CH4 simulation

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

Overview

The CH4 simulation in GEOS-Chem ...

Authors and collaborators

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

CH4 simulation user groups

User Group	Personnel	Projects
Harvard University	Christopher Pickett-Heaps Kevin Wecht	Methane sources in the Arctic
U. Wollongong	Chris Chan Miller	Methane sources in tropical Australia

Planned updates

Update methane emissions and add capability for North America nested grid

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)

Update CH4 emissions to EDGAR v4.2

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

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

ftp://ftp.as.harvard.edu/pub/geos-chem/data/GEOS_0.5x0.666_NA/CH4_201305/

ftp://ftp.as.harvard.edu/pub/geos-chem/data/GEOS_2x2.5/CH4_201305/

ftp://ftp.as.harvard.edu/pub/geos-chem/data/GEOS_4x5/CH4_201305/

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
        CYEAR='2004'
        XTAU = GET_TAU0( 1, 1, 2004 )
     ENDIF
     IF ( GET_YEAR() .GT. 2008 ) THEN
        CYEAR='2008'
        XTAU = GET_TAU0( 1, 1, 2008 )
     ENDIF

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

Fixes for wetland emissions

These issues were resolved during the public comment period following the provisional release of GEOS-Chem v9-02 and will be included in the official release of GEOS-Chem v9-02.

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)

Previous issues that are now resolved

Error reading GWETTOP fields

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
#endif
      WRITE( CYEAR, '(i4)' ) YEAR

Also change:

     XTAU = GET_TAU0( 1, 1, GET_YEAR() )
and
     XTAU = GET_TAU0( GET_MONTH(), 1, GET_YEAR() )

to:

     XTAU = GET_TAU0( 1, 1, YEAR )
and
     XTAU = GET_TAU0( GET_MONTH(), 1, YEAR )

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

Outstanding Issues

None reported so far.

--Bob Y. 14:07, 30 March 2012 (EDT)