CMAQv5.1 Halogen chemistry

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Brief Description

Recent studies suggest that halogen chemistry can affect ozone over marine environments. We incorporated a detailed bromine and iodine chemistry into the hemispheric CMAQ model and performed model simulation for summer months without and with the detailed halogen chemistry. Using these results, we developed a condensed halogen chemistry and incorporated it into CMAQv5.1 for calculating halogen mediated ozone loss over marine environments. The condensed halogen chemistry is used in CMAQv5.1 for maintaining computational efficiency.

Significance and Impact

A month-long tests were performed without and with the condensed halogen chemistry. The halogen chemistry reduces monthly mean ozone by up to 5.0 ppbv over marine environments.

No significant impact on model run time is expected.

Affected files

Modified files:

  • /MECHS/cb05*_ae6_aq/mech*def
  • /MECHS/cb05*_ae6_aq/RXNS_DATA_MODULE.F90
  • /MECHS/cb05*_ae6_aq/RXNS_FUNC_MODULE.F90
  • /MECHS/saprc07t*_ae6*aq/mech*def
  • /MECHS/saprc07t*_ae6*aq/RXNS_DATA_MODULE.F90
  • /MECHS/saprc07t*_ae6*aq/RXNS_FUNC_MODULE.F90
  • /MECHS/racm2_ae6_aq/mech.def
  • /MECHS/racm2_ae6_aq/RXNS_DATA_MODULE.F90
  • /MECHS/racm2_ae6_aq/RXNS_FUNC_MODULE.F90

Note that the asterisk symbol denotes a wildcard string.


Sarwar, G., B. Gantt, D. Schwede, K. Foley, R. Mathur, and A. Saiz-Lopez: Impact of enhanced ozone deposition and halogen chemistry on tropospheric ozone over the Northern Hemisphere, Environmental Science & Technology, 49(15):9203-9211, (2015).


Golam Sarwar, National Exposure Research Laboratory, U.S. EPA