Intercomparison of air quality simulations in 2019 using three chemical transport models

Strong air pollution control policies have been implemented to reduce health damage from heavy air pollution, but the PM2.5 concentration level is still high in Southeast Asia. This study aims to identify the causes of air pollution in East Asia using chemical transport models (CTMs). Using three CTMs (CMAQ, WRF-Chem, and GEOS-Chem), air quality was simulated by season in 2019 in Northeast Asia including China and Korea. The prediction performance of PM2.5 and its major components was evaluated, and the causes affecting the difference between CTMs were analyzed, and ways to improve the prediction performance were considered. The 2019 emission inventory updated to reflect recent changes in air pollution emissions was used in common for all three models.

As a result of analyzing the total mass concentration of simulated PM2.5 and major chemical components, the performance of each model was different for each season. CMAQ in January, WRF-Chem in July, and GEOS-Chem in October tended to overestimate the PM2.5 concentrations. For CMAQ, secondary organic aerosol (SOA) was produced by semivolatile/intermediate-volatility organic compounds (S/IVOC), and PM2.5 concentrations was high in winter. This is because CMAQ includes a new pathway for potential combustion secondary organic aerosol (pcSOA). Also, WRF-Chem simulated a particularly high concentration of sulfate because it affected the scavening function according to the aqueous phase chemistry.

These multi-model intercomparison of air quality simulations will be helpful in future research to increase understanding of the differences between CTMs in Northeast Asia and to identify the causes of air pollution.