Atmospheric transport and chemistry of trace gases in LMDz5B: Evaluation and implications for inverse modelling

Research output: Contribution to journalArticle


Representation of atmospheric transport is a major source of error in the estimation of greenhouse gas sources and sinks by inverse modelling. Here we assess the impact on trace gas mole fractions of the new physical parameterizations recently implemented in the atmospheric global climate model LMDz to improve vertical diffusion, mesoscale mixing by thermal plumes in the planetary boundary layer (PBL), and deep convection in the troposphere. At the same time, the horizontal and vertical resolution of the model used in the inverse system has been increased. The aim of this paper is to evaluate the impact of these developments on the representation of trace gas transport and chemistry, and to anticipate the implications for inversions of greenhouse gas emissions using such an updated model. Comparison of a one-dimensional version of LMDz with large eddy simulations shows that the thermal scheme simulates shallow convective tracer transport in the PBL over land very efficiently, and much better than previous versions of the model. This result is confirmed in three-dimensional simulations, by a much improved reproduction of the radon-222 diurnal cycle. However, the enhanced dynamics of tracer concentrations induces a stronger sensitivity of the new LMDz configuration to external meteorological forcings. At larger scales, the inter-hemispheric exchange is slightly slower when using the new version of the model, bringing them closer to observations. The increase in the vertical resolution (from 19 to 39 layers) significantly improves the representation of stratosphere/troposphere exchange. Furthermore, changes in atmospheric thermodynamic variables, such as temperature, due to changes in the PBL mixing modify chemical reaction rates, which perturb chemical equilibriums of reactive trace gases.

One implication of LMDz model developments for future inversions of greenhouse gas emissions is the ability of the updated system to assimilate a larger amount of high-frequency data sampled at high-variability stations. Others implications are discussed at the end of the paper.


  • R. Locatelli
  • P. Bousquet
  • F. Hourdin
  • M. Saunois
  • A. Cozic
  • F. Couvreux
  • J. Y. Grandpeix
  • M. P. Lefebvre
  • C. Rio
  • P. Bergamaschi
  • S. D. Chambers
  • V. Kazan
  • S. Van Der Laan
  • H. A J Meijer
  • J. Moncrieff
  • M. Ramonet
  • H. A. Scheeren
  • C. Schlosser
  • M. Schmidt
  • A. G. Williams
External organisations
  • Laboratoire des Sciences du Climat et de l'Environnement
  • Laboratoire de Meteorologie Dynamique
  • Centre National de Recherches Météorologiques, Meteo-France
  • European Commission Joint Research Centre, Ispra
  • Australian Nuclear Science and Technology Organisation
  • Max Planck Institute for Biogeochemistry
  • University of East Anglia
  • University of Groningen
  • University of Edinburgh
  • Federal Office for Radiation Protection
  • Heidelberg University
  • Energy Research Centre of the Netherlands
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Earth and Related Environmental Sciences
Original languageEnglish
Pages (from-to)129-150
Number of pages22
JournalGeoscientific Model Development
Issue number2
Publication statusPublished - 2015 Feb 3
Publication categoryResearch
Externally publishedYes