review},
      journal      = {Tellus / B},
      volume       = {61},
      issn         = {0280-6509},
      address      = {Oxford [u.a.]},
      publisher    = {Wiley-Blackwell},
      reportid     = {PreJuSER-3197},
      pages        = {500 - 535},
      year         = {2009},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {The literature on the distribution, budget and isotope
                      content of molecular hydrogen (H2) in the troposphere is
                      critically reviewed. The global distribution of H2 is
                      reasonably well established and is relatively uniform. The
                      surface measurements exhibit a weak latitudinal gradient
                      with $3\%$ higher concentrations in the Southern Hemisphere
                      and seasonal variations that maximize in arctic latitudes
                      and the interior of continents with peak-to-peak amplitudes
                      up to $10\%.$ There is no evidence for a continuous
                      long-term trend, but older data suggest a reversal of the
                      interhemispheric gradient in the late 1970s, and an increase
                      in the deuterium content of H2 in the Northern Hemisphere
                      from 80 standard mean ocean water (SMOW) in the 1970s to 130
                      today. The current budget analyses can be divided in two
                      classes: bottom up, in which the source and sink terms are
                      estimated separately based on emission factors and turnovers
                      of precursors and on global integration of regional loss
                      rates, respectively. That category includes the analyses by
                      3-D models and furnishes tropospheric turnovers around 75 Tg
                      H2 yr−1. The other approach, referred to as top down,
                      relies on inverse modelling or analysis of the deuterium
                      budget of tropospheric H2. These provide a global turnover
                      of about 105 Tg H2 yr−1. The difference is due to a much
                      larger sink strength by soil uptake and a much larger H2
                      production from the photochemical oxidation of volatile
                      organic compounds (VOC) in the case of the top down
                      approaches. The balance of evidence seems to favour the
                      lower estimates—mainly due to the constraint placed by the
                      global CO budget on the H2 production from VOC. An update of
                      the major source and sink terms yields: fossil fuel use
                      11±4 TgH2 yr−1; biomass burning (including bio-fuel) 15
                      ± 6 Tg H2 yr−1; nitrogen fixation (ocean) 6 ± 3 Tg H2
                      yr−1; nitrogen fixation (land) 3 ± 2 Tg H2 yr−1;
                      photochemical production from CH4 23 ± 8 Tg H2 yr−1 and
                      photochemical production from other VOC 18 ± 7 Tg H2
                      yr−1. The loss through reaction of H2 with OH is 19 ± 5
                      Tg H2 yr−1, and soil uptake 60+30 −20 Tg H2 yr−1. All
                      these rates are well within the ranges of the corresponding
                      bottom up estimates in the literature. The total loss of 79
                      Tg H2 yr−1 combined with a tropospheric burden of 155 Tg
                      H2 yields a tropospheric H2 lifetime of 2 yr. Besides these
                      major sources of H2, there are a number of minor ones with
                      source strengths > 1 Tg H2 yr−1. Rough estimates for these
                      are also given.},
      cin          = {ICG-2},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB791},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK406},
      shelfmark    = {Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000266678200002},
      doi          = {10.1111/j.1600-0889.2009.00416.x},
      url          = {https://juser.fz-juelich.de/record/3197},
}