CH4 simulation

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This page contains information about the methane (CH4) simulation in GEOS-Chem.


Authors and collaborators

Previous authors include:

  • Kevin Wecht (formerly @ Harvard)
  • Christopher Pickett-Heaps (formerly @ Harvard)
  • Jerome Drevet (formerly @ EPFL)
  • James Wang (formerly @ Harvard)

CH4 simulation user groups

See this post on the Carbon Cycle Working Group wiki page.

Recent science updates

The following updates were recently added into the GEOS-Chem CH4 simulation:

Updated CH4 simulation in v11-02 and later

This update was included in v11-02f (approved 17 May 2018).

Bram Maasakkers and Melissa Sulprizio have updated the CH4 simulation in GEOS-Chem v11-02. These updates include the following emission updates (brought in via HEMCO):

  1. EDGAR v4.3.2 global anthropogenic emissions
  2. Gridded US EPA emissions (Maasakkers et al. 2016)
  3. Canada and Mexico oil & gas emissions (Sheng et al. 2017)
  4. Daily QFED biomass burning emissions
  5. JPL WetCHARTs emissions (Bloom et al. 2017)
  6. Global geological seep emissions (Maasakkers et al., in prep)
  7. Global lake emissions (Maasakkers et al., in prep)

and code updates:

  1. CH4 loss by Cl (Maasakkers et al., in prep)
  2. GOSAT and TCCON observation operators (modified from the adjoint code)

The following data files are required for these updates  (entire directory)

A few caveats:

  • EDGAR v4.3.2 lumps oil, gas, and coal emissions in the files available on their website. Ideally, we would like to separate these sources, so we are looking into that. In addition, Tia Scarpelli at Harvard is developing a global oil and gas CH4 emissions inventory which will be included in the future. Until we resolve this, the EDGAR v4.3.2 lumped oil/gas/coal emissions are added to CH4_OIL in the tagged CH4 simulation and CH4_GAS, CH4_COL only include emissions from Canada, US, and Mexico.
  • EDGAR v4.3.2 rice emissions by default are annual emissions. For our CH4 simulations, we generated monthly EDGAR rice emissions by applying seasonality from the Zhang et al. (2016). We had to preprocess the EDGAR files to do this and haven't yet figured out a way to apply the seasonality via HEMCO -- it may require writing an extension. If you're interested in using our EDGAR seasonal rice emissions, please let us know and we can send you those files.
  • We have updated rice emissions from Zhang et al. (2016), but we don't have permission to share those data yet. We used those rice emissions in Maasakkers et al. (in prep) to apply seasonality to the EDGAR v4.3.2 rice emissions.
  • We recommend not use the lakes emissions (they are turned off by default in HEMCO_Config.rc). There is some concern it leads to double-counting when used together with WetCHARTS. It’s something we’ll look into but just using WetCHARTS for now is a cleaner approach.
  • There’s a small issue with incorporating offshore GEPA emissions right now (as those fall outside of the US mask. We’re working on resolving that.

--Bob Yantosca (talk) 16:00, 17 May 2018 (UTC)

Update CH4 emissions to EDGAR v4.2

The CH4 simulation now uses emissions from the EDGAR v4.2 inventory.

In GEOS-Chem v10-01 and newer versions

In GEOS-Chem v10-01 and newer versions, EDGAR v4.2 CH4 emissions are read with the HEMCO emissions component. We have created new emission data files for the CH4 simulation (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. 13:23, 3 March 2015 (EST)

In GEOS-Chem versions prior to v10-01

This update was tested in the 1-month benchmark simulation v9-02m and approved on 30 Jul 2013. This update is included in Adjoint v35d.

Kevin Wecht has prepared EDGAR v4.2 emissions of methane for 2004-2008. The data files are available at:

You can download these directories with anonymous FTP or the Wget utility. For instructions, please see Chapter 2.4, Downloading the GEOS-Chem shared data directories in the GEOS-Chem Online User's Guide.

