% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@BOOK{Basu:137092,
      author       = {Basu, Abhijit},
      title        = {{A}n analysis of the global atmospheric methane budget
                      under different climates},
      volume       = {168},
      school       = {Universität Köln},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2013-03568},
      isbn         = {978-3-89336-859-4},
      series       = {Schriftenreihe des Forschungszentrums Jülich Reihe Energie
                      $\&$ Umwelt, Energy $\&$ Environment},
      pages        = {111 p.},
      year         = {2013},
      note         = {Universität Köln, Diss., 2013},
      abstract     = {Methane is the second most important gas after CO$_{2}$ in
                      the atmosphere in terms of radiative forcing. It also plays
                      an important role in tropospheric chemistry and influences
                      the oxidation capacity of atmosphere and amount of CO,
                      O$_{3}$ and water vapour. Various biogenic and anthropogenic
                      sectors including gas and oil extraction, wetlands, animal
                      ruminants emit methane in the atmosphere while it is mainly
                      OH which displaces it. At present, the mean global methane
                      concentration is balanced approximately at 1780 ppb after
                      undergoing several changes over the past decades. The
                      sources and sinks currently contribute between 450 and 510
                      Tg per year although the strength of each source components
                      suffers from uncertainty. Methane is also assumed to be a
                      key player in past climatic changes and its global abundance
                      underwent several transitions which were recorded in the ice
                      cores. One of the drastic changes in methane mixing ratio is
                      observed during the last glacial-interglacial transition, as
                      it shows an increasing trend from 350 ppb till it reaches
                      700 ppb at the pre-industrial Holocene. The post industrial
                      increase in global methane concentration is also
                      unprecedented. In this study, methane distribution at
                      present climate as well as at Last Glacial Maximum (LGM) and
                      pre-industrial era is simulated with a simplified global
                      tropospheric model ECHAM MOZ. For this simulation, methane
                      emissions from various inventories have been used. A new
                      parameterisation method is developed to estimate wetland
                      methane emission for present day which is later adapted for
                      LGM and pre-industrial time. Wetlands are the largest
                      natural source of methane, still suffers from huge
                      uncertainties. Contrary to the other hydrological models,
                      the present wetland parameterisation follows a simplified
                      approach based on a handful of soilparameters from CARAIB
                      vegetation model. This method is easily adaptable to past
                      climate simulations. The model result for present day from
                      ECHAM MOZ chemistry simulation has been validated with
                      station observation data across the globe and a set of
                      sensitivity analysis with the modified sources are carried
                      out to optimize the global methane budget. One of the major
                      findings from this study is the optimized wetland methane
                      strength which falls in the lower range of IPCC AR4 report.
                      The ECHAM MOZ transient simulation could produce the recent
                      methane trend and inter annual variability between 1990 and
                      2006 reasonably well although shows an underestimation in a
                      range of 20-40 ppb for the first eight years. This is
                      perhaps caused due to the underestimation of the oil and gas
                      extracted methane source used in the model. For LGM and
                      pre-industrial period, the model, using my wetland methane
                      source successfully reproduces the ice core methane records.
                      Compared to previous studies, the present LGM model source
                      strengthis weaker which raises the possibility of a less
                      deviated sink than present. This is supported by some recent
                      studies on the tropospheric oxidative chemistry which found
                      less OH variability than previously assumed. The important
                      aspect of the present study is that contrary to previous
                      studies where sinks are often hold responsible to explain
                      atmospheric methane variability, here the emphasis has been
                      given to the role of changing source based on these recent
                      findings.},
      keywords     = {Dissertation (GND)},
      cin          = {IEK-8},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {233 - Trace gas and aerosol processes in the troposphere
                      (POF2-233)},
      pid          = {G:(DE-HGF)POF2-233},
      typ          = {PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/137092},
}