MEGAN v2.1 plus Guenther 2012 biogenic emissions

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On this page we describe the MEGAN v2.1 plus Guenther et al 2012 biogenic emissions, which are used in GEOS-Chem v10-01 and newer versions. The MEGAN emissions are fed into GEOS-Chem via the HEMCO emissions component.

Overview

Description

Dylan Millet wrote:

GEOS-Chem emission routines for biogenic VOCs have been updated to MEGAN2.1 as described in Guenther et al., Geosci. Model Dev., 5, 1471–1492, 2012. The net result is a 11-12% decrease in the global flux for isoprene, and a 30% increase in the global flux for total monoterpenes. Biogenic alkene emissions are now computed using MEGAN instead of by scaling to isoprene, as was done previously. Biogenic emissions of acetaldehyde are now included. Annual emission totals at 2x2.5 resolution for the different compounds are within ~20% of the values in Table 6 of Guenther et al., within the expected uncertainty associated with differing meteorology, years, etc. Note that global emissions can also change by 10% or more when running at 2x2.5 versus 4x5 degree horizontal resolution (for both the updated and the standard emission routines).
One of the ‘under-the-hood’ changes is that there is now a single driver routine for calculating MEGAN emissions across all compounds (GET_MEGAN_EMISSIONS). Previously we had separate driver routines for each individual compound. GET_MEGAN_EMISSIONS is passed the compound name, looks up or computes the appropriate parameters, and returns the corresponding emissions. This should hopefully make it much easier to add new compounds in the future, since one just has to add the appropriate parameter values for that compound. There are parameters included for a number of compounds not presently in the standard chemistry scheme - for use in specialized simulations and/or future inclusion in standard fullchem. Another under-the-hood change is that the PCEEA/PECCA flag is no longer needed since we use this scheme exclusively now.
The new MEGAN implementation computes emissions for certain compounds based on pre-defined emission factor maps provided with the MEGAN source code. For other compounds emissions are computed in GEOS-Chem based on CLM4 plant functional type distributions combined with PFT-specific emission factors. This PFT approach can be used for all MEGAN compounds if desired (by adding in the corresponding emission factors for each PFT), which may be useful for applications using different vegetation maps or dynamically shifting vegetation.
The updated emissions lead to lower CO concentrations in the Northern Hemisphere during summer. A v9-1-3 4x5 run for 2006 gave CO mixing ratios averaged for P>800 hPa) that were lower by a few ppb over much of the Northern Hemisphere during ummer months. Maximum decreases of about 10ppb occur over certain source regions. Ox changes are small (< 2ppb for P > 800hPa) using the standard v9-1-3 (non-Caltech) chemistry scheme.

Please contact Dylan Millet with any further questions about these emissions.

--Bob Y. 16:05, 25 February 2015 (EST)

Documentation

  • Comparison between previous and updated BVOC emissions for standard tracers (year-2006):
  • Comparison between previous and updated BVOC emissions for standard tracers (nested NA, year-2011):
  • Updated emissions for all BVOCs, including non-standard tracers:
  • Monthly CO comparison for previous and updated MEGAN implementation (year-2006; 4x5 resolution):

--Dbm 14:18, 22 January 2013 (EST)

Data files

In GEOS-Chem v10-01 and newer versions, the MEGAN v2.1 plus Guenther (2012) biogenic emissions are read with the HEMCO emissions component. We have created new MEGAN data files (in COARDS-compliant netCDF format) for use with HEMCO. These new data files are contained in the HEMCO data directory tree. For detailed instructions on how to download these data files to your disk server, please see our Downloading the HEMCO data directories wiki post.

--Bob Y. 16:02, 25 February 2015 (EST)

CO2 direct effect on isoprene emissions

This update is slated for inclusion in GEOS-Chem v10-01 or later

Amos Tai developed code updates to include CO2 inhibition of isoprene emissions in MEGAN.

The reference for this work is:

Tai, A.P.K., L.J. Mickley, C.L. Heald, S. Wu, Effect of CO2 inhibition on biogenic isoprene emission: Implications for air quality under 2000-to-2050 changes in climate, vegetation, and land use, Geophys. Res. Let., 40, 3479-3483, 2013. [pdf]

--Melissa Sulprizio 15:45, 23 January 2014 (EST)

References

  1. Barkley, M., Description of MEGAN biogenic VOC emissions in GEOS-Chem, 2010. PDF
  2. Buermann, W., Wang, Y.J., Dong, J.R., Zhou, L.M., Zeng, X.B., Dickinson, R.E., Potter, C.S., and Myneni, R.B.: Analysis of a multiyear global vegetation leaf area index data set, J. Geophys. Res., 107, 4646, doi:10.1029/2001JD000975, 2002.
  3. Guenther, A., Baugh, B., Brasseur, G., Greenberg, J., Harley, P., Klinger, L., Serca, D., and Vierling, L.: Isoprene emission estimates and uncertainties for the Central African EXPRESSO study domain, J. Geophys. Res., 104, 30625-30639, 1999.
  4. Guenther, A., Karl, T., Harley, P., Wiedinmyer, C., Palmer, P.I., and Geron, C.: Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature), Atmos. Chem. Phys., 6, 3181-3210, 2006.
  5. Guenther, A., and C. Wiedinmyer, User's guide to the Model of Emissions of Gases and Aerosols from Nature (MEGAN), Version 2.01, 2007.
  6. Guenther, A. B., Jiang, X., Heald, C. L., Sakulyanontvittaya, T., Duhl, T., Emmons, L. K., and Wang, X.: The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions, Geosci. Model Dev., 5, 1471-1492, doi:10.5194/gmd-5-1471-2012, 2012. Article
  7. Millet, D.B., Jacob, D.J., Boersma, K.F., Fu, T.M., Kurosu, T.P., Chance, K., Heald, C.L., and Guenther, A.: Spatial distribution of isoprene emissions from North America derived from formaldehyde column measurements by the OMI satellite sensor, J. Geophys. Res., 113, D02307, doi:10.1029/2007JD008950, 2008. PDF
  8. Mueller, J.-F., et al. Global isoprene emissions estimated using MEGAN, ECMWF analyses and a detailed canopy environment model, Atmos. Chem. Phys., 8, 1329-1341, 2008.
  9. Myneni, R. B., et al., Large seasonal swings in leaf area of Amazon rainforests, Proceedings of the National Academy of Sciences, 104(12), 4820{4823, doi:10.1073/pnas.0611338104, 2007.
  10. Palmer, P.I., Abbot, D.S., Fu, T.M., Jacob, D.J., Chance, K., Kurosu, T.P., Guenther, A., Wiedinmyer, C., Stanton, J.C., Pilling, M.J., Pressley, S.N., Lamb, B., and Sumner, A.L.: Quantifying the seasonal and interannual variability of North American isoprene emissions using satellite observations of the formaldehyde column, J. Geophys. Res., 111, D12315, doi:10.1029/2005JD006689, 2006. PDF
  11. Sakulyanontvittaya, T., T. Duhl, C. Wiedinmyer, D. Helmig, S. Matsunaga, M. Potosnak, J. Milford, and A. Guenther, Monoterpene and Sesquiterpene Emission Estimates for the United States, Environ. Sci. Technol., 42(5), 1623{1629, doi:10.1021/es702274e, 2008.

--Bob Y. 15:49, 25 February 2015 (EST)

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