Modifications to subroutines RICE_EMIS and ASEASONAL_ANTHRO_EMIS in global_ch4_mod.F include changing the directory names and updating CYEAR and XTAU as follows:

     WRITE( CYEAR, '(i4)' ) GET_YEAR()
     XTAU = GET_TAU0( 1, 1, GET_YEAR() )

     IF ( GET_YEAR() .LT. 2004 )  THEN
        XTAU = GET_TAU0( 1, 1, 2004 )
     IF ( GET_YEAR() .GT. 2008 ) THEN
        XTAU = GET_TAU0( 1, 1, 2008 )

--Melissa Payer 16:53, 2 July 2013 (EDT)



  1. Bloom, A. A., Bowman, K. W., Lee, M., Turner, A. J., Schroeder, R., Worden, J. R., Weidner, R., McDonald, K. C., and Jacob, D. J.: A global wetland methane emissions and uncertainty dataset for atmospheric chemical transport models (WetCHARTs version 1.0), Geosci. Model Dev., 10, 2141-2156,, 2017.
  2. Sheng, J.-X., D. J. Jacob, J.D. Maasakkers, M.P. Sulprizio, D. Zavala-Areiza, and S. Hamburg, A high-resolution (0.1ox0.1o) inventory of methane emissions from Canadian and Mexican oil and gas systems, Atmos. Environ., 158, 211-215, 2017. [PDF]
  3. Maasakkers, J.D., D.J.Jacob, M.P. Sulprizio, A.J. Turner, M. Weitz, T. Wirth, C. Hight, M. DeFigueiredo, M. Desai, R. Schmeltz, L. Hockstad, A.A. Bloom, K.W. Bowman, S. Jeong, and M.L. Fischer, Gridded national inventory of U.S. methane emissions, Environ. Sci. Technol., 50, 13123−13133, 2016. [PDF]
  4. Turner, A. J., Jacob, D. J., Wecht, K. J., Maasakkers, J. D., Biraud, S. C., Boesch, H., Bowman, K. W., Deutscher, N. M., Dubey, M. K., Griffith, D. W. T., Hase, F., Kuze, A., Notholt, J., Ohyama, H., Parker, R., Payne, V. H., Sussmann, R., Velazco, V. A., Warneke, T., Wennberg, P. O., and Wunch, D.: Estimating global and North American methane emissions with high spatial resolution using GOSAT satellite data, Atmos. Chem. Phys. Discuss., 15, 4495-4536, doi:10.5194/acpd-15-4495-2015, 2015.
  5. Turner, A. J. and Jacob, D. J.: Balancing aggregation and smoothing errors in inverse models, Atmos. Chem. Phys. Discuss., 15, 1001-1026, doi:10.5194/acpd-15-1001-2015, 2015.
  6. Wecht, K.J., D.J. Jacob, C. Frankenberg, Z. Jiang, and D.R. Blake, Mapping of North America methane emissions with high spatial resolution by inversion of SCIAMACHY satellite data, submitted to J. Geophys. Res., 2014.
  7. Wecht, K.J., D.J. Jacob, M.P. Sulprizio, G.W. Santoni, S.C. Wofsy, R. Parker, H. Bösch, and J.R. Worden, Spatially resolving methane emissions in California: constraints from the CalNex aircraft campaign and from present (GOSAT, TES) and future (TROPOMI, geostationary) satellite observations, Atm. Chem. Phys. Discuss., 14, 4119-4198, doi:10.5194/acpd-14-4119-2014, 2014.
  8. Wecht, K.J., D.J. Jacob, S.C. Wofsy, E.A. Kort, J.R. Worden, S.S. Kulawik, D.K. Henze, M. Kopacz, and V.H. Payne, Validation of TES methane with HIPPO aircraft observations: implications for inverse modeling of methane sources, Atmos. Chem. Phys., 12, 1823-1832, 2012.
  9. Pickett-Heaps, C.A., D.J. Jacob, K.J. Wecht, E.A. Kort, S.C. Wofsy, G.S. Diskin, D.E.J. Worthy, J.O. Kaplan, I. Bey, and J. Drevet, Magnitude of seasonality of wetland methane emissions from the Hudson Bay Lowlands (Canada), Atmos. Chem. Phys., 11(8), 3773-3779, doi:10.5194/acp-11-3773-2011, 2011.
  10. Wang, J.S., J.A. Logan, M.B. McElroy, B.N. Duncan, I.A. Megretskaia, and R.M. Yantosca, A 3-D model analysis of the slowdown and interannual variability in the methane growth rate from 1988 to 1997, Global Biogeochem. Cycles, 18, GB3011, doi:10.1029/2003GB002180, 2004.

Previous issues that are now resolved

The following bugs and/or issues with the code have now been resolved:

Add fixes for seasonal scale factors in CH4 simulations

These updates were included in GEOS-Chem 12.1.0, which was released on 26 Nov 2018.

Seasonal manure emissions

The seasonal scale factor files for rice and manure CH4 emissions are available for 2009-2015. The CH4 simulation will crash with a HEMCO error when running outside of that time range because HEMCO can't find a file for that year. To fix this, Bram Maasakkers has generated climatology scale factors for years outside that range. A new file has been created and the climatology values have been added to years 2008 and 2016. That way, with the "C" cycling flag set the climatology scaling factors will be used outside of 2009-2015. The new file also combines the yearly files into a single file without $YYYY in the filename.

