Influence of bromine and iodine chemistry on annual, seasonal, diurnal, and background ozone: CMAQ simulations over the Northern Hemisphere

Golam Sarwar*, Brett Gantt, Kristen Foley, Kathleen Fahey, Tanya L. Spero, Daiwen Kang, Rohit Mathur, Hosein Foroutan, Jia Xing, Tomás Sherwen, Alfonso Saiz-Lopez

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Bromine and iodine chemistry has been updated in the Community Multiscale Air Quality (CMAQ) model to better capture the influence of natural emissions from the oceans on ozone concentrations. Annual simulations were performed using the hemispheric CMAQ model without and with bromine and iodine chemistry. Model results over the Northern Hemisphere show that including bromine and iodine chemistry in CMAQ not only reduces ozone concentrations within the marine boundary layer but also aloft and inland. Bromine and iodine chemistry reduces annual mean surface ozone over seawater by 25%, with lesser ozone reductions over land. The bromine and iodine chemistry decreases ozone concentration without changing the diurnal profile and is active throughout the year. However, it does not have a strong seasonal influence on ozone over the Northern Hemisphere. Model performance of CMAQ is improved by the bromine and iodine chemistry when compared to observations, especially at coastal sites and over seawater. Relative to bromine, iodine chemistry is approximately four times more effective in reducing ozone over seawater over the Northern Hemisphere (on an annual basis). Model results suggest that the chemistry modulates intercontinental transport and lowers the background ozone imported to the United States.

Original languageEnglish
Pages (from-to)395-404
Number of pages10
JournalAtmospheric Environment
Early online date11 Jun 2019
Publication statusPublished - 15 Sept 2019

Bibliographical note

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  • Background ozone
  • Bromine
  • CMAQ
  • Iodine
  • Ozone

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