Tagged CO simulation

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The tagged CO simulation is an offline simulation that calculates CO concentrations only. It uses monthly mean OH concentrations archived from a previous full-chemistry simulation (more on that below). Because the simulation is linear, CO can be “tagged” by its source region/type. The regions and types used can be adapted to address different problems with a few simple code modifications.


1. The tagged CO simulation doesn’t include direct emissions of volatile organic compounds (VOCs), so CO sources are scaled to account for co-emitted VOCs. Fossil fuel and biofuel emissions are scaled by 19% and biomass burning emissions are scaled by 11%. More information is given in Duncan et al. (2007).

2. Biogenic VOCs:

  a. Isoprene: Yield of CO from isoprene is assumed to be 30% based on Miyoshi et al. (1994). Isoprene yield can also be computed as a
function of NOx concentration by setting ALPHA_ISOP_FROM_NOX = .TRUE. in CHEM_TAGGED_CO, but this is not the default behavior. b. Methanol: The CO flux from methanol is scaled to the isoprene flux c. Monoterpene: Yield of CO from monoterpenes is assumed to be 20% based on Hatakeyama et al. (1991) and Vinckier et al. (1998). d. Acetone: Yield of CO from acetone is assumed to be 2/3 and accounts for acetone loss from reaction with OH and photolysis.

3. OH concentrations are taken from a much earlier version of the model, when they were thought to be more realistic. The standard code uses OH from version 5-07-08.

4. Methane concentrations are calculated based on measurements from the NOAA Global Monitoring Division network and are assumed constant over four latitudinal bands (30-90S, 0-30S, 0-30N, 30-90N). Yield is assumed to be one molecule CO per molecule CH4.

Standard Tracers

In a standard run, there are 17 tracers (see input.geos below).

Tracer 1 (CO) is total CO; this is the sum of CO from all sources.
Tracers 2-5 are CO from fossil fuel emissions in: 
 -COus: North America (172.5-17.5W, 24-88N)
 -COeur: Europe (17.5W-72.5E, 36-45N and 17.5W-172.5E, 45-88N)
 -COasia: Asia (70-152.5E, 8-45N)
 -COoth: everywhere else.
Tracers 6-11 are CO from biomass burning emissions in:
 -CObbam: South America (112.5-32.5W, 56S-24N)
 -CObbaf: Africa (17.5W-70E, 48S-36N)
 -CObbas: Southeast Asia (70-152.5E, 8-45N)
 -CObboc: Oceania (70-170E, 90S-8N)
 -CObbeu: Europe (17.5W-72.5E, 36-45N and 17.5W-172.5E, 45-88N)
 -CObbna: Everywhere else (basically North America)
Tracer 12 (COch4) is CO produced from methane.
Tracer 13 (CObiof) is CO from biofuel emissions (except if you are using the Streets inventory over Asia, where biofuel and fossil 
fuel emissions are combined). Tracers 14-17 are CO produced from the following volatile organic compounds (in order): isoprene (COisop), monoterpenes (COmono), methanol
(COmeoh), and acetone (COacet).

The regional definitions used for the fossil fuel and biomass burning tracers can be changed in DEFINE_FF_REGIONS and DEFINE_BB_REGIONS, respectively. The biofuel tracer can be removed by commenting lines in EMISS_TAGGED_CO (look for LSPLIT and tracer #13). The methane and VOC tracers can be removed by commenting lines in CHEM_TAGGED_CO (look for LSPLIT). Note that if you change the tracers you will also need to make the appropriate changes in your input.geos and restart files.


Tagged CO is simulation type 7. For tagged CO run with standard tracers, the input.geos should look like this:

%%% TRACER MENU %%%     : 
Type of simulation      : 7 
Number of Tracers       : 17  
Tracer Entries -------> : TR#   Name    g/mole Tracer Members; () = emitted  
Tracer #1               : 1     CO      28.0   (CO) 
Tracer #2               : 2     COus    28.0  
Tracer #3               : 3     COeur   28.0  
Tracer #4               : 4     COasia  28.0  
Tracer #5               : 5     COoth   28.0  
Tracer #6               : 6     CObbam  28.0  
Tracer #7               : 7     CObbaf  28.0  
Tracer #8               : 8     CObbas  28.0  
Tracer #9               : 9     CObboc  28.0  
Tracer #10              : 10    CObbeu  28.0  
Tracer #11              : 11    CObbna  28.0  
Tracer #12              : 12    COch4   28.0  
Tracer #13              : 13    CObiof  28.0  
Tracer #14              : 14    COisop  28.0  
Tracer #15              : 15    COmono  28.0  
Tracer #16              : 16    COmeoh  28.0  
Tracer #17              : 17    COacet  28.0

Recent tagged CO updates

1. Updated CO+OH rate constant to JPL2006 (Jenny Fisher): will be standard in v8-02-03
2. Optional use of MEGAN biogenic emissions added (Prasad Kasibhatla and Jenny Fisher): will be standard in v8-02-03

Tagged CO development projects

1. Flexible region masks (Dylan Jones and Prasad Kasibhatla)

More Information

For more information, see the GEOS-Chem manual pages about tagged CO:



1. Duncan, B. N., Logan, J. A., Bey, I., Megretskaia, I. A., Yantosca, R. M., Novelli, P. C., Jones, N. B., and Rinsland, C. P.: Global budget of CO, 1988–1997: Source estimates and validation with a global model, J. Geophys. Res., 112, D22301, doi:10.1029/2007JD008459, 2007.
2. Hatakeyama, S., Izumi, K., Fukuyama, T., Akimoto, H. Washida, N.: Reactions of OH with alpha-pinene and beta-pinene in air: Estimate of global CO production from the atmospheric oxidation of terpenes, J. Geophys. Res., 96(D1), 947-958, 1991.
3. Miyoshi, A., Hatakeyama, S., Washida, N.: OH radical-initiated photooxidation of isoprene: An estimate of global CO production, J. Geophs. Res., 99(D9), 18779-18787, 1994.
4. Vinckier, C., Compernolle, F., Saleh, A. M., Van Hoof, N., Van Hees, I.: Product yields of the alpha -pinene reaction with hydroxyl radicals and the implication on the global emission of trace compounds in the atmosphere, Fresenius Env. Bull., 7(5-6), 361-368, 1998.