12. Simulations of Emissions, Air Quality, and Climate Contribution in Southeast Asia for March and December

Air pollution is a major concern over Southeast Asia, especially in March when biomass burning and anthropogenic emissions both contribute significantly to air quality in terms of gases and aerosols. This work explores the sensitivity of air quality in terms of ozone in Southeast Asia from future emissions and climate. Simulations with the Nested Regional Climate Model coupled with Chemistry (NRCM-Chem) with 60 and 12 km grid sizes were performed for March and December during 2030–2034 and present day (2005–2009). The NRCM-Chem model employs initial and boundary conditions from the Community Climate System Version 3 (CCSM3) for meteorological variables and Community Atmospheric Model with Chemistry (CAM-Chem) for chemical species. The emission inventories include anthropogenic, biogenic, and biomass burning emissions. The future anthropogenic emissions are the RCP4.5 scenario from CAM-Chem emissions, while biomass burning emissions are the same in both present-day and 2030–2034 simulations. Three simulations were conducted for: (1) present day (2005–2009), (2) future day using the RCP4.5 climate scenario and present anthropogenic emission, and (3) future day using the RCP4.5 climate scenario and future anthropogenic emission. We find, by comparing the NRCM-Chem results with the CAM-Chem results (at a coarser grid spacing of ~200 km), that the two model results have a similar spatial pattern in the present day over Southeast Asia, and they agree fairly well compared to ground-based observations from Pollution Control Department in Thailand. Model results indicate that climate change alone increases ozone concentrations by about 30% in Southeast Asia, while the combination of climate and emission changes in the future increase ozone by another 10% compared to the simulation with only future climate change.