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| − | == MEGAN prior to GEOS-Chem v8-02-04 ==
| + | This page describes the implementations of the MEGAN (Model of Emissions of Gases and Aerosols from Nature) biogenic emissions in GEOS-Chem. |
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| − | === MEGAN documentation ===
| + | == MEGAN 3.0 == |
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| − | '''''Dylan Millet (dbm@umn.edu) wrote:'''''
| + | An implementation of MEGAN 3.0 is currently a [https://github.com/geoschem/geos-chem/issues/1026 requested feature for GEOS-Chem development]. |
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| − | :There was discussion at the 2009 GC User's Meeting about divergent implementations of MEGAN and the need to better document what we're doing in GEOS-Chem. Here is a description (current as of 5/1/2009) for people to use and modify in their publications.
| + | == MEGAN v2.1 plus Guenther 2012 biogenic emissions == |
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| − | :We use the Model of Emissions of Gases and Aerosols from Nature (MEGAN) [Guenther et al., 2006] to derive isoprene emissions for each GEOS-Chem grid square [Palmer et al., 2006; Millet et al., 2008]. MEGAN computes emissions for plant functional types (PFTs) as a function of temperature, solar radiation, leaf area index (LAI), and leaf age. Fractional coverage for each PFT and vegetation-specific emission factors (EFs) are based on the MEGAN landcover data (PFT v2.0, EFs v2.0). The temperature effect on leaf emissions is computed as a function both of the current temperature and the average temperature over the previous 15 days [Guenther et al., 1999]. The implementation also includes a 5-layer canopy model [Guenther et al., 1999] to account for the effects of direct and diffuse PAR on sunlit and shaded leaves. We explicitly consider the effect of leaf age on emissions, with leaf age fractions for new, young, mature, and old leaves estimated for each model grid square from local LAI and temperature changes according to Guenther et al. [2006]. We drive MEGAN in GEOS-Chem with assimilated surface air temperature and photosynthetically active radiation (direct and diffuse) observations from the NASA Global Modeling and Assimilation Office (GMAO). Monthly mean LAI values are based on AVHRR satellite data [Buermann et al., 2002].
| + | GEOS-Chem currently uses the [[MEGAN v2.1 plus Guenther 2012 biogenic emissions|MEGAN 2.1 biogenic emissions with updates from Guenther (2012)]]. The emissions fed into GEOS-Chem by the [https://hemco.readthedocs.io Harmonized Emissions Component (HEMCO)] extension. |
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| − | :'''''References:
| + | --[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 21:10, 16 September 2022 (UTC) |
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| − | :#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'', <u>J. Geophys. Res.</u>, 107, 4646, doi:10.1029/2001JD000975, 2002.
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| − | :#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'', <u>J. Geophys. Res.</u>, 104, 30625-30639, 1999.
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| − | :#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)'', <u>Atmos. Chem. Phys.</u>, 6, 3181-3210, 2006.
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| − | :#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'', <u>J. Geophys. Res.</u>, 113, D02307, doi:10.1029/2007JD008950, 2008.
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| − | :#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'', <u>J. Geophys. Res.</u>, 111, D12315, doi:10.1029/2005JD006689, 2006.
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| − | --[[User:Dbm|Dbm]] 14:48, 1 May 2009 (EDT)
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| − | === Updated annual emission factor for Isoprene ===
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| − | In [[GEOS-Chem_versions_under_development#v7-04-12|GEOS-Chem v7-04-12]] (as of Sep 2007), we use the older annual emission factors (AEF's) for isoprene.
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| − | However, Alex Guenther (personal communication) uses the current isoprene AEF's were obsolete and that we should be using updated isoprene AEF's. Dylan Millet has created an updated AEF file for isoprene but it has not been implemented into the standard GEOS-Chem code yet. (Some folks have already used the new AEF's in their research codes.) The new AEF's are currently scheduled to be implemented in [[GEOS-Chem_versions_under_development#v8-01-02|GEOS-Chem beta release v8-01-02]].
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| − | '''Reference:''' Guenther, A., T. Karl, P. Harley, C. Wiedinmyer, P.I. Palmer, and C. Geron (2006), ''Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature)'', <u>Atmospheric Chemistry and Physics</u>, 6, 3181-3210.
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| − | '''MEGAN Website:''' [http://bai.acd.ucar.edu/Megan/index.shtml http://bai.acd.ucar.edu/Megan/index.shtml ]
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| − | --[[User:Bmy|Bob Y.]] 11:57, 2 December 2008 (EST) | + | |
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| − | === Impact on isoprene emissions ===
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| − | Here are some presentations which document the change in the MEGAN biogenic emissions of isoprene caused by switching to the new annual emission factor (AEF) file.
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| − | # [http://acmg.seas.harvard.edu/geos/wiki_docs/emissions/20070814_megan_comparison.pdf HERE] is a comparison (by Dylan Millet) of isoprene emissions from GEIA vs. old MEGAN (i.e. v8-01-03 and prior) vs. new MEGAN (v8-01-04 and later, with updated baseline annual emission factors from Alex Guenther). 2001, 2x2.5, v7-04-11, GEOS-4 met.
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| − | # [http://acmg.seas.harvard.edu/geos/wiki_docs/emissions/Benchmark_Comparison_MEGAN.pdf HERE] is a comparison (by Rynda Hudman) on the effects of MEGAN on the v7-02-04 benchmark.
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| − | '''''NOTE: The newer AEF's for isoprene are now used in [[GEOS-Chem versions under development#v8-01-04|GEOS-Chem v8-01-04]] and higher.'''''
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| − | --[[User:Bmy|Bob Y.]] 09:39, 3 March 2009 (EST)
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| − | == MEGAN in GEOS-Chem v8-02-04 and beyond ==
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This page describes the implementations of the MEGAN (Model of Emissions of Gases and Aerosols from Nature) biogenic emissions in GEOS-Chem.
