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Influence of bromine and iodine chemistry on annual, seasonal, diurnal, and background ozone: CMAQ simulations over the Northern Hemisphere
Citation:
Sarwar, G., B. Gantt, K. Foley, K. Fahey, T. Spero, D. Kang, R. Mathur, H. Foroutan, J. Xing, T. Sherwen, AND A. Saiz-Lopez. Influence of bromine and iodine chemistry on annual, seasonal, diurnal, and background ozone: CMAQ simulations over the Northern Hemisphere. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 213:395-404, (2019). https://doi.org/10.1016/j.atmosenv.2019.06.020
Impact/Purpose:
Detailed bromine and iodine chemistry is incorporated into the hemispheric CMAQ model. Annual model simulations are conducted without and with the detailed bromine and iodine chemistry. Model results suggests that the bromine and iodine chemistry reduces ozone over seawater and land, and improves model performance. To reduce computational burden of the model, a simple first-oder effective rate constant for the bromine and iodine chemistry mediated ozone loss is also developed.
Description:
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.
URLs/Downloads:
DOI: Influence of bromine and iodine chemistry on annual, seasonal, diurnal, and background ozone: CMAQ simulations over the Northern Hemisphere