Articles | Volume 16, issue 22
Atmos. Chem. Phys., 16, 14169–14202, 2016
Atmos. Chem. Phys., 16, 14169–14202, 2016

Research article 16 Nov 2016

Research article | 16 Nov 2016

Global biogenic volatile organic compound emissions in the ORCHIDEE and MEGAN models and sensitivity to key parameters

Palmira Messina1, Juliette Lathière1, Katerina Sindelarova2,3, Nicolas Vuichard1, Claire Granier2,4,5,6, Josefine Ghattas7, Anne Cozic1, and Didier A. Hauglustaine1 Palmira Messina et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL, CEA/CNRS/OVSQ, Université Paris-Saclay, CEA-Orme des Merisiers, 91191 Gif-sur-Yvette, France
  • 2Laboratoire Atmosphères, Milieux, Observations Spatiales, LATMOS-IPSL, UPMC/CNRS/OVSQ, UPMC 4 Place Jussieu, 75252 Paris, France
  • 3Department of Atmospheric Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague, Czech Republic
  • 4Laboratoire d'Aérologie, CNRS-Université de Toulouse, Toulouse, France
  • 5Cooperative Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, Boulder, Colorado 80309, USA
  • 6National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway R/CSD, Boulder, Colorado 80305-3337, USA
  • 7Institut Pierre Simon Laplace des sciences de l'environnement, UPMC 4 Place Jussieu, 75252 Paris, France

Abstract. A new version of the biogenic volatile organic compounds (BVOCs) emission scheme has been developed in the global vegetation model ORCHIDEE (Organizing Carbon and Hydrology in Dynamic EcosystEm), which includes an extended list of biogenic emitted compounds, updated emission factors (EFs), a dependency on light for almost all compounds and a multi-layer radiation scheme. Over the 2000–2009 period, using this model, we estimate mean global emissions of 465 Tg C yr−1 for isoprene, 107.5 Tg C yr−1 for monoterpenes, 38 Tg C yr−1 for methanol, 25 Tg C yr−1 for acetone and 24 Tg C yr−1 for sesquiterpenes. The model results are compared to state-of-the-art emission budgets, showing that the ORCHIDEE emissions are within the range of published estimates. ORCHIDEE BVOC emissions are compared to the estimates of the Model of Emissions of Gases and Aerosols from Nature (MEGAN), which is largely used throughout the biogenic emissions and atmospheric chemistry community. Our results show that global emission budgets of the two models are, in general, in good agreement. ORCHIDEE emissions are 8 % higher for isoprene, 8 % lower for methanol, 17 % higher for acetone, 18 % higher for monoterpenes and 39 % higher for sesquiterpenes, compared to the MEGAN estimates. At the regional scale, the largest differences between ORCHIDEE and MEGAN are highlighted for isoprene in northern temperate regions, where ORCHIDEE emissions are higher by 21 Tg C yr−1, and for monoterpenes, where they are higher by 4.4 and 10.2 Tg C yr−1 in northern and southern tropical regions compared to MEGAN. The geographical differences between the two models are mainly associated with different EF and plant functional type (PFT) distributions, while differences in the seasonal cycle are mostly driven by differences in the leaf area index (LAI). Sensitivity tests are carried out for both models to explore the response to key variables or parameters such as LAI and light-dependent fraction (LDF). The ORCHIDEE and MEGAN emissions are differently affected by LAI changes, with a response highly depending on the compound considered. Scaling the LAI by a factor of 0.5 and 1.5 changes the isoprene global emission by −21 and +8 % for ORCHIDEE and −15 and +7 % for MEGAN, and affects the global emissions of monoterpenes by −43 and +40 % for ORCHIDEE and −11 and +3 % for MEGAN. Performing a further sensitivity test, forcing ORCHIDEE with the MODIS LAI, confirms the high sensitivity of the ORCHIDEE emission module to LAI variation. We find that MEGAN is more sensitive to variation in the LDF parameter than ORCHIDEE. Our results highlight the importance and the need to further explore the BVOC emission estimate variability and the potential for using models to investigate the estimated uncertainties.

Short summary
We provide BVOC emissions for the present scenario, employing the updated ORCHIDEE emission module and the MEGAN model. The modelling community still faces the problem of emission model evaluation because of the absence of adequate observations. The accurate analysis performed, employing the two models, allowed the various processes modelled to be investigated, in order to fully understand the origin of the mismatch between the model estimates and to quantify the emission uncertainties.
Final-revised paper