# Old entry in HEMCO_Config.rc:
10 MANURE_SF $ROOT/CH4/v2017-10/Seasonal_SF/EMICH4_Manure_ScalingFactors_$            sf_ch4 $YYYY/1-12/1/0     C xy 1 1

# New entry in HEMCO_Config.rc:
10 MANURE_SF $ROOT/CH4/v2017-10/Seasonal_SF/  sf_ch4 2008-2016/1-12/1/0 C xy 1 1

--Melissa Sulprizio (talk) 19:31, 7 November 2018 (UTC)

Seasonal rice emissions

Hannah Nesser noted considerable differences in rice emissions totals between 4x5 and 2x2.5 methane simulations. The issue was traced to the use of zero values in the rice scaling factors file, which caused issues when regridding the 0.1x0.1 degree scale factors to 4x5 and 2x2.5 resolution. To resolve the issue, a new file was created in which zero values are replaced with missing values.

# Old entry in HEMCO_Config.rc:
11 RICE_SF   $ROOT/CH4/v2017-10/Seasonal_SF/             sf_ch4 2012/1-12/1/0  C xy 1 1

# New entry in HEMCO_Config.rc:
11 RICE_SF   $ROOT/CH4/v2017-10/Seasonal_SF/  sf_ch4 2012/1-12/1/0  C xy 1 1

--Melissa Sulprizio (talk) 19:31, 7 November 2018 (UTC)

Now call INIT_GLOBAL_CH4 from input_mod.F

This update was validated in the 1-month benchmark simulation v10-01c and approved on 29 May 2014.

Prior to GEOS-Chem v10-01, routine INIT_GLOBAL_CH4 (in module GeosCore/global_ch4_mod.F) was called from the main driver routine main.F at the start of the simulation.

In order to make the code more compatible with our Grid-Independent GEOS-Chem development, we now call INIT_TAGGED_CH4 from routine GIGC_INIT_EXTRA (in module GeosCore/input_mod.F).

--Bob Y. 16:59, 30 May 2014 (EDT)

Minor fixes to CH4 simulation for MERRA meteorology

These updates were validated in the 1-month benchmark simulation v10-01c and approved on 29 May 2014.

We have made a couple of fixes to the CH4 simulation module (GeosCore/global_ch4_mod.F) for compatibility with the MERRA met fields. At lines 1114, and again at line 1503, there were #if blocks that looked like this:

#if   defined( GEOS_5 ) || defined( GEOS_FP )

but these should have been:

#if   defined( GEOS_5 ) || defined( GEOS_FP ) || defined( MERRA )

Furthermore, in data directory GEOS_4x5/CH4_201305/wetlands, we have symbolically linked files:

GWETTOP.geos5.4x5.YYYY.bpch --> GWETTOP.merra.4x5.YYYY.bpch
TSKIN.geos5.4x5.YYYY.bpch   --> TSKIN.merra.4x5.YYYY.bpch

where YYYY = { 2004, 2005, 2006, 2007, 2008, 2009, 2010 }.

These issues were discovered with the GEOS-Chem Unit Tester.

--Bob Y. 16:59, 30 May 2014 (EDT)

Unresolved issues

Obsolete information

These sections pertain to code that has been removed from the most recent versions of GEOS-Chem. We shall leave this information here for reference.

Update methane emissions and add capability for North America nested grid


In GEOS-Chem v10-01 and newer versions, CH4 emissions are implemented via the HEMCO emissions component.

This update was tested in the 1-month benchmark simulation v9-01-03h and approved on 09 Mar 2012.

Kevin Wecht wrote:

I have some GEOS-Chem methane updates that I'd like to add to the standard code.
  1. GFED emissions - I've updated GFED-2 and GFED-3 biomass burning to include methane emissions.
  2. Methane simulation - I've updated emissions and error catches to make the simulation compatible with the nested simulation over North America. I added linearized CH4 chemistry from GMI output (CH4 loss frequencies generated by Lee Murray). These changes should be made to the data directory:
a. Replace Carbon_soil, Carbon_litter, and Wetfrac files in data directory (for all horizontal resolutions)
b. Add 2010-2011 TSKIN and GWETTOP files to data directory (for all horizontal resolutions)
c. Add nested north american OH files to OH directory
d. Add biofuel emissions to data directory (for all horizontal resolutions)
e. Add all emission files to data directory for nested North America simulation

The error in reading GWETTOP fields is also fixed in this update.

