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Impact of bromine, iodine, and DMS chemistry on air quality
Citation:
Sarwar, G. Impact of bromine, iodine, and DMS chemistry on air quality. Department of Environmental Science and Engineering, Shanghai, CHINA, November 07, 2018.
Impact/Purpose:
Halogen chemistry is updated in the CMAQv53 model. Dimethyl sulfide chemistry is also included in the CMAQv53 model. The presentation describes the updated halogen chemistry as well as DMS chemistry and their impacts on model results.
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 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 ozone over seawater by 25%, with lower ozone reductions over land. Model results suggest that the chemistry modulates intercontinental transport and lowers the background ozone imported to the United States. While the chemistry is active throughout the year, it does not have a strong seasonal influence on ozone over the Northern Hemisphere. The model shows a minimum diurnal ozone over seawater during daytime, with this minimum further reduced by the bromine and iodine chemistry. 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).