Articles | Volume 14, issue 12
Atmos. Chem. Phys., 14, 6177–6194, 2014
Atmos. Chem. Phys., 14, 6177–6194, 2014

Research article 23 Jun 2014

Research article | 23 Jun 2014

TransCom N2O model inter-comparison – Part 2: Atmospheric inversion estimates of N2O emissions

R. L. Thompson2,1, K. Ishijima3, E. Saikawa5,4, M. Corazza6, U. Karstens7, P. K. Patra3, P. Bergamaschi6, F. Chevallier2, E. Dlugokencky8, R. G. Prinn4, R. F. Weiss9, S. O'Doherty10, P. J. Fraser11, L. P. Steele11, P. B. Krummel11, A. Vermeulen12, Y. Tohjima13, A. Jordan7, L. Haszpra14,15, M. Steinbacher16, S. Van der Laan20,*, T. Aalto18, F. Meinhardt19, M. E. Popa7,17, J. Moncrieff21, and P. Bousquet2 R. L. Thompson et al.
  • 1Norwegian Institute for Air Research, Kjeller, Norway
  • 2Laboratoire des Sciences du Climat et l'Environnement, Gif sur Yvette, France
  • 3Research Institute for Global Change, JAMSTEC, Yokohama, Japan
  • 4Center for Global Change Science, MIT, Cambridge, MA, USA
  • 5Emory University, Atlanta, GA, USA
  • 6Institute for Environment and Sustainability, JRC, Ispra, Italy
  • 7Max Planck Institute for Biogeochemistry, Jena, Germany
  • 8NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, CO, USA
  • 9Scripps Institution of Oceanography, La Jolla, CA, USA
  • 10Atmospheric Chemistry Research Group, School of Chemistry, University of Bristol, Bristol, UK
  • 11Centre for Australian Weather and Climate Research, CSIRO, Marine and Atmospheric Research, Aspendale, Victoria, Australia
  • 12Energy Research Centre of the Netherlands (ECN), Petten, the Netherlands
  • 13National Institute for Environmental Studies, Tsukuba, Japan
  • 14Hungarian Meteorological Service, Budapest, Hungary
  • 15Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Sopron, Hungary
  • 16Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, Switzerland
  • 17Institute for Marine and Atmospheric Research Utrecht, University of Utrecht, Utrecht, the Netherlands
  • 18Finnish Meteorological Institute, Helsinki, Finland
  • 19Umweltbundesamt, Messstelle Schauinsland, Kirchzarten, Germany
  • 20Centre for Isotope Research, University of Groningen, Groningen, the Netherlands
  • 21School of GeoSciences, The University of Edinburgh, Edinburgh, UK
  • *now at: School of Environmental Sciences, University of East Anglia, Norwich, UK

Abstract. This study examines N2O emission estimates from five different atmospheric inversion frameworks based on chemistry transport models (CTMs). The five frameworks differ in the choice of CTM, meteorological data, prior uncertainties and inversion method but use the same prior emissions and observation data set. The posterior modelled atmospheric N2O mole fractions are compared to observations to assess the performance of the inversions and to help diagnose problems in the modelled transport. Additionally, the mean emissions for 2006 to 2008 are compared in terms of the spatial distribution and seasonality. Overall, there is a good agreement among the inversions for the mean global total emission, which ranges from 16.1 to 18.7 TgN yr−1 and is consistent with previous estimates. Ocean emissions represent between 31 and 38% of the global total compared to widely varying previous estimates of 24 to 38%. Emissions from the northern mid- to high latitudes are likely to be more important, with a consistent shift in emissions from the tropics and subtropics to the mid- to high latitudes in the Northern Hemisphere; the emission ratio for 0–30° N to 30–90° N ranges from 1.5 to 1.9 compared with 2.9 to 3.0 in previous estimates. The largest discrepancies across inversions are seen for the regions of South and East Asia and for tropical and South America owing to the poor observational constraint for these areas and to considerable differences in the modelled transport, especially inter-hemispheric exchange rates and tropical convective mixing. Estimates of the seasonal cycle in N2O emissions are also sensitive to errors in modelled stratosphere-to-troposphere transport in the tropics and southern extratropics. Overall, the results show a convergence in the global and regional emissions compared to previous independent studies.

Final-revised paper