--Melissa Payer 17:35, 2 February 2012 (EST)

Notes about the methane simulation


In GEOS-Chem v10-01 and newer versions, CH4 emissions are implemented via the HEMCO emissions component.

1. The methane simulation uses monthly and annual average skin temperature and soil moisture values from the met fields. These are calculated offline using IDL (""). This file can be found on the ftp site in the methane data directory with the LPJ wetland emission scheme (e.g., "GEOS_0.5x0.666_NA/CH4_201305/wetlands"). The script should work as is for 2004-2011, however we don't currently have the met data for 2012 so you may need to modify "global_ch4_mod.F" if you're interested in 2012 or 2013.
Subroutine "WETLAND_EMIS"
        YEAR = GET_YEAR()
        #if   defined( GEOS_5 )
        IF ( YEAR .LT. 2004 ) YEAR  = 2004
        IF ( YEAR .GT. 2011 ) YEAR  = 2011
Subroutine "RICE_EMIS"
        ! Get annual and monthly mean soil wetness from GEOS
        ! One file contains both monthly and annual mean GWETTOP
        YEAR = GET_YEAR()
        #if   defined( GEOS_5 )
        IF ( YEAR .LT. 2004 ) YEAR  = 2004
        IF ( YEAR .GT. 2011 ) YEAR  = 2011
2. Seasonality of Rice Emissions: Seasonality in the rice emissions is imposed through annual and monthly average soil moisture values. This works reasonably well for major rice growing areas like South/East Asia where rice paddies are rain-fed, but it fails in other regions. For example, California rice paddies are irrigated and crops are grown in the summer, precisely when the natural soil is the driest. You can enter the "global_ch4_mod.F", subroutine "RICE_EMIS", and impose any seasonality you want on the annual emission rates from EDGAR.
3. Potential Global Mean Bias: The methane simulation may not simulate global average concentrations accurately. That is, you may have a mean bias of up to +/-30ppbv when you compare the simulation to observations. A global mean bias means that the model has a slight imbalance between the sources and sinks relative to the world. You may want to consider removing this mean bias before analyzing your model concentrations.

--Alex Turner 11:01, 24 January 2014 (EST)

Fixes for wetland emissions


In GEOS-Chem v10-01 and newer versions, CH4 emissions are implemented via the HEMCO emissions component.

These issues were resolved during the public comment period following the provisional release of GEOS-Chem v9-02 and were included in the official release of GEOS-Chem v9-02 (03 Mar 2014). This update is included in Adjoint v35j.

Kevin Wecht wrote:

I have some updates/bug fixes to wetland emissions in the methane simulation. Both changes impact global_ch4_mod.F, subroutine WETLAND_EMIS.
1. Christopher Pickett-Heaps added a feature that zeroes wetland emissions if snow covers the ground. This was never incorporated into the standard code. It is included in the attached file.
2. Parameters in the subroutine are not correct. The following values are the correct and are included in the attached file:
          MOIST_SCALE = 0.205
          EMIT_FACT   = 0.018

--Melissa Sulprizio 16:11, 23 January 2014 (EST)
--Bob Y. 10:25, 4 April 2014 (EDT)

Error reading GWETTOP fields


In GEOS-Chem v10-01 and newer versions, CH4 emissions are implemented via the HEMCO emissions component.

This update was tested in the 1-month benchmark simulation v9-01-03h and approved on 09 Mar 2012.

There is a file read error in the current CH4 simulation. We will fix this issue in GEOS-Chem v9-01-03.

In RICE_EMIS (global_ch4_mod.F), XTAU is reset to the wrong value when GEWTTOP is read. Kevin Wecht provided a fix that accounts for different availabilities of GEOS-4 and GEOS-5 met fields. Prior to setting FILENAME for GWETTOP , add the following:

      YEAR = GET_YEAR()
#if   defined( GEOS_5 )
      IF ( YEAR .LT. 2004 ) YEAR  = 2004
      IF ( YEAR .GT. 2009 ) YEAR  = 2009
#elif defined( GEOS_4 )
      IF ( YEAR .LT. 2000 ) YEAR  = 2000
      IF ( YEAR .GT. 2006 ) YEAR  = 2006
      WRITE( CYEAR, '(i4)' ) YEAR
Also change:
     XTAU = GET_TAU0( 1, 1, GET_YEAR() )
     XTAU = GET_TAU0( GET_MONTH(), 1, GET_YEAR() )
     XTAU = GET_TAU0( 1, 1, YEAR )
     XTAU = GET_TAU0( GET_MONTH(), 1, YEAR )

--Melissa Payer 18:06, 2 February 2012 (EST)